Cyanohydrin glycosides of passifloraceae

Abstract

Barterin, a classical cyclopentenoid cyanohydrin glucoside, was shown to be (1 S,4 S)-1-(β- d-glucopyranosyloxy)-4-hydroxy-2-cyclopentene-1-carbonitrile, being thus identical with tetraphyllin B, contrary to previous statements in the literature. Cyanohydrin glycosides from Adenia dinklagei, A. epigea, A. firingalavensis, A. frutescens, A. hastata, A. letouzeyi, A. spinosa, Passiflora coriacea, P. subpeltata, P. warmingii and Smeathmannia pubescens were isolated and identified. A summary of the present knowledge of distribution of cyanohydrin glycosides in Passifloraceae shows clear differences between the two chief genera, Adenia and Passiflora. Thus, the former genus appears to be dominated by β- d-glucopyranosides of 2-cyclopenten-1-one and 4-hydroxy-2-cyclopenten-1-one cyanohydrin; the glycosides generally occur as pairs having enantiomeric aglycones and the cyclopentene ring is usually trans-1,4-dioxygenated. By contrast, the pattern of cyanohydrin glycosides of Passiflora appears to be highly diversified, comprising valine or isoleucine-derived glycosides as well as cyclopentenoid glycosides, including more elaborate forms than those found in Adenia. The origin of epilotaustralin, possibly arising from the (3 R)-epimer of l-isoleucine, is briefly discussed.