Tetrahedron Letters

Editorial board ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44
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Graphical Contents List ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44
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A concise total synthesis of lyngbic acid, hermitamides A and B ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): S. Satyanarayana , B.V. Subba Reddy , R. Narender A concise total syntheses of lyngbic acid, hermitamides A and B have been accomplished in a highly enantioselective manner involving CBS asymmetric reduction, hydroboration, and stereospecific Julia–Lythgoe olefination. Graphical abstract image
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Molecular sieves: an efficient and reusable catalyst for multi-component synthesis of dihydropyrano[2,3-C]pyrazole derivatives ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Jitendra B. Gujar , Mahendra A. Chaudhari , Deepak S. Kawade , Murlidhar S. Shingare An efficient synthesis of dihydropyrano[2,3-C]pyrazole derivatives catalyzed by molecular sieves in ethanol under reflux and ultrasound irradiation has been described. The efficiency of catalyst has been compared with other aluminates and silicate based catalyst in order to optimize catalyst for the said organic transformation. This protocol is very useful due to easy recovery of the catalyst and its reusability, short reaction time, excellent yields, and avoidance of environmentally hazardous solvents. Graphical abstract image
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(NH4)2Ce(NO3)6 as an inexpensive, eco-friendly, efficient catalyst for the synthesis of 5-substituted 1-H tetrazoles from nitriles ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Satyanand Kumar , Shristy Dubey , Nisha Saxena , Satish Kumar Awasthi Ceric ammonium nitrate (CAN) is found to be a suitable, inexpensive, and effective non-toxic catalyst for a smooth (3+2) cycloaddition of organic nitriles with NaN3 to afford 5-substituted 1H-tetrazoles in excellent yields. Shorter reaction times, easy work-up, and substantial and pure product formation are the key advantages of the present method. Graphical abstract image
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A new and facile tetrachlorosilane-promoted one-pot condensation for the synthesis of a novel series of tetracyclic 1,5-thiazepines ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Tamer K. Khatab , Khairy A.M. El-Bayouki , Wahid M. Basyouni A new and facile approach for the one-pot synthesis of a novel series of tetracyclic 1,5-thiazepines is described. The reaction occurs through cyclocondensation of fused cyclic ketones, aromatic aldehydes, and 2-aminothiophenol using tetrachlorosilane as a promoter in methylene chloride at ambient temperature. Graphical abstract image
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Total synthesis of lansiumamides A and B and alatamide ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Adele E. Pasqua , Frank D. Ferrari , James J. Crawford , Rodolfo Marquez The total syntheses of lansiumamide A, lansiumamide B and alatamide have been completed taking advantage of the dihalo-olefination of N-formylimides. The syntheses are convergent, flexible and allow for the generation of analogues not accessible through other routes. Graphical abstract image
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Synthesis and fluorescence properties of environment-sensitive 7-(diethylamino)coumarin derivatives ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Stane Pajk By linking 7-(diethylamino)coumarin and different aromatic groups via an oxazole moiety, a small series of new environment-sensitive fluorophores have been synthesized. They display varying degrees of environment-sensitivity, depending on the aromatic group present on the oxazole ring. Additionally, these coumarin-based fluorophores show considerably better photostability compared to the nitrobenzoxadiazole fluorophore, and offer a good starting point for the further development of these fluorophores into environment-sensitive membrane probes or for other applications requiring sensitivity to the environment. Graphical abstract image
