Reaction of ergosteryl acetate with maleic anhydride and preparation of 5,7-ergostadien-3beta-ol1,2

An improved, large scale synthesis of the ergosteryl acetate-maleic anhydride Diels-Alder adduct and its pyrolysis are described. The complex mixture obtained by reaction of the two constituents was refluxed with methanol to convert the succinic anhydride derivatives, formed by the "ene" reaction, to soluble half esters, leaving the insoluble Diels-Alder adduct largely unchanged. The latter was hydrogenated and pyrolyzed in vacuo to yield 5,7-ergostadienyl acetate together with lesser quantities of the acetates of 7,9(11)-ergostadien-3beta-ol, 6,8(9)-ergostadien-3beta-ol, and 8,14-ergostadien-3beta-ol. These components were separated and purified by argentation column chromatography and crystallization.