Oligomeric flavanoids. Part 1. Novel dimeric profisetinidins from Colophospermum mopane

Abstract

The range of natural dimeric profisetinidins is extended by the recognition of a series of novel (4,6)-coupled analogues based not only on (–)-fisetinidol [(2R,3S)-2,3-trans-flavan-3,3′,4′,7-tetraol] but for the first time also on (+)-epifisetinidol [(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] as constituent units, e.g. the (–)-fisetinidol-(4α,6)- and (4β,6)-(+)-epifisetinidols. They are accompanied by bis(4α,6′)-(–)-fisetinidol and (–)-fisetinidol-(4α,6′)-(+)-epifisetinidol, the first prototypes of naturally occurring B-ring coupled profisetinidins, and by the first dimeric peltogynoid analogue, (2S,3S,4R)-2,3-cis-3,4-trans-4[(2R,3_S)-2,3-trans-3-hydroxy-3′,4′,7-trihydroxyflavan-6-yl]mopanane-3′,4′,7-triol.