A synthesis of herboxidiene

The natural herbicide herboxidiene was constructed from two key fragments u sing a modified Julia olefination based on the benzothiazolyl sulfone activ ator. Key steps in the synthesis of the C1-C10 oxane fragment were (a) a mo dified Julia olefination using a 1-phenyl-1H-tetrazolyl sulfone as-activato r and (b) an intramolecular addition of an alkoxide to an alpha,beta-unsatu rated eater. Key steps in the synthesis of the C11-C19 polyketide fragment were (a) a directed aldol reaction using a camphor-10,2-sultam as auxiliary ; (b) an Ireland-Claisen rearrangement and (c) a hydroxy-directed epoxidati on.