Anti-Bredt-Like Triterpenoids from Mycelial Cultures of the Edible Mushroom Oudemansiella cf. canarii

Sixteen undescribed triterpene glycosides, oudecanarins A-P (1-16), were isolated from cultures of basidiomycete Oudemansiella cf. canarii TBRC-BCC 85371. Oudecanarins A-G (1-7) contain a bicyclo[4.3.1]decene system bearing the bridgehead double bond as a DE ring of pentacyclic triterpene. The unique carbon skeleton was confirmed by the X-ray crystallographic analysis of oudecanarin B (2). The proposed plausible late-stage biosynthetic pathway for oudecanarin A (1) was supported by chemical conversion experiments.