BICYCLIC LACTONE DERIVATIVES EMPLOYED AS INTERMEDIATES IN THE SYNTHESIS OF PROSTAGLANDINES

The invention 1s concerned with a novel process for producing compounds of formula 1 I wherein R3 and R4 are the same or different and each represent hydrogen or a lower alkanoyl group whlich is unsubstituted or is substituted by one, two or three halogen atoms, or R3 and R4 together form a qroup R5-?-R6 wherelin R5 and R6 are the same or different and each represent hydrogen or a methyl or phenyl group, with the proviso that when one of R5 and R6 is phenyl the other is hydrogen. The compounds of formula I are obtained by reacting a lactone of formula II II with formaldehyde or a polymer of formaldehyde in the procence of a strong acid, followed, if necessary, by reaction with a compound of formula R5COR6 or R5CHO or an acetal thereof. The compounds of formula I are useful lntermediates in Corey's synthesis of prostaglandins and those compounds in which R3 and R4 form a group ,5-?-R are novel.