Stereodivergent synthesis of 5a-carba-hexopyranoses from carbohydrates via 6-exo-dig radical cyclization: preparation of 5a-carba-β-d-manno-, α-d-allo-, β-l-talo- and α-l-gulopyranose pentaacetates from d-mannose
作者:Ana M. Gómez、Eduardo Moreno、Gerardo O. Danelón、Serafı́n Valverde、J.Cristóbal López
DOI:10.1016/s0957-4166(03)00532-9
日期:2003.10
Four carbasugars. 5a-carba-beta-D-manno-, alpha-D-allo-, beta-L-talo- and alpha-L-gulopyranose pentaacetates, have been prepared in a stereodivergent manner from D-mannose. Alkynyl derivatives of 2,3:4,6-di-O-isopropylidene-D-mannopyranose, which are prepared by homologation at C-1. by reaction with phenyl acetylide, undergo a 6-exo-dig radical cyclization, from a radical located at C-5. to yield a mixture of highly functionalized cyclohexanes. Some of these compounds, after transformation of their exocyclic double bond in a hydroxy function, were correlated with polyhydroxylated cyclohexanes, which were then selectively deoxygenated either at position C-4 or C-5a (carbohydrate numbering) to afford carbasugars of the D- Or L- series. (C) 2003 Elsevier Ltd. All rights reserved.