Isolation of a new indoxyl alkaloid, Amoenamide B, from NRRL 35600: biosynthetic implications and correction of the structure of Speramide B.

A new prenylated indoxyl alkaloid, Amoenamide B (), was isolated from NRRL 35600 along with Asperochramide A (). Although many prenylated oxyindole alkaloids, containing bicyclo[2.2.2]diazaoctane cores, have been isolated from the fungus of the genera and to date, is the fourth compound with the indoxyl unit containing the cores. During the structure elucidation of , we found that the planar structure matched to that of Speramide A (), isolated from KM007, but the reported structure of was incorrect and turned out to be that of Taichunamide H (), recently isolated from HDN11-84.