A CYCLOADDITION APPROACH TO BREYNOLIDE

Abstract A novel approach to the functionalized hydrobenzothiophene subunit of the sesquiterpene breynolide ( 3 ) has been developed. The sequence features the Diels-Alder reaction of the vinyl sulfones 12 and 13 with the Danishefsky diene 9 to give the cycloadducts 14 and 16 as the major products. Reduction of the sulfone moieties of 14 and 16 gave the sulfides 20 and 21 , respectively. Subsequent dipolar cycloaddition of 20 and 21 with a functionalized nitrile oxide gave the corresponding adducts 24 and 25 , which possess functionality suitable for elaboration into breynolide ( 3 ).