Journal Cover Tetrahedron Letters
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   ISSN (Print) 0040-4039 - ISSN (Online) 1359-8562
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  • Solvent- and environment-dependent fluorescence of modified nucleobases
    • Authors: Kohji Seio; Takashi Kanamori; Yoshiaki Masaki
      Pages: 1977 - 1985
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Kohji Seio, Takashi Kanamori, Yoshiaki Masaki
      Fluorescent nucleosides with modified nucleobases are useful tools for detecting nucleic acids and probing their structures and functions. Nucleobases are suitable for modification because 1) intrinsically light-absorbing nucleobases can be converted to fluorescent chromophores by simple chemical modification, 2) attaching substituents to nucleobases at appropriately selected positions does not inhibit base pairing or duplex formation, and 3) duplex formation and protein interactions affect the environment of nucleobases, causing changes in their fluorescence intensities and/or wavelengths. This review summarizes recent fluorescent nucleosides and their photophysical properties, such as absorption wavelength, emission wavelength, and fluorescence quantum yield together with their solvent dependency.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.003
       
  • Chitosan-supported copper as an efficient and recyclable heterogeneous
           catalyst for A3/decarboxylative A3-coupling reaction
    • Authors: Pavneet Kaur; Bhupinder Kumar; Vinod Kumar; Rakesh Kumar
      Pages: 1986 - 1991
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Pavneet Kaur, Bhupinder Kumar, Vinod Kumar, Rakesh Kumar
      Chitosan-supported copper (chit@copper) based heterogeneous catalysts have been explored for A3-coupling and decarboxylative A3-coupling. The developed protocol employs low catalyst loading, solventless condition and easy work-up for the synthesis of diversely substituted propargylamines. More importantly, the catalyst could be recovered and reused without any significant loss in the activity. This offer huge advantages as recyclability issues are rarely addressed in decarboxylative A3-coupling. Leaching studies were carried out using AAS and ICPMS analysis. It is envisaged that chit@copper catalysts can have potential applications in terms of efficiency and recyclability in the emerging area of decarboxylative CH bond activation/functionalization strategies.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.03.053
       
  • 12-Deoxyroridin J and 12-Deoxyepiisororidin E from Calcarisporium
           arbuscular
    • Authors: Manami Matsumoto; Shizuya Tanaka; Akio Tonouchi; Masaru Hashimoto
      Pages: 1992 - 1995
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Manami Matsumoto, Shizuya Tanaka, Akio Tonouchi, Masaru Hashimoto
      The culture broth of Calcarisporium arbuscular afforded 12-deoxyroridin J (1) and 12-deoxyepiisororidin E (2). Their structures were elucidated based on NMR and ECD analyses. Both molecules showed negative ECD splitting at 240 nm and a negative Cotton effect at 200 nm. Density functional theory calculations revealed that the former is caused due to the ECD exciton coupling between the C1′–C3′ enone and C7′–C11′ dienone chromophores, whereas the latter corresponds to the longer wavelength fragment of the negative ECD splitting in the vacuum ultraviolet (VUV) region at 190 nm which cannot be observed with conventional circular dichroism spectrometers. Simultaneous isolation of the regular roridins suggested that 1 and 2 are obtained through the same biosynthetic pathway. Since the 12-epoxy functionality is introduced at an early biosynthetic stage, 1 and 2 are assumed to be derived from reductions of the 12,13-epoxide in the corresponding regular roridins at a later biosynthetic stage.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.03.089
       
  • Synthesis of benzyl halide derivatives of spirohydantoins via [2+2+2]
           cyclotrimerization reaction
    • Authors: Sanbasivarao Kotha; Gaddamedi Sreevani
      Pages: 1996 - 1998
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Sanbasivarao Kotha, Gaddamedi Sreevani
      Generally, synthesis of hydantoin derivatives involve use of carbonyl compounds which in turn require multistep synthesis. Here, we report a new approach to assemble spirohydantoins via [2+2+2] cyclotrimerization reaction using commercially available, inexpensive hydantoin as a starting material.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.012
       
  • Asymmetric synthesis of ABC tricyclic core in Daphniphyllum alkaloid
           21-deoxy-macropodumine D
    • Authors: Xiu-Fang Mo; Yun-Fei Li; Ming-Hui Sun; Qiu-Yan Dong; Qin-Xia Xie; Pei Tang; Fei Xue; Yong Qin
      Pages: 1999 - 2004
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Xiu-Fang Mo, Yun-Fei Li, Ming-Hui Sun, Qiu-Yan Dong, Qin-Xia Xie, Pei Tang, Fei Xue, Yong Qin
      In this paper, we describe our efforts toward the asymmetric synthesis of Daphniphyllum alkaloid 21-deoxymacropodumine D which led to efficient preparation of a ABC tricyclic framework containing five consecutive stereocenters. This synthetic work features (1) utilization of an asymmetric conjugate addition to install the C5 all-carbon quaternary center, (2) an intramolecular aza-Michael addition followed by Pd-catalyzed α-alkenylation to build the bowl-shaped tricyclic core.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.019
       
