摘要在以前的论文中[A. El Nemr和T. Tsuchiya,四面体Lett。,36(1995)7665-7668;A. El Nemr,T。Tsuchiya和Y. Kobayashi(碳水化合物)。Res。,293(1996)31–59],我们报道了当一些碳水化合物三氟甲磺酸酯用乙醚中的MeLi(或BuLi)处理时,会产生新的反应,生成C-甲基(或丁基)或不饱和化合物。这两个反应都可以通过三氟甲磺酸酯中的α-氢消除来解释。本文是对先前工作的扩展,描述了一些α-d-糖吡喃糖苷的3-或4-三氟甲酸酯的不饱和机理。通过使用氘代类似物,发现2-O-苄基-4,6-O-亚苄基-3-O-三氟甲基-α-d-吡喃葡萄糖苷通过α生成2,3-和3,4-不饱和化合物-氢消除,相应的去甲吡喃糖苷得到2,通过α-和β-(对于14)和α-氢消除(对于19)的3-不饱和化合物。提出将碳的形成作为消除前者的关键中间体
α-Hydrogen elimination in some carbohydrate triflates
作者:Ahmed El Nemr、Tsutomu Tsuchiya
DOI:10.1016/0040-4039(95)01607-j
日期:1995.10
In somecarbohydrate triflates, treatment with MeLi (or BuLi) in ether caused α-hydrogen elimination initially, then the resulting carbanion is stabilized to give either C-methyl(or butyl)-hydroxy derivatives or unsaturated products.
α-hydrogen elimination in some 3- and 4-triflates of α-d-glycopyranosides
作者:Ahmed El Nemr、Tsutomu Tsuchiya
DOI:10.1016/s0008-6215(97)00080-3
日期:1997.6
new reactions that occur when some carbohydrate triflates are treated with MeLi (or BuLi) in ether, giving C -methyl (or butyl) or unsaturated compounds. Both reactions may be explained by α-hydrogen elimination in the triflates. This paper is an extension of the previous work and describes the mechanism of unsaturation of some 3- or 4-triflylates of α- d -glycopyranosides. By using deuterated analogs
摘要在以前的论文中[A. El Nemr和T. Tsuchiya,四面体Lett。,36(1995)7665-7668;A. El Nemr,T。Tsuchiya和Y. Kobayashi(碳水化合物)。Res。,293(1996)31–59],我们报道了当一些碳水化合物三氟甲磺酸酯用乙醚中的MeLi(或BuLi)处理时,会产生新的反应,生成C-甲基(或丁基)或不饱和化合物。这两个反应都可以通过三氟甲磺酸酯中的α-氢消除来解释。本文是对先前工作的扩展,描述了一些α-d-糖吡喃糖苷的3-或4-三氟甲酸酯的不饱和机理。通过使用氘代类似物,发现2-O-苄基-4,6-O-亚苄基-3-O-三氟甲基-α-d-吡喃葡萄糖苷通过α生成2,3-和3,4-不饱和化合物-氢消除,相应的去甲吡喃糖苷得到2,通过α-和β-(对于14)和α-氢消除(对于19)的3-不饱和化合物。提出将碳的形成作为消除前者的关键中间体
A New Reaction for the Direct Conversion of 4-Azido-4-deoxy-<scp>d</scp>-galactoside into a 4-Deoxy-<scp>d</scp>-<i>e</i><i>rythro</i>-hexos-3-ulose
作者:Jie Xue、Jian Wu、Zhongwu Guo
DOI:10.1021/ol0499046
日期:2004.4.1
A new one-step reaction has been developed for converting 4-azido-4-deoxy-D-galactoside into 4-deoxy-D-erythro-hexos-3-ulose by phosphoramidites and tetrazole. It is proposed that the new reaction proceeds via an intramolecular Staudinger reaction of the phosphite A intermediate and a tetrazole-catalyzed elimination reaction of the resultant phosphorimidate. Tetrazole appears to be playing a unique role by acting as a bifunctional catalyst to facilitate the elimination reaction.
An efficient and highly regioselective synthesis of 4-deoxy- and 2-acetamido-2,4-dideoxy-β-d-threo-hex-3-enopyranosides
The preparation of the previously undescribed class of 4-deoxy- and 2,4-dideoxy-2-acetamido-beta-D-threo-hex-3-enopyranosides was accomplished with a very high yield and a complete regioselectivity by means of a simultaneous activation-elimination process of the OH-4 group of beta-D-talopyranosides (5a,b) and 2-acetamido-2-deoxy-beta-D-talopyranosides (5c,d) with NaH/'N,N'-sulfuryldiimidazole. The same reaction of analogous beta-D-galactopyranosides (5e,f) is not regioselective, leading to mixtures of 3- and 4-hexeno derivatives. This difference is evidently determined by the orientation of the C-2 substituent, which, in the talo series, is anti diaxially disposed to the H-3 eliminating group. (C) 2002 Elsevier Science Ltd. All rights reserved.
Reactions of some 2- and 4-O-triflylglycopyranosides with MeLi, t-BuOK, and pyridine
作者:Ahmed El Nemr、Tsutomu Tsuchiya
DOI:10.1016/s0008-6215(00)00291-3
日期:2001.1
Carbohydr. Res. 1997, 301, 77-87. El Nemr, A.; Tsuchiya, T. Carbohydr. Res. 1997, 303, 267-281], the reaction modes of several methyl 2- and 4-O-triflyl-D-glycopyranosides with MeLi (strong base), t-BuOK (moderately strong base), and pyridine (weak base) have been studied. This paper describes the reactions of 3-O-benzyl-4,6-O-benzylidene-2-O-triflyl-D-gluco and -mannopyranosides with MeLi to give mainly