Application of modular nucleophilic glycine equivalents for truly practical asymmetric synthesis of β-substituted pyroglutamic acids
摘要:
A new series of achiral glycine equivalents have been evaluated with respect to their synthetic utility for the production of beta-substituted pyroglutamic acid derivatives. Among them, the piperidine-de rived complex was found to be a superior glycine derivative for the Michael additions with various (R)-N-(E-enoyl)-4-phenyl-1,3-oxazolidin-2-ones representing a general and practical synthesis of sterically constrained beta-substituted pyroglutamic acids. In particular, application of complex allowed for the first time preparation of the corresponding isopropyl derivatives thus increasing the synthetic efficiency and expanding generality these Michael addition reactions. (C) 2004 Elsevier Ltd. All rights reserved.
A Convenient, Room-Temperature–Organic Base Protocol for Preparing Chiral 3-(Enoyl)-1,3-oxazolidin-2-ones
摘要:
In this study, we developed a new protocol for the preparation of the chiral 3-[(E)-enoyl]-1,3-oxazolidin-2-ones under the ultimately simple reaction conditions starting with the corresponding enoyl chlorides and 1,3-oxazolidin-2-ones with Et3N/LiCl at room temperature. The method generally allows efficient preparation of various derivatives regardless of the steric and electronic nature of the substituents on both the enoyl or the oxazolidinone sites. Excellent yields, combined with the simplicity of the experimental procedures, render the present method immediately useful for preparing the target compounds.