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Aza-Ferrier rearrangement of glycals with amides promoted by molecular iodine ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Zubeda Begum , Ch. Kishore , V. Veerabhadra Reddy , B.V. Subba Reddy Amidoglycosidation of tri-O-acetyl-d-glucal with different N-nucleophiles such as t-butyl carbamate, N-benzyl carbamate, N-ethyl carbamate, tosyl amide, and mesyl amide has been achieved using an equimolar amount of molecular iodine under mild and neutral conditions to afford the corresponding N-glycosyl amides in good yields with a preferential α-anomeric selectivity. The use of iodine makes this method simple, convenient, and cost-effective. This is the first report on aza-Ferrier rearrangement using molecular iodine. Graphical abstract image
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Ligand-free palladium assisted insertion of isocyanides to urea derivatives for cascade synthesis of phenylamino-substituted quinazolinones ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Siddharth Sharma , Abhilasha Jain Palladium catalyzed cascade coupling of substituted urea derivatives and tert-butyl isocyanide for the efficient synthesis of phenylamino-substituted quinazolinones has been developed in moderate to good yields. This method provides a short and alternative approach for the synthesis of quinazolinones derivatives which are valuable compounds with biological and pharmacological potentials. A plausible mechanistic scheme is proposed. Graphical abstract image
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Unified flexible total synthesis of chlorofusin and artificial Click mimics as antagonists against p53–HDM2 interactions ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Hai-Bo Qiu , Xin-Ya Chen , Qing Li , Wen-Jian Qian , Shun-Ming Yu , Gong-Li Tang , Zhu-Jun Yao A practical HPLC-free total synthesis of chlorofusin has been successfully accomplished in this work. The new synthesis showed great flexibility and convenience in generating artificial natural product-like mimics through Click chemistry, and enabled us to further investigate the biological importance of the chromophore and the spiro-aminal functionality of the natural product. The entire skeleton is believed to be essential for satisfactory biological activities of both natural chlorofusin and unnatural mimics. Two artificial Click hybrids were found to exhibit improved inhibitory activity against p53–HDM2 bindings over the natural product. Graphical abstract image
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An efficient synthesis of some thiopyranopyrazole-heterocycles via domino reaction in a Brønsted acidic ionic liquid ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Narsidas J. Parmar , Bhagyashri D. Parmar , Tushar R. Sutariya , Rajni Kant , Vivek K. Gupta The thiopyrazole gave many new polycyclic thiopyranopyrazole-heterocycles when it was assembled with a variety of O-alkenylated/alkynylated salicylaldehydes and naphthaldehydes in Brønsted acidic ionic liquid, [Hmim]HSO4, via domino/Knoevenagel–hetero-Diels–Alder (DKHDA) reaction. The reaction is highly stereoselective and the work-up procedure required no chromatography of products in many cases. Graphical abstract image Highlights
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Briarenolide J, the first 12-chlorobriarane diterpenoid from an octocoral Briareum sp. (Briareidae) ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Yin-Di Su , Ching-Hsiao Cheng , Wu-Fu Chen , Yu-Chia Chang , Yu-Hsin Chen , Tsong-Long Hwang , Zhi-Hong Wen , Wei-Hsien Wang , Lee-Shing Fang , Jih-Jung Chen , Yang-Chang Wu , Jyh-Horng Sheu , Ping-Jyun Sung A novel 6,12-dichlorobriarane diterpenoid, briarenolide J (1), was isolated from an octocoral identified as Briareum sp. The structure of briarane 1 was elucidated by spectroscopic methods. Briarenolide J (1) is the first metabolite of a briarane-related natural product found to possess a chlorine atom at C-12 and this compound was found to display inhibitory effects on the generation of superoxide anions and the release of elastase by human neutrophils with IC50 values of 14.98 and 9.96μM, respectively. Graphical abstract image
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Cyclopropanation of 1,2-dibromoethylphosphonate: a synthesis of β-aminocyclopropylphosphonic acid and derivatives ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Nicolas Rabasso , Antoine Fadel Diethyl (1,2-dibromoethyl)phosphonate was found to undergo cyclopropanation with nitromethane in good yield. The resulting trans β-nitrocyclopropylphosphonate was converted to the trans N-protected aminocyclopropylphosphonate through a reduction–protection sequence. Subsequent hydrolysis gave the free β-aminocyclopropylphosphonic acid without any formation of ring-opening byproduct. Cyclopropanation of 1,2-dibromoethylphosphonates with nitroalkanes and their reduction are also discussed. Graphical abstract image
