Lichens and fungi. Part 17. The synthesis and absolute configuration at C-20 of the (R)- and (S)-epimers of some 29-substituted lupane derivatives and of some 30-norlupan-20-ol derivatives and the crystal tructure of (20R)-3β-acetoxylupan-29-ol.

Abstract

The absolute configurations at C-20 of the (R)- and (S)-aldehydes (10a), (10b), alcohols (11a), (11b), (13a), and (13b) and acids (12a), (12b), (14a), and (14b) derived from 3β-acetoxylup-20(29)-ene (8), via the epoxide (7), have been established by a combination of physical, spectral and X-ray crystallographic procedures, as have the configurations at C-20 of the (R)- and (S)-3β-acetoxy- and 3β-hydroxy-30-norlupan-20-ols (20a), (20b) and (21a), (21b). Anomalies in the literature are identified and rationalized.