Versicolamide B
-Versicolamide B and -Versicolamide B are spiroindole alkaloids isolated from the fungus Aspergillus that belong to a class of naturally occurring 2,5-diketopiperazines. The versicolamides are structurally complex spiro-cyclized versions of prenylated cyclo derivatives which possess a unique spiro-fusion to a pyrrolidine at the 3-position of the oxindole core together with the bicyclodiazaoctane ring system. While -versicolamide B was isolated from the marine fungus Aspergillus sp. the enantiomer -versicolamide B was isolated from the terrestrial fungi Aspergillus versicolor NRRL.
The total asymmetric syntheses of both enantiomers have been achieved and the implications of their biosynthesis have been investigated.