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[bmIm]OH: an efficient basic catalyst for the synthesis of 4H-benzo[d][1,3-]oxazin-4-one derivatives in solvent-free conditions ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Malik Abdul Waseem , Shireen , Anjali Srivastava , Arjita Srivastava , Rahila , I.R. Siddiqui Reusable [bmIm]OH was found to be a highly efficient renewable homogenous catalyst for the rapid and convenient synthesis of benzoxazine-4-one derivatives from o-iodobenzoic-acid and benzonitrile at 75°C in moderate to good yields. This methodology provides a facile and straightforward path to construct other related heterocycles in an eco-compatible fashion. Graphical abstract image
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Toward the total synthesis of tetrodotoxin: stereoselective construction of the 7-oxanorbornane intermediate ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Atsushi Manabe , Yasufumi Ohfune , Tetsuro Shinada The stereoselective synthesis of 7-oxanorbornane regarding as a key synthetic intermediate of tetrodotoxin (TTX) is reported. The bicyclo ring bearing various functional groups was successfully elaborated by a furan Diels–Alder (DA) reaction. The stereoselective installation of a quaternary amino carbon center to the DA product was achieved with the Tsuji–Trost allylation. The stereochemistry was unambiguously confirmed with X-ray. Graphical abstract image
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Au(I)/Ag(I)-catalyzed annulation of sugar aldehyde tethered with 3-phenylprop-2-yn-1-yl ether with aryl amines for the pyrano[4,3-b]quinoline derivatives ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): B.V. Subba Reddy , Nilanjan Majumder , B. Sridhar Aryl amines undergo smooth annulation with O-phenylpropynyl sugar aldehyde in the presence of the Ph3PAuCl (10mol%)/AgSbF6 (10mol%) catalytic system to afford the corresponding tetrahydro-3aH-spiro[[1,3]dioxolo[4″,5″:4′,5′]furo[3′,2′:5,6]pyrano[4,3-b]quinoline-2,1′-cyclohexane] derivatives in good yields and selectivity. Graphical abstract image
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Highly diastereoselective generation of various 3,3-disubstituted allyl boronates for the stereospecific construction of quaternary centers ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Robyn Aryn Biggs , Maria Lambadaris , William W. Ogilvie Single isomer trisubstituted olefins were converted into allyl boron nucleophiles that were condensed with aldehydes to give products containing quaternary centers. The products were obtained in extremely high diastereomeric ratios, a reflection of the stereochemical integrity of the starting materials. Graphical abstract image
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Isolation and characterization of luminescent bicyclic boronates based on furan ring-opening reactions from 5-formyl-2-furanboronic acid ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Victoria E. González , Felipe Medrano , Mario Rodríguez , Pascal G. Lacroix , Victor Barba A new family of luminescent boronates was prepared from reaction of 5-formyl-2-furanboronic acid with 2-aminophenol derivatives. The furan ring-opening was favored by the presence of the boronic acid group. Evaluation of the photophysical characteristics for all compounds showed significant solvatochromic, fluorescent, and NLO properties. Graphical abstract image
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Colletotrichumine A, a novel indole–pyrazine alkaloid with an unprecedented C16N3-type skeleton from cultures of Colletotrichum capsici ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Zhengxi Hu , Jianping Wang , Xiaobin Bi , Jinwen Zhang , Yongbo Xue , Yingda Yang , Zengwei Luo , Guangmin Yao , Yonghui Zhang Chemical investigations on the EtOAc extract of the cultures of Colletotrichum capsici afforded a novel indole–pyrazine alkaloid embodying a structurally unique C16N3-type skeleton, colletotrichumine A (1), together with five known steroids (2–6). Their structures were elucidated by spectroscopic analysis and that of 1 was further confirmed by a single-crystal X-ray diffraction method. The plausible biogenetic pathway of 1 was also discussed. Graphical abstract image
