Oligomeric flavanoids. Part 25. Cleavage of the acetal functionality in A-type proanthocyanidins
作者:Petrus J. Steynberg、Annemarie Cronjé、Jan P. Steynberg、Barend C.B. Bezuidenhoudt、E.Vincent Brandt、Daneel Ferreira
DOI:10.1016/s0040-4020(96)01149-0
日期:1997.2
and A-2 2 are subject to facile cleavage of the acetal functionality with sodium cyanoboranuide in trifluoroacetic acid at 0°C. This straight forward chemical method permits the unambiguous establishment of the absolute configuration of the DEF-flavanyl unit and the D-ring carbon and oxygen atoms that are involved in the double linkage of the A-class proanthocyanidins.
Enantioselective Synthesis of the Four Catechin Diastereomer Derivatives
作者:Hendrik van Rensburg、Pieter S. van Heerden、Barend C.B. Bezuidenhoudt、Daneel Ferreira*
DOI:10.1016/s0040-4039(97)00552-2
日期:1997.4
Asymmetric dihidroxylation of (E)-1-(3,4-dimethoxyphenyl)-3-(2-methoxy-methyl-4,6-dimethoxy-phenyl)-propene with AD-mix-alpha or AD-mix-beta in the presence of methanesulfonamide, followed by acid catalysed cyclization, afforded the four catechin diastereomers in high enantiomeric excesses and yields. (C) 1997 Published by Elsevier Science Ltd.