Metabolites of bird's nest fungi. Part 9. Diterpenoid metabolites of Cyathusafricanus Brodie

The diterpenoid metabolites produced when the fungus Cyathusafricanus Brodie (Nidulariaceae) is grown in liquid culture have been examined. The known compounds cyathin A3 (1) and allocyathin B3 (2) were isolated along with four new diterpenoids which have been named cyafrin A4, cyafrin B4, allocyafrin B4, and cyafrin A5. The structures of these substances have been determined by chemical and physical methods to be 3a, 10a, 12a, and 15a, respectively. Cyafrin A4 (3a), allocyafrin B4 (12a), and cyafrin A5 (15a) have been correlated with cyathin A3 by chemical transformations. The absolute stereochemistry of cyathin A3 has been confirmed by the exciton chirality method.