Bufadienolides. Part XXIII. 14,15β-epoxy-3β,11α-dihydroxy-5β-bufa-20,22-dienolide (11α-hydroxyresibufogenin)

Abstract

Synthetic procedures have been developed for conversion of gamabufotalin (3p,11α,14-trihydroxy-5β-bufa-20,22-dienolide)(1a) into 11α-hydroxyresibufogenin (5a). Selective dehydration of gamabufotalin with hydrochloric acid in methanol gave the 14-ene (2a). Addition of, for example, hyprobromous acid to this olefin (2a) afforded the bromohydrin (4b) which upon treatment with pyridine easily afforded 11α-hydroxyresibufogenin. As part of this study 11α-hydroxybufalone (11α,l4-dihydroxy-3-oxo-5β-bufa-20,22-dienolide)(3a) was also prepared.