Rearrangement of 5-trimethylsilylthebaine on treatment with L-selectride: an efficient synthesis of (+)-bractazonine |
| |
Authors: | Chen Weibin Wu Huifang Bernard Denzil Metcalf Matthew D Deschamps Jeffrey R Flippen-Anderson Judith L MacKerell Alexander D Coop Andrew |
| |
Affiliation: | Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 North Pine Street, Baltimore, Maryland 21201, USA. |
| |
Abstract: | Treatment of 5-trimethylsilylthebaine with L-Selectride gave rise to a rearrangement to 10-trimethylsilylbractazonine through migration of the phenyl group, whereas treatment of thebaine with strong Lewis acids is known to lead to a similar rearrangement through migration of the alkyl bridge to give, after reduction, (+)-neodihydrothebaine. It is suggested that the rearrangement of the alkyl group of thebaine is favored due to the formation of a tertiary benzylic cation. However, for 5-trimethylsilylthebaine, the lithium ion of L-Selectride acts as the Lewis acid and the beta-silyl effect dominates in the stabilization of any positive charge. This rearrangement provides a clear example of the greater relative migratory aptitude of phenyl groups over alkyl groups, and provides an efficient synthesis of (+)-bractazonine from thebaine. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|