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Cobalt-catalyzed direct C–C bond formation between tetrahydrofuran and alkynes ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Li Chen , Jiajia Yang , Lin Li , Zhiqiang Weng , Qiang Kang We aimed to describe an efficient CoCl2-catalyzed direct C–C bond formation of tetrahydrofuran (THF) with various alkynes in the presence of tert-butyl hydroperoxide and catalytic amount of acid to obtain vinyl-substituted THFs. Mono- and di-substituted alkynes were suitable for this transformation. Graphical abstract image
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Fluevirines A–D, four new securinega-type alkaloids from Flueggea virosa ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Xiao-Hui Li , Ming-Ming Cao , Yu Zhang , Shun-Lin Li , Ying-Tong Di , Xiao-Jiang Hao Four new securinega-type alkaloids, fluevirines A–D (1–4), along with ten known ones, were isolated from the twigs and leaves of Flueggea virosa. The structures of the new ones were elucidated by means of spectroscopic methods, and their absolute configurations were assigned by CD spectra. Among them, fluevirine A (1) was a novel C,C-linked dimeric indolizidine alkaloid and showed weak antimicrobial activity against Staphylococcus aureus. Graphical abstract image
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Novel one-pot asymmetric cascade approach toward densely substituted enantioenriched α-methylene-γ-lactams ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Yu Tan , Xiao-Di Yang , Wen-Jie Liu , Xing-Wen Sun A novel one-pot asymmetric synthesis of densely substituted α-methylene-γ-lactams in favor of cis-isomer involving Zn-promoted aza-Barbier-type reaction has been well established. A wide array of α-methylene-γ-lactams were obtained in high yields with excellent diastereomeric ratios from 98:2 to >99:1 and good enantioselectivities. The synthetic potential of such α-methylene-γ-lactams was demonstrated by successfully oxidizing the phenol moiety to quinone in quantitative yield. Graphical abstract image
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Total synthesis of proposed structure of coibamide A, a highly N- and O-methylated cytotoxic marine cyclodepsipeptide ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Wei He , Hai-Bo Qiu , Yi-Jie Chen , Jie Xi , Zhu-Jun Yao Total synthesis of the originally proposed structure of coibamide A, a highly N- and O-methylated cytotoxic marine cyclodepsipeptide, has been accomplished by using a [(4+1)+3+3]-peptide fragment-coupling strategy and careful examination and optimization of the multiple dense N-methylated amide-bond formations. The synthetic sample of the proposed coibamide A could not match the natural product in both 1H and 13C NMR spectra, but was found to exhibit low micromolar cytotoxicity against the proliferation of three tested cancer cells. Graphical abstract image
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Rhenium complex-catalyzed coupling reaction of enol acetates with alcohols ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Rui Umeda , Yuuki Takahashi , Yutaka Nishiyama The reaction of enol acetates with alcohols in the presence of a catalytic amount of a rhenium complex, such as ReBr(CO)5, produced the corresponding ketones and aldehydes in moderate to good yields. It was suggested that the preparation of an ether, an intermolecular dehydrated product, was the first step of the reaction. Graphical abstract image
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Synthesis of cinchonidinium salts containing sulfonamide functionalities and their catalytic activity in asymmetric alkylation reactions ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Shinichi Itsuno , Shunya Yamamoto , Shohei Takata Various kinds of 4-(bromomethyl)benzenesulfonamides were prepared as quaternization reagent of cinchonidine. Cinchonidinium salts obtained from the quaternization of cinchonidine with 4-(bromomethyl)benzenesulfonamide showed highly enantioselective catalytic activity in the asymmetric benzylation of N-(diphenylmethylene)glycine tert-butyl ester. The corresponding phenylalanine derivative was obtained in high yield with a high level of enantioselectivity, up to 98% ee. Graphical abstract image
