Process for making bicyclic lactone derivatives for use as intermediates in the synthesis of prostaglandins

A process for the preparation of optically active or racemic lactone diol derivatives of the formula (for use as intermediates in the Corey prostaglandin synthesis). Optically active or racemic lactone diol derivatives are inclosed, in which R3 and R4 are the same or different and stand for a hydrogen, or a lower alkanoyl optionally substituted with one, two or three halogen atoms, or form together a group, in which R5 and R6 are the same or different and stand for a hydrogen, alkyl or aryl, with a process for preparing them. According to the invention the above compound are prepared by reacting optically active or racemic lactone of the formula II with formaldehyde or with a formaldehyde polymerisate, in the presence of the mixture of a strong acid and water or of a lower alkane carboxylic acid optionally substituted with one, two or three halogen atoms, and then optionally subjecting the obtained compound of the general formula I, in which R3 and/or R4 stand for an alkanoyl optionally substituted with one, two or three halogen atoms to partial or total hydrolysis or alcoholysis in an acid or alkaline medium and/or reacting it with the oxo-compounds of the formula R5-CHO or R6-CO-R5 or with the acetals of the above compounds. The compounds according to the invention are useful intermediates in the Corey prostaglandine synthesis.