  • Copper-catalyzed C–N coupling/C–H functionalization: A tandem approach
           to azole-fused quinazoline derivatives
    • Authors: Dingben Chen; Ling Huang; Jianguo Yang; Junna Ma; Yingying Zheng; Yi Luo; Yang Shen; Jiashou Wu; Chao Feng; Xin Lv
      Pages: 2005 - 2009
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Dingben Chen, Ling Huang, Jianguo Yang, Junna Ma, Yingying Zheng, Yi Luo, Yang Shen, Jiashou Wu, Chao Feng, Xin Lv
      A Cu-catalyzed tandem synthesis of azole-fused pyrimido[1,2-c]quinazolines and imidazo[1,2-c]quinazolines has been developed. The reaction is based on a C–N cross-coupling/C–H functionalization reaction of 2-(2-bromophenyl)-1,4,5,6-tetrahydropyrimidines with azoles. A variety of the desired polycyclic products were obtained in moderate to excellent yields.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.020
       
  • Influence of steric effects in solid-phase aza-peptide synthesis
    • Authors: Meeli Arujõe; Anu Ploom; Anton Mastitski; Jaak Järv
      Pages: 2010 - 2013
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Meeli Arujõe, Anu Ploom, Anton Mastitski, Jaak Järv
      Aza-peptides are peptide analogs with potential applications as drug candidates. However, due to difficulties associated with the synthesis of these compounds, information regarding their bioactivity is very limited. Herein, we identify steric hindrance as one reason for the slowness of the aza-peptide bond formation reaction. The steric effect of the side group of amino acids in their coupling with the semicarbazide moiety in the synthesis of a model peptide, H-AA-AzAla-Phe-NH2, was studied and quantified using COMU as a coupling reagent. Characterization of the role of this structural factor in aza-peptide bond synthesis is essential for outlining a new and efficient synthesis protocol.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.021
       
  • Metal-free, highly regioselective sulfonylation of NH-1,2,3-triazoles with
           sodium sulfinates and thiosulfonates
    • Authors: Raju Jannapu Reddy; Angothu Shankar; Md. Waheed; Jagadeesh Babu Nanubolu
      Pages: 2014 - 2017
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Raju Jannapu Reddy, Angothu Shankar, Md. Waheed, Jagadeesh Babu Nanubolu
      A convenient and metal-free protocol for the highly regioselective sulfonylation of NH-1,2,3-triazoles is described. A range of readily accessible NH-1,2,3-triazoles were sulfonylated with various aryl sulfinates in the presence of molecular iodine. The scope was extended to thiosulfonates as an efficient sulfonylating agent and nitrochromene derived triazoles were also explored for selective N-sulfonylation. A variety of synthetically viable N 2-sulfonyl triazoles were obtained in moderate to high yields with excellent regioselectivities via N–S bond construction under mild reaction conditions.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.023
       
  • Efficient synthesis of 1,2,4-oxadiazine-5-ones via [3+3] cycloaddition of
           in situ generated aza-oxyallylic cations with nitrile oxides
    • Authors: Gangqiang Wang; Rongxing Chen; Sen Zhao; Liangfeng Yang; Haibing Guo; Shaofa Sun; Jian Wang; Justin Domena; Yalan Xing
      Pages: 2018 - 2020
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Gangqiang Wang, Rongxing Chen, Sen Zhao, Liangfeng Yang, Haibing Guo, Shaofa Sun, Jian Wang, Justin Domena, Yalan Xing
      1,2,4-Oxadiazin-5-ones were prepared via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides in good yields and excellent functional group compatibility. This efficient transformation is metal-free and is promoted by an inorganic base Cs2CO3. In addition, this reaction features simple-operation, mild conditions, and high regioselectivity.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.025
       
  • Dictyoneolone, a B/C ring juncture-defused steroid from a Dictyonella sp.
           sponge
    • Authors: Jung-Kyun Woo; Jung-Ho Yun; Seyeon Ahn; Chung J. Sim; Minsoo Noh; Dong-Chan Oh; Ki-Bong Oh; Jongheon Shin
      Pages: 2021 - 2024
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Jung-Kyun Woo, Jung-Ho Yun, Seyeon Ahn, Chung J. Sim, Minsoo Noh, Dong-Chan Oh, Ki-Bong Oh, Jongheon Shin
      Dictyoneolone (1), a new secosteroid was isolated from a Dictyonella sp. sponge collected from Gageo-do, Korea. Based upon the results of combined spectroscopic analyses, the structure of this compound was determined to possess a highly unusual B/C ring juncture-defused moiety. The configurations of 1 were determined by a combination of proton-proton couplings and NOESY analyses. Dictyoneolone exhibited weak cytotoxicity against the K562 and A549 cancer cell lines.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.026
       
  • Carbonylative Sonogashira annulation sequence: One-pot synthesis of
           4-quinolone and 4H-chromen-4-one derivatives
    • Authors: Prasanjit Ghosh; Aritra Kumar Nandi; Sajal Das
      Pages: 2025 - 2029
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Prasanjit Ghosh, Aritra Kumar Nandi, Sajal Das
      Carbonylative Sonogashira annulation sequence for one pot synthesis of 4-quinolone and 4H-chromen-4-one has been developed in presence of Pd-NHC catalyst. Substituted 2-iodoaniline and 2-iodophenol independently underwent in the carbonylative Sonogashira annulation reaction with a variety of acetylenes to result in 4-quinolone and flavone derivatives respectively in good to excellent yield. Moreover, this protocol does not require toxic CO gas, high catalyst loading and any expensive salt/additive. Herein we, for the first time, are using Mo(CO)6, as solid CO source for the one pot synthesis of flavone derivatives via carbonylative Sonogashira annulation reaction.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.029
       