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A one-pot synthesis of 4-aryl-2-methyl-1,2,3,4-tetrahydro-γ-carbolines from 5-aryloxazolidines and indoles via a Mannich/Friedel–Crafts sequence ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Vladimir S. Moshkin , Vyacheslav Y. Sosnovskikh Benzaldehydes react smoothly with the nonstabilized azomethine ylide derived from sarcosine and formaldehyde to form 5-aryloxazolidines, which undergo ring-opening to give 2-(indol-3-ylmethylamino)-1-arylethanols in 69–79% yields on reaction with indoles in acetic acid. Their subsequent acid-catalyzed cyclization into 4-aryl-2-methyl-1,2,3,4-tetrahydro-γ-carbolines was performed in polyphosphoric acid in moderate yields. The latter can also be prepared directly from 5-aryloxazolidines and indoles in polyphosphoric acid. Graphical abstract image
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Smiles rearrangements in a series of berberine analogues containing a secondary acetamide fragment ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Ivan V. Nechepurenko , Nina I. Komarova , Andrey V. Shernyukov , Vladimir G. Vasiliev , Nariman F. Salakhutdinov Smiles rearrangements occurring in the derivatives of the isoquinoline alkaloid, berberine, containing an oxyacetic acid fragment at C-9 are described. Methyl-2-(9-demethoxyberberinebromide-9-yl)oxyacetate reacts with an excess of propylamine followed by sequential aminolysis and Smiles rearrangement leading to 2-hydroxy-N-(berbero-9-yl)-N-propylacetamide in 80% yield. Reactions of berberrubine with secondary amides of bromoacetic acid via Smiles rearrangement give N-substituted 2-hydroxy-N-(berbero-9-yl)acetamides (yields 20–36%). In some cases, the intermediate secondary amides were isolated. Graphical abstract image
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Synthesis of several novel 14-membered ketolides bearing modified 5-O-4′-[1,2,3] triazol desosamine side chain ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Xiaozhuo Chen , Yanpeng Xu , Zhehui Zhao , Pingsheng Lei 4-Azido modified desosamine 4a was synthesized and coupled to erythronolide 9. Using trichloroacetimidate donor in the presence of TMSOTf was considered as the most efficient condition for the glycosylation reaction. Five novel 14-membered ketolides 12a–e bearing modified 5-O-4′-[1,2,3] triazol desosamine side chain were synthesized by the azide/alkyne click chemistry method. Graphical abstract image
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1,8-Naphthalimide-based colorimetric and fluorescent sensor for recognition of GMP, TMP, and UMP and its application in in vivo imaging ()
Publication date: 29 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 44 Author(s): Li Mei Zhang , Lin E. Guo , Xue Mei Li , Yong Gang Shi , Gao Fen Wu , Xiao Guang Xie , Ying Zhou , Qi Hua Zhao , Jun Feng Zhang In this study, a series of 1,8-naphthalimide-based analogs were developed for fluorescence imaging of nucleotides in Caenorhabditis elegans. In DMSO, compound 1 proved to be an effective and selective colorimetric and fluorescent sensor for recognition of GMP, TMP, and UMP over other structurally similar nucleotides. Among all the tested nucleotides, only the addition of GMP, TMP, and UMP resulted in a fluorescence color change from blue to brown with a fluorescence enhancement of more than 600-fold, with the colorless solution turning brown. NMR spectroscopic titration, theoretical calculations, and spectral tests performed using various solvent compositions confirmed that compound 1 formed multiple hydrogen bonds with the related base groups in the nucleotide. Compound 1 demonstrated its utility as a fluorescent chemosensor for detecting GMP, TMP, and UMP in in vivo imaging of GMP, TMP, and UMP in C. elegans. Graphical abstract image
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Editorial board ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43
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Graphical Contents List ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43
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Catalytic CC bond forming transformations via direct β-CH functionalization of carbonyl compounds ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Zhongxing Huang , Guangbin Dong Strategies have emerged over the past decade to enable the direct functionalization of the remote and inert β-CH bonds of carbonyl compounds. Based on these strategies, a wide collection of novel β-CC bond formation transformations have been developed, including arylation, alkylation, alkenylation, alkynylation, and carbonylation. This review summarizes these recent methods for CC bond formations via direct β-CH functionalization of carbonyl compounds. The scope and limitation of each strategy are also discussed. Graphical abstract image
