反应详情

Prednisolone with 20-hydroxy and 20-carboxamide groups are known, e.g., (VI) (20R)-21-(n-propylamino)-11β,17, 20-trihydroxy-3,21-dioxo-1,4-pregnadiene; and (VI) is reacted with an alkyl acetylalkanoate or alkyl formylalkanoate in the presence of catalytic amount of perchloric acid to produce the corresponding 17,20-carboxycyclic acetal pregnane derivatives, e.g., when methyl acetylbutyrate is used the product is (VII) (20R)-21-(n-propylamino)-11β-hydroxy-3,21-dioxo-17,20-(methyl, methoxycarbony-n-propyl)methylenedioxy-1,4-pregnadiene.