  • Asymmetric syntheses of
           (R)-4-halo-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines,
           important 5-HT2C agonist precursors
    • Authors: Thomas O. Schrader; Xiuwen Zhu; Michelle Kasem; Sufang Li; Chunyan Liu; Albert Ren; Chunrui Wu; Graeme Semple
      Pages: 2030 - 2033
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Thomas O. Schrader, Xiuwen Zhu, Michelle Kasem, Sufang Li, Chunyan Liu, Albert Ren, Chunrui Wu, Graeme Semple
      Asymmetric syntheses of N-protected (R)-4-halo-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines, advanced intermediates for the synthesis of highly potent and selective 5-HT2C agonists, are described. The key transformation involves ring opening of N-protected bicyclic sulfamidate (R)-hexahydro-3H-pyrazino[1,2-c][1,2,3]oxathiazine 1,1-dioxide with (4-halo-2-fluoropyridin-3-yl)lithiums or (3-bromo-5-fluoropyridin-4-yl)lithium. In situ hydrolyses of the resultant sulfamic acids and subsequent intramolecular nucleophilic aromatic substitutions (SNAr) produce the enantiopure tricycles. The two step procedure represents new methodology for the stereoselective syntheses of tetrahydronaphthyridines.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.030
       
  • Improved organocatalytic electrophilic α-cyanation of β-keto amides with
           1-cyanato-4-nitrobenzene
    • Authors: Pran Gopal Karmaker; Jiashen Qiu; Di Wu; Sule Zhang; Hongquan Yin; Fu-Xue Chen
      Pages: 2034 - 2037
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Pran Gopal Karmaker, Jiashen Qiu, Di Wu, Sule Zhang, Hongquan Yin, Fu-Xue Chen
      By using a readily accessible, new and safe cyano-transfer reagent, 1-cyanato-4-nitrobenzene, the enantioselectivity of the direct electrophilic α-cyanation of 1-indanone-derived β-keto amides was greatly improved as a result of an enhanced double-hydrogen bonding. Thus, in the presence of cinchonine as the bifunctional organocatalyst, a series of α-cyano β-keto amides were produced in excellent yields (73–97%) and good to high enantioselectivities (75–91% ee) under mild reaction conditions.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.032
       
  • Visible-light-mediated cascade difunctionalization/cyclization of
           alkynoates with acyl chlorides for synthesis of 3-acylcoumarins
    • Authors: Yu Liu; Qiao-Lin Wang; Cong-Shan Zhou; Bi-Quan Xiong; Pan-Liang Zhang; Shuang-Jian Kang; Chang-An Yang; Ke-Wen Tang
      Pages: 2038 - 2041
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Yu Liu, Qiao-Lin Wang, Cong-Shan Zhou, Bi-Quan Xiong, Pan-Liang Zhang, Shuang-Jian Kang, Chang-An Yang, Ke-Wen Tang
      A new visible-light-mediated radical cyclization of alkynoates with acyl chlorides is described for the one-pot construction of diverse 3-acylcoumarins with high efficiency and selectivity. This method is successful by sequential difunctionalization of an alkynes CC triple bond with the CCl bonds of acyl chloride and aromatic C(sp2)H bonds. The cyclization is proposed to simultaneously form two new carbon–carbon bonds, and involves radical acylation, 5-exo-trig cyclization, and ester migration.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.033
       
  • Experimental and theoretical studies on rhodium-catalyzed direct CH
           benzoxylation reaction
    • Authors: Chen Jin; Guimin Wang; Xueyan Yang; Weiliang Zhu; Yaxi Yang
      Pages: 2042 - 2045
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Chen Jin, Guimin Wang, Xueyan Yang, Weiliang Zhu, Yaxi Yang
      An efficient Rh(III)-catalyzed, chelation assisted CH benzoxylation reaction has been developed, releasing H2O as the single byproduct. The reaction proceeded under mild conditions, with controllable mono- and dioxygenation selectivity, thus providing a good complement to previous CH oxygenation reactions. DFT calculations support that a nucleophilic addition pathway is most likely involved in the current reaction system.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.034
       
  • The coupling of potassium organotrifluoroborates with Baylis–Hillman
           derivatives via visible-light photoredox catalysis
    • Authors: Hongqiang Ye; Qianwen Ye; Dongping Cheng; Xiaonian Li; Xiaoliang Xu
      Pages: 2046 - 2049
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Hongqiang Ye, Qianwen Ye, Dongping Cheng, Xiaonian Li, Xiaoliang Xu
      Catalyzed by Ir[dF(CF3)ppy]2(dtbbpy)PF6, the coupling of potassium organotrifluoroborates with Baylis–Hillman derivatives under visible light irradiation has been developed. Based on the mechanism of reductive quenching cycle, it provides an easy, mild, efficient method for the synthesis of a variety of α,β-unsaturated carboxylic esters derivatives in a broad scope of the substrates.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.035
       
  • Two pairs of new alkaloid enantiomers with a spiro
           
    • Authors: Zhuo-Yang Cheng; Ye-Qing Du; Qian Zhang; Bin Lin; Pin-Yi Gao; Xiao-Xiao Huang; Shao-Jiang Song
      Pages: 2050 - 2053
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Zhuo-Yang Cheng, Ye-Qing Du, Qian Zhang, Bin Lin, Pin-Yi Gao, Xiao-Xiao Huang, Shao-Jiang Song
      (±)-Juglanaloid A (1) and B (2), two pairs of novel naturally occurring alkaloid enantiomers bearing an unprecedented spiro [benzofuranone-benzazepine] skeleton, were isolated from the bark of Juglans mandshurica Maxim. The unusual 6, 5, 7, 6-cyclic system with a rare spiro cyclic center at C-4 was determined on the basis of spectroscopic data. Chiral separation of 1 and 2 yielded two pairs of enantiomers, 1a/1b and 2a/2b. The absolute configurations were established by comparing the experimental and calculated electronic circular dichroism spectra. The potential anti-AD properties of 1a/1b and 2a/2b were evaluated by the Thioflavin T assay.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.037
       
  • Synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives via
           intramolecular CH activation reactions of trichloroacetamidine and
           benzenesulfonyl chloride
    • Authors: Manijeh Nematpour; Elham Rezaee; Mehdi Jahani; Sayyed Abbas Tabatabai
      Pages: 2054 - 2056
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Manijeh Nematpour, Elham Rezaee, Mehdi Jahani, Sayyed Abbas Tabatabai
      The synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives was achieved through a novel three-component intramolecular CH activation reaction of trichloroacetonitrile, benzenesulfonyl chloride, and various primary amines. This reaction was performed in the presence of catalytic copper(I) and l-proline as the ligand in tetrahydrofuran at room temperature.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.038
       
  • Piezofluorochromism of triphenylamine-based triphenylacrylonitrile
           derivative with intramolecular charge transfer and aggregation-induced
           emission characteristics
    • Authors: Xin Wang; Yunhan Wang; Yong Zhan; Peng Yang; Xiaojing Zhang; Yongnan Xu
      Pages: 2057 - 2061
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Xin Wang, Yunhan Wang, Yong Zhan, Peng Yang, Xiaojing Zhang, Yongnan Xu
      New triphenylacrylonitrile derivative (DPPA) with triphenylamine moiety as electron donor group has been synthesized. Its emission wavelengths were strongly affected by solvent polarity, indicating intramolecular charge transfer (ICT) transitions. It was found that DPPA was almost non-emissive in tetrahydrofuran (THF), and the emission could be intensified obviously when a great amount of H2O was added, illustrating aggregation induced emission property. It is interesting that the pristine crystal of DPPA emitted green light, and the ground made its emitting color to change into orange, which could be recovered under fumed with dichloromethane (DCM) vapor. The piezofluorochromic behavior might be switched reversibly under the stimulus of external force because of crystalline-amorphous phase transformation, which could be confirmed from the results of PXRD patterns and DSC curves in different solid states. This work might open a new strategy to provide a broad perspective for the development of AIE PFC materials.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.039
       
  • Visible light-promoted metal-free aerobic oxyphosphorylation of olefins: A
           facile approach to β-ketophosphine oxides
    • Authors: Yun Shi; Rongshun Chen; Kang Guo; Fei Meng; Shujun Cao; Chen Gu; Yingguang Zhu
      Pages: 2062 - 2065
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Yun Shi, Rongshun Chen, Kang Guo, Fei Meng, Shujun Cao, Chen Gu, Yingguang Zhu
      A metal-free direct aerobic oxyphosphorylation of alkenes with H-phosphine oxides has been developed utilizing visible light photoredox catalysis. A variety of β-ketophosphine oxides have been obtained in good yields from simple olefins under air with inexpensive rhodamine B as the non-metallic photocatalyst. This method provides a mild, green, and practical synthetic approach to valuable β-ketophosphine oxides.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.040
       
  • Antimicrobial indole alkaloids with adductive C9 aromatic unit from
           Gelsemium elegans
    • Authors: Xin Wei; Jing Yang; Hong-Xia Ma; Cai-Feng Ding; Hao-Fei Yu; Yun-Li Zhao; Ya-Ping Liu; Afsar Khan; Yi-Fen Wang; Zi-Feng Yang; Wan-Yi Huang; Xin-Hua Wang; Xiao-Dong Luo
      Pages: 2066 - 2070
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Xin Wei, Jing Yang, Hong-Xia Ma, Cai-Feng Ding, Hao-Fei Yu, Yun-Li Zhao, Ya-Ping Liu, Afsar Khan, Yi-Fen Wang, Zi-Feng Yang, Wan-Yi Huang, Xin-Hua Wang, Xiao-Dong Luo
      Gelselegandines A-C (1–3), three unprecedented gelsedines incorporating additional C9 aromatic unit as side chain, were isolated from Gelsemium elegans. Their structures were elucidated by means of spectroscopic techniques and electronic circular dichroism (ECD) calculation. Additionally, gelselegandines A–C showed moderate antimicrobial activities against four bacterial strains and two fungi.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.041
       
  • Direct synthesis of β-ketophosphine oxides via copper-catalyzed
           difunctionalization of alkenes with H-phosphine oxides and dioxygen
    • Authors: Guangming Nan; Huilan Yue
      Pages: 2071 - 2074
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Guangming Nan, Huilan Yue
      A simple copper-catalyzed direct difunctionalization of alkenes with H-phosphine oxides and dioxygen for the synthesis of β-ketophosphine oxides has been developed under mild conditions. The present protocol, which utilizes an inexpensive catalyst, readily available materials, and environmentally benign oxygen source, provides a convenient and cost-effective approach to construct various β-ketophosphine oxides.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.042
       