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Direct conversion of epoxides into aziridines with N-arylphosphoramidates ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Fabrizio Minicone , Wendy J. Rogers , James F.J. Green , Mommna Khan , Geoffrey M.T. Smith , Christopher D. Bray Treatment of terminal epoxides with N-arylphosphoramidate anions leads directly to N-aryl aziridines. Existing methods for this transformation employ either multi-step syntheses or an iminophosphorane in conjunction with a Lewis acid. The described method therefore presents an advantage in terms of brevity and atom economy. Graphical abstract image
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A facile method for the synthesis of novel imidoyl iminosulfuranes from imidoyl azides ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Fahimeh Movahedifar , Ali Reza Modarresi-Alam , Behzad Hosseinzadeh A novel and environmentally friendly method for the one-pot preparation of new imidoyl iminosulfuranes in high yield under microwave (MW) and solvent-free conditions from the corresponding imidoyl azides is presented. This efficient synthetic approach benefits from non-toxic and non-explosive precursors for the synthesis of imidoyl iminosulfuranes. Graphical abstract image
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Tocopherol side chain synthesis via asymmetric organocatalytic transfer hydrogenation and convenient measurement of stereoselectivity ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Hyunji Lee , You-Kyoung Lee , Dong-Guk Kim , Mi-Sun Son , Tae-gyu Nam , Byeong-Seon Jeong An asymmetric synthetic route for 1-iodofarnesane, a key intermediate for tocopherol side chain synthesis, starting from (+)-(R)-citronellal was developed. 1-Iodofarnesane was prepared through eight steps in about 50% overall yield, and asymmetric transfer hydrogenation of the enal with a chiral organocatalyst was conducted as a stereoinduction step. To measure the stereoinduction level and optical purity of the product, a convenient analytical method was developed in which a phenylcarbamate derivative of the C15 alcohol was found to be suitable to give proper polarity and UV-activity for chiral UV-HPLC analysis. Graphical abstract image
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New benzotriazole-based reagents for the phosphonylation of various N-, O-, and S-nucleophiles ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Deepak S. Panmand , Anand D. Tiwari , Siva S. Panda , Jean-Christophe M. Monbaliu , Lucas K. Beagle , Abdullah M. Asiri , Christian V. Stevens , Peter J. Steel , C. Dennis Hall , Alan R. Katritzky Benzotriazole surrogates showing higher stabilities than the corresponding chlorophosphates, allow phosphonylation of a variety of N-, O-, and S-nucleophiles in good yields. Graphical abstract image
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Isolation and synthesis of N-acyladenine and adenosine alkaloids from a southern Australian marine sponge, Phoriospongia sp. ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Michelle Farrugia , Nicholas Trotter , Soumini Vijayasarathy , Angela A. Salim , Zeinab G. Khalil , Ernest Lacey , Robert J. Capon Chemical fractionation of the southern Australian marine sponge Phoriospongia sp. (CMB-03107) yielded phorioadenine A (1) as a nematocidal agent and the first reported example of a 6-N-acyladenine natural product. The structure of 1 was confirmed by spectroscopic analysis and the chemical synthesis of racemic (1a) and enantiomeric (1b) analogues. HPLC–ESIMS analysis of the crude sponge extract with comparisons to the synthetic 6-N-acyladenosine 2a provided evidence that the biosynthetically related adenosine, phorioadenosine A (2), was present as a trace co-metabolite. The rare starfish metabolite asterubine (3) was also isolated as a co-metabolite, and its structure confirmed by spectroscopic analysis and chemical synthesis. Biological investigations confirmed that natural products 1–3 and synthetic analogues 1a–e and 2a were not cytotoxic to multiple mammalian cancer cell lines, or Gram-positive or -negative bacteria. Nematocidal activity (inhibition of larval development of Haemonchus contortus) detected in the Phoriospongia sp. extract was attributed to 1 (LD99 31μg/mL), with preliminary structure–activity relationship investigations confirming the importance of the N-acyl side chain. Graphical abstract image
