Homochiral 4-hydroxy-5-hexenoic acids and their derivatives and homologues from carbohydrates
摘要:
Efficient routes to chiral 4-hydroxy-5-hexenoic acids and lactones from D-gluconic acid-delta -lactone and L-mannonic acid-gamma -lactone are described. In this approach, the starting lactones are converted to 2,6-dibromo compounds that readily undergo zinc mediated elimination to generate the terminal alkene group in concert with 2-deoxygenation. The integrity of the remaining stereocenters is preserved during the reaction. The related important pharmaceutical intermediates (S)-3-hydroxy-4-pentenoic acid and (S)-1.3-dihydroxy-4-pentene were also prepared from 2-deoxyribose via the corresponding aldonolactone. (C) 2001 Elsevier Science Ltd. All rights reserved.
groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive
Pinnatoxins 属于一类新兴的环亚胺类强海洋毒素。由于无法从天然来源获得复杂的天然产物,因此对其生物学效应的详细研究受到阻碍。这项工作描述了一个强大的、可扩展的合成序列的开发,该序列依赖于聚合策略,该策略为详细的生物学研究提供了足够数量的毒素,并将其商业化以供其他研究小组和监管机构使用。合成中的一个中心转化是复杂的 α,α-二取代烯丙基酯的高度非对映选择性爱尔兰 - 克莱森重排,基于一种独特的立体选择性烯醇化模式,通过底物和氨基锂碱之间的手性匹配。与合成羽扇豆毒素 A,已经进行了一项详细的研究,为其作为对人神经元 α7 亚型具有选择性的烟碱型乙酰胆碱受体的强效抑制剂的作用模式提供了确凿的证据。综合电生理学、生物化学和计算研究支持这样的观点,即羽状毒素的螺亚胺亚基对于阻断烟碱型乙酰胆碱受体亚型至关重要,分析含有开放形式亚胺环的羽状毒素 A 的合成类似物的效果就证明了这一点。我们的研究
γ-lactones from δ-lactones: total synthesis of the biosynthetic derailment product mupirocin H
作者:Robert W. Scott、Carlo Mazzetti、Thomas J. Simpson、Christine L. Willis
DOI:10.1039/c2cc17721h
日期:——
Two different strategies for the synthesis of functionalised γ-lactones from δ-lactones are described and used in a convergent synthesis of (+)-mupirocin H. The total synthesis is versatile and may be readily adapted for the preparation of further truncated metabolites from Pseudomonas fluorescens.
Allylboronates are highly attractive reagents for allyl additions. Enantiomericallypure, stable reagents with a stereogenic centre in alpha-position to boron are especially versatile, albeit often difficult to synthesize. Starting from boron-containing allyl alcohols 6 and 7, which are discussed in detail herein, a set of reagents were obtained via [3,3]-sigmatropic rearrangements and consecutive
Modular Construction of Protected 1,2/1,3-Diols, -Amino Alcohols, and -Diamines via Catalytic Asymmetric Dehydrative Allylation: An Application to Synthesis of Sphingosine
A new enantioselective catalysis has been developed for the one-step construction of methylene-bridged chiral modules of 1,2- and 1,3-OH and/or NH function(s) from δ- or λ-OH/NHBoc-substituted allylicalcohols and “H2C═O”/“H2C═NBoc”. A protonic nucleophile, either in situ-generated CH2OH or CH2NHBoc, is intramolecularly allylated to furnish eight possible 1,2- or 1,3-O,O, -O,N, -N,O, and -N,N chiral
The first example of the use of ionic liquids as reaction media in an asymmetric Pd(II)-catalysed oxycarbonylation was investigated. Based on a ligand screening, the chiral box-type ligands were successfully used in the Pd(II)-promoted bicyclisation of pent-4-ene-1,3 diol (±)-1. The kinetic resolution of (±)-1 in the presence of a chiral catalyst, p-benzoquinone and acetic acid in ionic liquids under a carbon monoxide atmosphere afforded enantioenriched 2,6-dioxabicyclo[3.3.0]octane-3-ones (S,S)-2 (80% ee) and (R,R)-2 (57% ee).