  • Metal/catalyst/reagent free hydration of alkynes up to gram scale under
           temperature and pressure controlled condition
    • Authors: Munsaf Ali; Avinash K. Srivastava; Raj K. Joshi
      Pages: 2075 - 2078
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Munsaf Ali, Avinash K. Srivastava, Raj K. Joshi
      A new green water-mediated metal/catalyst/reagent-free methodology for hydration of alkyne is devised. The remarkable yields of various ketones were achieved when alkynes were heated at 150 °C under 11 bar pressure in an autoclave for 14 h in water-methanol solution. Outstanding functional group compatibility for both the terminal and internal alkynes was established. This methodology produces excellent yields up to gram scale under optimised reaction condition.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.044
       
  • Green synthesis of ethyl oxalate benzylidinyl hydrazides
    • Authors: Zhi Xiang Zhao; Li Ping Cheng; Wan Pang
      Pages: 2079 - 2081
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Zhi Xiang Zhao, Li Ping Cheng, Wan Pang
      Acylhydrazone compounds play an important role in medicine, materials and other fields. Herein we report the synthesis of ethyl oxalate benzylidinyl hydrazides by the reaction of benzaldehyde derivatives and ethyl oxalate hydrazide under catalyst-free conditions in H2O near room temperature. This green synthesis method has the advantages of mild reaction conditions, fast reaction rate, non-catalytic, good yield and easy isolation. These synthesized ethyl oxalate benzylidinyl hydrazides can be used as Schiff base metal complexes of small molecule ligands.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.047
       
  • The tertiary-butyl group: Selective protection of the anomeric centre and
           evaluation of its orthogonal cleavage
    • Authors: Afraz Subratti; Nigel Kevin Jalsa
      Pages: 2082 - 2085
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Afraz Subratti, Nigel Kevin Jalsa
      The tertiary-butyl group has not been examined extensively as a protecting group. In this work, we describe the synthesis of tert-butyl glycosides via the Fischer glycosylation protocol. Furthermore, its utility as a temporary anomeric protecting group was evaluated. A range of differentially protected monosaccharides was used to investigate the stability of the tert-butyl group upon the introduction of other protecting groups; and compatibility of its cleavage in the presence of the latter.
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      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.048
       
  • Lipase-catalyzed amidation of carboxylic acid and amines
    • Authors: Daniela Manova; Florian Gallier; Lotfi Tak-Tak; Lyubov Yotava; Nadège Lubin-Germain
      Pages: 2086 - 2090
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Daniela Manova, Florian Gallier, Lotfi Tak-Tak, Lyubov Yotava, Nadège Lubin-Germain
      The amidation reaction is of a very particular interest, especially in the pharmaceutical industry and always requires the activation of the acid with a large excess of reactants. Therefore, a large amount of waste is generated. In order to reduce the environmental impact of such reaction, we have developed enzymatic amidation conditions which are compatible with a wide range of amines and acids, in particular with the biologically relevant lipoic acid. Water is the only by-product generated during this reaction thus a very high atom economy is obtained. In addition, we have shown that the lipase can be recovered and reused several times without a significant loss of activity.
      Graphical abstract image

      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.049
       
  • A diastereoselective Mannich reaction of α-fluoroketones with ketimines:
           Construction of β-fluoroamine motifs with vicinal tetrasubstituted
           stereocenters
    • Authors: Jian-bo Zhao; Xinfeng Ren; Bu-quan Zheng; Jian Ji; Zi-bin Qiu; Ya Li
      Pages: 2091 - 2094
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Jian-bo Zhao, Xinfeng Ren, Bu-quan Zheng, Jian Ji, Zi-bin Qiu, Ya Li
      A diastereoselective Mannich reaction has been developed for the synthesis of chiral β-fluoroamine motifs by the reaction of α-fluoroketones with ketimines, including isatin-derived ketimines and phenylglyoxylate-derived ketimines. This method provides a concise route to a variety of biologically important 3-aminooxindoles and α-amino acids featuring fluorine-containing vicinal tetrasubstituted stereocenters.
      Graphical abstract image

      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.051
       
  • Sky-blue phosphorescent organic light-emitting diode with superior
           performance based on novel chlorine functionalized iridium(III) complex
    • Authors: Long Gao; Peng Tao; Yanqin Miao; Wei Jia; Yaping Zhao; Hua Wang; Bingshe Xu
      Pages: 2095 - 2098
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Long Gao, Peng Tao, Yanqin Miao, Wei Jia, Yaping Zhao, Hua Wang, Bingshe Xu
      A novel and highly efficient chlorine functionalized iridium(III) complex is designed and synthesized. The complex shows intensive sky-blue phosphorescence (with a peak of 492 nm and a shoulder at 524 nm), high photoluminescence efficiency (0.78) and moderate full width at half maximum (62 nm). The aromatic chlorine introduced into the complex provides the robust chemical stability and effective sky-blue phosphorescence for organic light-emitting diodes (OLEDs). The maximum power efficiency, current efficiency and external quantum efficiency for the complex based OLED are up to 48.46 lm/W, 55.04 cd/A and 18.47%, respectively.
      Graphical abstract image