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Efficient and mild method for preparation of allylic amines from aziridine-2-alcohols using PPh3/I2/imidazole ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Subhash P. Chavan , Lalit B. Khairnar , Prakash N. Chavan Allylic amines are synthesized in good to excellent yields by treatment of aziridine-2-alcohols with PPh3/I2/imidazole in THF as solvent under mild conditions. Graphical abstract image
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Operationally convenient method for preparation of sulfonamides containing α,α-difluoro-β-amino carbonyl moiety ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Chen Xie , Lingmin Wu , Haibo Mei , Vadim A. Soloshonok , Jianlin Han , Yi Pan We report here that the reactions of in situ generated unprotected α,α-difluoroenolates with various N-sulfonyl imines take place under operationally convenient conditions affording a novel type of fluorinated sulfonamides of high pharmaceutical potential. The reactions feature structural generality, excellent yields and can be easily scaled up for practical preparation of the target fluorine-containing sulfonamides. Graphical abstract image
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Fungi mediated production and practical purification of (R)-(−)-3-quinuclidinol ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Swati P. Kolet , Dipesh D. Jadhav , Balaraman Priyadarshini , Bhagyashree N. Swarge , Hirekodathakallu V. Thulasiram A fungal system belonging to Mucoraceae family (Mucor piriformis) was explored for the asymmetric reduction of a prochiral ketone, 3-quinuclidinone (I) in an efficient manner to produce an important pharmaceutical precursor (R)-(−)-3-quinuclidinol (II) with ∼96% enantiomeric excess. The efficiency of the process was improved by developing a cation exchange resin (Amberlite IR-120) which assisted the purification of water soluble metabolite II from fermentation media. Graphical abstract image
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A highly efficient synthesis of imidazo-fused polyheterocycles via Groebke–Blackburn–Bienaymè reaction catalyzed by LaCl3·7H2O ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Anand H. Shinde , Malipatel Srilaxmi , Bishnupada Satpathi , Duddu S. Sharada A highly efficient and mild protocol for the synthesis of imidazo-fused polyheterocycles via Groebke–Blackburn–Bienaymè reaction under the influence of catalytic amount of lanthanum chloride heptahydrate has been described. A wide range of nitrogen-enriched polyheterocycles are synthesized with high yields under neat conditions. Graphical abstract image
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Total synthesis of AI-77-B ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Maddimsetti Venkateswara Rao , Batchu Venkateswara Rao , Bokka Ramesh A new stereoselective approach for the synthesis of AI-77-B has been described. Dihydroisocoumarin fragment was made in two routes using Heck reaction followed by oxidation of the olefin and LDA mediated reaction. The chiral amino acid moiety has been obtained from d-ribose involving Grignard reaction on ribosylimine. Finally, condensation of dihydroisocoumarin with acid fragment furnished the title target AI-77-B. Graphical abstract image
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Head group specificity of novel functionalized surfactants: synthesis, self-assembly and calcium tolerance ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Deboleena Sarkar , Ravi Kant Shukla , Vijay Gadgil , Amitava Pramanik The present work describes the synthesis, characterization and application of functionalized surfactants derived through simple organic reaction steps. These surfactants have been particularly tailor made to resist hardness due to calcium ions in water. It is unique of its kind because here the surfactants have an analogous hydrophobic chain but differ structurally in the composition of the head groups in terms of the position of attachment of the chain. The effect of this small variability in the head group on the surfactant property, adsorption, self assembly and calcium tolerance behaviour has been studied in detail. This kind of phenol–keto surfactants has not been reported before. It was also found that one of the surfactants was more tolerant towards Ca2+ ion than the other. The individual packing behaviour of the surfactants at the air–water interface has been projected to cause this difference which is very interesting. Graphical abstract image
