Aldol Reactions between L-Erythrulose Derivatives and Chiral α-Amino and α-Fluoro Aldehydes: Competition between Felkin-Anh and Cornforth Transition States
作者:Santiago Díaz-Oltra、Miguel Carda、Juan Murga、Eva Falomir、J. Alberto Marco
DOI:10.1002/chem.200800956
日期:2008.10.20
Both matched and mismatched diastereoselection have been observed in aldolreactions of a boronenolate of a protected L-erythrulose derivative with several chiral alpha-fluoro and alpha-amino aldehydes. Strict adherence to the Felkin-Anh model for the respective transitionstructures does not account satisfactorily for all the observed results, as previously observed in the case of alpha-oxygenated
Synthesis of a C1C14 subunit of the macrodiolide antibiotics pamamycin-607 and pamamycin-635B
作者:Robert D. Walkup、Young Soo Kim
DOI:10.1016/0040-4039(95)00471-n
日期:1995.5
A nonracemic C1C14 portion of the antibiotics pamamycin-607 and -635B was prepared using a route which features two stereoselective aldol reactions (including an apparent kinetic resolution via the Evans aldol reaction), a stereospecific intramolecular oxymercuration of a γ-silyloxyallene, a stereospecific conjugate reduction of a β-alkoxy-α-methylene carboxylate ester, and use of the 2,6-di--butyl-4-methoxyphenyl
Enantioselective monoreduction of 2-alkyl 1,3-diketones using chiral ruthenium catalysts. Synthesis of the C14C25 fragment of bafilomycin A1
作者:Florence Eustache、Peter I. Dalko、Janine Cossy
DOI:10.1016/j.tetlet.2003.09.192
日期:2003.12
The enantioselective monoreduction of 2-alkyl 1,3-diketones by dynamic kinetic resolution using optically active ruthenium catalysts allowed the preparation of the C14–C25 fragment of bafilomycin A1.
The stereochemistry of the addition of titanium enolates of N-propionyl-oxazolidin-2-ones to 5- and 6-membered N-acyliminium ions
作者:Ronaldo A. Pilli、Conceição de Fátima Alves、Maria Alice Böckelmann、Yvonne P. Mascarenhas、J. Geraldo Nery、Ivo Vencato
DOI:10.1016/s0040-4039(99)00398-6
日期:1999.4
The stereochemistry of the addition of the N-propionyl titanium enolates 2a and 2b to 5- and 6-membered 2-ethoxycarbamates 1a-f was investigated. The addition proceeded stereoselectively to afford the corresponding (2S,1′S)-2-substituted pyrrolidines as the major diastereoisomer. Despite the lack of reactivity between 2-ethoxypiperidines 1b and N-propionyl titanium enolates 2a and 2b, less bulky carbamate
A new fluoride ion cleavable linker serves as starter unit for iterative asymmetric aldol reactions on a solid support. The synthetic protocol relies on the baron enolate chemistry of D. A. Evens and a cyclic reestablishment of key functionalities. It entails the opportunity for the generation of di-and triketide libraries. (C) 1998 Elsevier Science Ltd. All rights reserved.