      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.053
       
  • Metal-free oxidative cyclization of 2-amino-benzamides,
           2-aminobenzenesulfonamide or 2-(aminomethyl)anilines with primary alcohols
           for the synthesis of quinazolinones and their analogues
    • Authors: Jinwei Sun; Tao Tao; Dan Xu; Hui Cao; Qinggang Kong; Xinyu Wang; Yun Liu; Jianglin Zhao; Yi Wang; Yi Pan
      Pages: 2099 - 2102
      Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21
      Author(s): Jinwei Sun, Tao Tao, Dan Xu, Hui Cao, Qinggang Kong, Xinyu Wang, Yun Liu, Jianglin Zhao, Yi Wang, Yi Pan
      A general metal-free oxidative cyclization process has been developed for the synthesis of quinazolinones, benzothiadiazines and quinazolines. By this protocol, a range of substituted 2-aminobenzamides, 2-aminobenzenesulfonamide and 2-(aminomethyl)anilines react with various alcohols, leading to the desired annulated products smoothly. This protocol features many advantages as broad substrate scope, mild reaction conditions, low environmental pollution, high atom-economy and good to excellent yields.
      Graphical abstract image

      PubDate: 2018-05-02T11:53:58Z
      DOI: 10.1016/j.tetlet.2018.04.054
       
  • Recent developments in the synthesis of prosophylline and its derivatives
    • Authors: C. Ande; S. Dubbu; A.K. Verma; Y.D. Vankar
      Pages: 1879 - 1895
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): C. Ande, S. Dubbu, A.K. Verma, Y.D. Vankar
      Several synthetic efforts are reported towards the optically active (−)-prosophylline and (+)-prosophylline, and their derivatives. Interestingly and surprisingly, although only a few synthesis are reported for the parent molecules, there are more reports for the synthesis of their derivatives such as deoxoprosophyllines, deoxoprosopinines, deoxocassines etc. The three main strategies to procure these molecules in optically pure forms are by using (i) chiral synthons (ii) chiral auxiliaries and (iii) asymmetric catalysis. Among these, the chiral synthons are mainly utilized by a number of researchers. This review summarizes the recent developments in the synthesis of optically active prosophyllines and their derivatives, and covers the literature from the year 2000 onwards.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.004
       
  • An improved procedure for the Beckmann rearrangement of cyclobutanones
    • Authors: Mathilde Lachia; François Richard; Raphael Bigler; Amandine Kolleth-Krieger; Michael Dieckmann; Alexandre Lumbroso; Ulfet Karadeniz; Saron Catak; Alain De Mesmaeker
      Pages: 1896 - 1901
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Mathilde Lachia, François Richard, Raphael Bigler, Amandine Kolleth-Krieger, Michael Dieckmann, Alexandre Lumbroso, Ulfet Karadeniz, Saron Catak, Alain De Mesmaeker
      γ-Lactams are important building blocks for the synthesis of biologically active molecules and can easily be accessed via Beckmann rearrangement of cyclobutanones. However, Beckmann fragmentation is often a competing reaction for these strained ketones. We found that performing the Beckmann rearrangement with Tamura’s reagent in the presence of aqueous HCl suppresses the undesired fragmentation reaction. This improved procedure was applied to a broad scope of substrates affording monocyclic, bicyclic, tricyclic or spirocyclic lactams. Our experimental results and DFT calculations suggest that the mechanism of the rearrangement probably involves a tetrahedral intermediate and doesn’t proceed via oxime fragmentation as in a classical Beckmann rearrangement.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.012
       
  • Selective cleavage of the N-propargyl group from sulfonamides and amides
           under ruthenium catalysis
    • Authors: Jingjing Wang; Feng Li; Wenlong Pei; Mixue Yang; Yidan Wu; Danyang Ma; Furong Zhang; Jianhui Wang
      Pages: 1902 - 1905
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Jingjing Wang, Feng Li, Wenlong Pei, Mixue Yang, Yidan Wu, Danyang Ma, Furong Zhang, Jianhui Wang
      The selective cleavage of the N-propargyl group from sulfonamides and amides under ruthenium catalysis is described. The reaction tolerates a broad range of functional groups, and the desired products were obtained in 10–95% yield.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.046
       
  • Synthesis of functionalized iodoalkenes using a multicomponent reaction
           triggered by electrophilic iodination of alkenyldiazoacetates
    • Authors: Ryota Kajihara; Shingo Harada; Jun Ueda; Tetsuhiro Nemoto
      Pages: 1906 - 1908
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Ryota Kajihara, Shingo Harada, Jun Ueda, Tetsuhiro Nemoto
      Diazo compounds are frequently used as precursors of metal carbenoids and act as soft nucleophiles even without the use of metal catalysts. The resulting diazonium species may also be trapped by various nucleophiles. The introduction of an iodine functionality applicable for the coupling reaction into an alkenyl diazo compound, however, has not been reported. We developed iodoalkoxylation reactions of alkenyl diazoacetates using an electrophilic iodinating reagent and oxygen nucleophile. This catalyst-free multicomponent reaction proceeded regioselectively, furnishing trisubstituted vinyl iodides in 31%–71% yield. The synthesized iodoalkenes were converted into the corresponding olefins with various functionalities in good yield via Suzuki-Miyaura coupling reactions with arylboronic acids under palladium catalysis to demonstrate the synthetic utility of the developed reaction sequence.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.063
       
  • Pileamartines A and B: Alkaloids from Pilea aff. martinii with a new
           carbon skeleton
    • Authors: Ai Doan Thi Thuy; Van Trinh Thi Thanh; Huong Doan Thi Mai; Huyen Tram Le; Marc Litaudon; Van Minh Chau; Van Cuong Pham
      Pages: 1909 - 1912
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Ai Doan Thi Thuy, Van Trinh Thi Thanh, Huong Doan Thi Mai, Huyen Tram Le, Marc Litaudon, Van Minh Chau, Van Cuong Pham
      Two novel alkaloids, with an unprecedented carbon skeleton, pileamartines A (1) and B (2), together with the known alkaloid, julandine (I-a) were isolated from the alkaloidal fraction of Pilea aff. martinii leaves. Their structures were established by spectral data analysis, including MS and 2D NMR. The absolute configurations of 1 and 2 were suggested by comparison of their experimental and calculated electronic circular dichroism spectra. Compound 2 exhibited weak inhibitory activity against the α-glucosidase enzyme with an inhibition of 11% at a concentration of 200 µM. These compounds were not cytotoxic against several cancer cell lines even at a concentration of 150 µM.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.070
       