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Multicomponent reactions in PEG-400: ruthenium-catalyzed synthesis of substituted pyrroles ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Srivari Chandrasekhar , Vidyavathi Patro , Lahu N. Chavan , Rambabu Chegondi , René Grée An efficient and eco-friendly method for the synthesis of substituted pyrroles has been developed via ruthenium-catalyzed multicomponent reaction of ketone, amine, and ethylene glycol in PEG-400 as solvent medium without using any external ligand. The catalytic system and solvent can be recycled with the same, as well as different, ketones with minimum loss of Ru-catalyst activity. Graphical abstract image
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The rearrangement of cyclopropylketone arylhydrazones. Synthesis of tryptamines and tetrahydropyridazines ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Rinat F. Salikov , Aleksandr Yu. Belyy , Yury V. Tomilov The cyclopropyliminium rearrangement of cyclopropylketone arylhydrazones may result in two possible products. The first one forms via cyclopropane ring-opening and ring-closure to give six-membered tetrahydropyridazines. The second is formed via ring-closure resulting in a five-membered ring and subsequent Grandberg rearrangement into a tryptamine. The product ratio depends on the nature of the starting hydrazones. Graphical abstract image
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Rapid and convenient semi-automated microwave-assisted solid-phase synthesis of arylopeptoids ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Jakob Ewald Rasmussen , Marcello Massimo Boccia , John Nielsen , Claude Taillefumier , Sophie Faure , Thomas Hjelmgaard A facile and expedient route to the synthesis of arylopeptoid oligomers (N-alkylated aminomethyl benz-amides) using semi-automated microwave-assisted solid-phase synthesis is presented. The synthesis was optimized for the incorporation of side chains derived from sterically hindered or unreactive amines and both ortho- and para-substituted arylo-backbones. By utilizing this optimized protocol a complex nonameric arylopeptoid was synthesized in less than 11h, featuring a novel alternating ortho-, meta-, and para-substituted backbone pattern and a variety of chemically diverse and challenging side chains. Graphical abstract image
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Synthesis of substituted quinoline via copper-catalyzed one-pot cascade reactions of 2-bromobenzaldehydes with aryl methyl ketones and aqueous ammonia ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Bin Li , Chenhao Guo , Xuesen Fan , Ju Zhang , Xinying Zhang In this Letter, a new version of the Friedländer synthesis of quinoline derivatives starting from 2-bromobenzaldehydes, aryl methyl ketones, and aqueous ammonia with copper-catalyzed amination as a key step is presented. Remarkable advantages of this new quinoline synthesis include commercially available and economical starting materials, simple operational process, and excellent efficiency. Graphical abstract image
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Two novel polycyclic spiro lignans from Gymnotheca involucrata ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Shi-Ji Xiao , Xin-Xiang Lei , Bing Xia , Dan-Qing Xu , Hong-Ping Xiao , Hong-Xi Xu , Fang Chen , Li-Sheng Ding , Yan Zhou Two novel lignans, gymnothespirolignans A (1) and B (2), possessing a rare polycyclic spiro skeleton, were isolated from the endemic plant of Gymnotheca involucrata Pei. Their structures were determined by spectroscopic evidences and the absolute configurations were confirmed by single crystal X-ray diffraction analysis. Compounds 1 and 2 showed promising antiviral activities against RSV with an IC50 value of 31.87 and 17.51μM, respectively. Graphical abstract image
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Total synthesis of catenioblin B ()
Publication date: 22 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 43 Author(s): Theegala Srinivas , Helmut M. Hügel , Palakodety Radha Krishna Herein we report the first total synthesis of catenioblin B (1) via a titanium(IV) mediated regioselective epoxide ring-opening, Grignard reaction, Luche’s reduction and TEMPO/BAIB mediated intramolecular cyclization as the key steps. Graphical abstract image
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