Enantioselective Approaches to Aminocyclopentitols: A Total Synthesis of (+)-6-Epitrehazolin and a Formal Total Synthesis of (+)-Trehazolin
摘要:
Potent inhibitors of trehalase, such as trehazolin and its congeners, represent an attractive approach to the design of effective new insect control agents. In this report, enantioselective total syntheses of (-)-6-epitrehazolin and (+)-trehazolin were achieved using the asymmetric heterocycloaddition between [(benzyloxy)methyl]cyclopentadiene and the acylnitroso compound arising from in situ oxidation of (S)-mandelohydroxamic acid with tetrabutylammonium periodate. Further function- alization of the resulting 3,4,5-trisubstituted cyclopentene, either involving osmylation or epoxidation of the double bond, efficiently created pentasubstituted cyclopentanes. Introduction of the quaternary carbon in both synthesis targets was achieved via stereoselective osmylation of an intermediate 2,3,4,5-substituted 1-methylenecyclopentane.
Neighboring group effects in the regioselective cyclization of vicinal trans-1,2-bromohydrins to epoxides
摘要:
Bromocyclopentitols and amino (or amido) bromocyclopentitols having a C-Br bond trans to two different vicinal hydroxyl groups show selectivity in base-promoted epoxide formation. The role of adjacent polar substituents in directing bromohydrin cyclization is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.