Biomimetic conversion of (−)-fusoxypyridone and (−)-oxysporidinone to (−)-sambutoxin: Further evidence for the structure of the tricyclic pyridone alkaloid, (−)-fusoxypyridone

Abstract

Biomimetic-type reactions of the tricyclic pyridone alkaloid, (-)-fusoxypyridone [(-)-4,6'-anhydrooxysporidinone] (1), recently encountered in an endophytic strain of Fusarium oxysporum, and (-)-oxysporidinone (2) afforded (-)-sambutoxin (3) and an analogue of 1, identified as (-)-1'(6')-dehydro-4,6'-anhydrooxysporidinone (4), thus confirming the structure previously proposed for 1 and suggesting that 1-3 bear the same relative stereochemistry. Oxidation of 4 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yielded a hitherto unknown sambutoxin analogue, (-)-4,2'-anhydrosambutoxin (5).