  • Halogenated cladosporols produced by the sodium halide-supplemented
           fermentation of the plant-associated fungus Cladosporium sp. TMPU1621
    • Authors: Hiroyuki Yamazaki; Akiho Yagi; Masanari Akaishi; Ryota Kirikoshi; Ohgi Takahashi; Tatsuki Abe; Satomi Chiba; Kenta Takahashi; Natsuki Iwakura; Michio Namikoshi; Ryuji Uchida
      Pages: 1913 - 1915
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Hiroyuki Yamazaki, Akiho Yagi, Masanari Akaishi, Ryota Kirikoshi, Ohgi Takahashi, Tatsuki Abe, Satomi Chiba, Kenta Takahashi, Natsuki Iwakura, Michio Namikoshi, Ryuji Uchida
      A new cladosporol derivative, 2-chloro-cladosporol D (6), was isolated together with known cladosporol (1), cladosporols B–D (2–4), and cladosporol F (5) from the culture broth of plant-associated Cladosporium sp. TMPU1621. The structure of 6 was elucidated from spectroscopic analyses including NMR and MS data. The productivity of 6 increased in 3% NaCl-supplemented medium; therefore, fermentation of the producing fungus TMPU1621 with 3% NaBr was investigated, leading to the induced production of a new halogenated cladosporol, 2-bromo-cladosporol D (7). Compound 2 showed the lowest MIC values of 3.13 and 12.5 μg/mL against two MRSA strains, ATCC43300 and ATCC700698, respectively.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.082
       
  • A highly diastereoselective [3+3] annulation reaction of aza-oxyallyl
           cations and nitrones
    • Authors: Rongxing Chen; Shaofa Sun; Gangqiang Wang; Haibin Guo
      Pages: 1916 - 1920
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Rongxing Chen, Shaofa Sun, Gangqiang Wang, Haibin Guo
      An efficient synthesis of 1,2,4-oxadiazinan-5-ones via [3+3] cycloaddition of in situ generated aza-oxyallyl cations with nitrones has been developed. The protocol features easy operation, excellent yields, excellent diastereo-control, broad substrate scope and good functional group tolerance.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.085
       
  • Sobralene, a new sex-aggregation pheromone and likely shunt metabolite of
           the taxadiene synthase cascade, produced by a member of the sand fly
           Lutzomyia longipalpis species complex
    • Authors: Matthew J. Palframan; Krishna K. Bandi; James G.C. Hamilton; Gerald Pattenden
      Pages: 1921 - 1923
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Matthew J. Palframan, Krishna K. Bandi, James G.C. Hamilton, Gerald Pattenden
      A new sex-aggregation pheromone, sobralene, produced by the sand fly Lutzomyia longipalpis from Sobral (Ceará State, Brazil) is shown to have the novel 6,12-membered ring-fused diterpene structure 3. It is proposed that sobralene is a likely shunt metabolite of the taxadiene synthase-catalysed cyclisation of geranygeranyl diphosphate.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.088
       
  • Catalyst-free synthesis of 1,2,4,5-tetrasubstituted imidazoles from
           arylamins, benzonitriles, arylglyoxals, and Meldrum’s acid
    • Authors: Hossein Mehrabi; Farzaneh Alizadeh-Bami; Reza Ranjbar-Karimi
      Pages: 1924 - 1927
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Hossein Mehrabi, Farzaneh Alizadeh-Bami, Reza Ranjbar-Karimi
      An efficient and catalyst-free for the synthesis of 1,2,4,5-tetrasubstituted imidazoles has been developed using a one-pot, two-step reaction of arylamins, benzonitriles, arylglyoxals, and Meldrum’s acid. All the products were obtained in good to excellent yields and their structures were established from their spectroscopic data.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.093
       
  • CuI catalyzed-novel one-pot synthesis of aryl alkenyl thioethers through
           Ullmann-type coupling reactions using carbon disulfide as a sulfur
           surrogate in the presence of nitroalkanes and aryl iodides
    • Authors: Mehdi Adib; Vahideh Sadeghi; Hojat Veisi
      Pages: 1928 - 1931
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Mehdi Adib, Vahideh Sadeghi, Hojat Veisi
      A mild, general and efficient copper-catalyzed system for C-S bond formation is developed. With CuI as catalyst and l-Proline as ligand, the S-arylation of nitroalkane-CS2 adducts with aryl iodides were performed under mild conditions to give the corresponding products in good to excellent yields.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.092
       
  • Superacid-promoted synthesis of indolizidine derivatives
    • Authors: Sean Kennedy; Anila Kethe; Ahmad Qarah; Douglas A. Klumpp
      Pages: 1932 - 1935
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Sean Kennedy, Anila Kethe, Ahmad Qarah, Douglas A. Klumpp
      A series of amido-acetals were reacted with the Brønsted superacid, CF3SO3H, to provides indolizidine derives by a cyclization cascade. A mechanism is proposed involving formation of a vinylogous enol which undergoes a 6π-electrocyclization reaction with an adjacent N-acyl iminium ion group. With aryl substituents, there is a strong tendency for the N-acyl iminium ion group to undergo Friedel-Crafts type cyclizations with the aryl group. The synthetic methodology was used to prepare the alkaloid natural product, ipalbidine.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.03.094
       
