A one-pot and highly diastereoselective method for the reductive dehydroxylation of three classes of heterocyclic N,O-acetals with general structure 4 is reported. The method features a 'two in one' concept, namely, by synergetic action of two complementary Lewis acids (BF.OEt2 and TiCl4), the bicyclic or tricyclic oxazololactams 5 were formed in situ and reductively cleaved to give the corresponding lactams 6 in a high-yielding and highly diastereoselective manner. (C) 2009 Elsevier Ltd. All rights reserved.
A Flexible Approach to Methyl
(5<i>S</i>)-5-Alkyltetramate Derivatives
作者:Jian-Feng Zheng、Pei-Qiang Huang、Li-Jiao Jiang、Hong-Qiao Lan、Jian-Liang Ye
DOI:10.1055/s-0028-1087672
日期:——
Regioselective Grignard reagent additions to 3-methoxymaleimides and subsequent diastereoselective reductive dehydroxylation of the resulting N,O-acetals were studied. On the basis of these studies, a flexible and highly regio- and diastereoselective approach to methyl 5-alkyltetramate derivatives was disclosed. The method is the first direct and flexible asymmetric cationic synthon-based approach, and allows for the synthesis of various methyl (5S)-5-alkyltetramate derivatives that are otherwise inaccessible by the commonly used methods based on α-amino acids.