  • One-Pot formation of novel [3+3] NH-CH2 bridged cyclophanes
    • Authors: Yong Huang; Yajing Liu; Song Liu; Renbo Wu; Zehui Wu
      Pages: 1936 - 1939
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Yong Huang, Yajing Liu, Song Liu, Renbo Wu, Zehui Wu
      The new [3+3] NH-CH2 bridged cyclophanes bearing different functional groups and different cavity sizes were prepared in one pot by treating diamine derivatives with dialdehyde derivatives. Factors important for efficiently form-ing these macrocycles include reaction concentration (10 or 100 mmol), temperature (room temperature or 40–50 °C) and solvent (CHCl3). Preliminary fluorescence spectrometer and HRMS-ESI studies demonstrated the inner cavity of the new [3+3] NH-CH2 bridged cyclophanes bearing three hydroxyl groups (3c) as a new highly selective probe for the naked eye detection of Ag+ in PBS buffer.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.005
       
  • Kinetics improvement of protease-mediated formation of pyronin dyes
    • Authors: Sylvain Debieu; Anthony Romieu
      Pages: 1940 - 1944
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Sylvain Debieu, Anthony Romieu
      A fluorescent probe for protease sensing and based on the “covalent-assembly” principle is reported. The basic rational for this unusual class of chemodosimeters proposed by the Anslyn and Yang groups entails the synthesis of non-fluorophore caged precursors full-stable and reactive towards the targeted analyte. Unlike the first generation of protease-sensitive “covalent-assembly” type probes recently published by ourselves (Org. Biomol. Chem. 2017, 15, 2575–2584), the availability of dicyanomethylidenyl and enzyme-labile phenylacetamide moieties within the core structure of mixed bis-aryl ether 2 enables its rapid conversion into a fluorescent pyronin dye at physiological pH and upon activation with penicillin G acylase (PGA). This is real progress towards the practical implementation of this ingenious activation mechanism to the detection of enzymes in their native environment (in cellulo or in vivo).
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.010
       
  • Microwave promoted reaction of purin-6-yl magnesium halides with aldehydes
           in dichloromethane at 100 °C
    • Authors: Malcolm R. Gordon; Stephen D. Lindell
      Pages: 1945 - 1947
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Malcolm R. Gordon, Stephen D. Lindell
      Treatment of a dichloromethane solution of 9-benzyl or 9-phenyl 6-iodopurine with ethereal ethylmagnesium bromide at ambient temperature gives the corresponding purin-6-yl magnesium halides. Addition of an aldehyde followed by heating at 100 °C in a microwave reactor yielded the corresponding carbinols in 52–81% yield.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.014
       
  • Efficient Suzuki-Miyaura mono-arylation of symmetrical
           diiodo(hetero)arenes
    • Authors: Alexander Sapegin; Mikhail Krasavin
      Pages: 1948 - 1951
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Alexander Sapegin, Mikhail Krasavin
      A reliable protocol for converting 1,4-diiodo-2,3,5,6-tetrafluorobenzene into 1-(hetero)aryl-4-iodo-2,3,5,6-tetrafluorobenzene derivatives has been lacking in the literature. We have identified optimal conditions to achieve this conversion in good yields and have minimized formation of the bis-coupling product. The newly identified protocol involving the use of a syringe pump has been extended to other symmetrical diiodo(hetero)arenes.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.015
       
  • A new dimeric imidazole alkaloid plasmid conjugation inhibitor from
           Lepidium sativum
    • Authors: Awo Afi Kwapong; Paul Stapleton; Simon Gibbons
      Pages: 1952 - 1954
      Abstract: Publication date: 16 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 20
      Author(s): Awo Afi Kwapong, Paul Stapleton, Simon Gibbons
      Phytochemical investigation of the methanolic extract of Lepidium sativum seeds led to the isolation of a new compound, named 2-(3-(3-((1H-imidazol-2-yl)methyl)-5-methoxyphenoxy)benzyl)-1H-imidazole and given the trivial name Lepidine AK (1), along with three known compounds; Lepidine E (2), Lepidine B (3) and 2-(3-(2-((1H-imidazol-2-yl)methyl)-6-methoxyphenoxy)benzyl)-1H-imidazole (4). The structures were elucidated based on NMR spectroscopy, UV, IR and high-resolution electrospray ionization mass spectrometry. The isolated compounds were tested for bacterial conjugation inhibition. Lepidine AK (1, 100 μg/mL) reduced the conjugal transfer of the IncI2 plasmid TP114 to 44.7 ± 3.5% but interestingly promoted the conjugation of the IncN plasmid pKM101 to greater than 120%.
      Graphical abstract image

      PubDate: 2018-04-25T05:26:03Z
      DOI: 10.1016/j.tetlet.2018.04.028
       
  • Graphical abstract TOC cont’d
    • Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21


      PubDate: 2018-05-02T11:53:58Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21


      PubDate: 2018-05-02T11:53:58Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 23 May 2018
      Source:Tetrahedron Letters, Volume 59, Issue 21


      PubDate: 2018-05-02T11:53:58Z
       
 
 
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