New intermediates for the preparation of 13-thiaprostaglandin derivatives

A process for preparing a compound regiospecifically in the 2.beta.-position, the compound being of the formula ##STR7## wherein A is a C--C single bond, --CH.sub.2, --CH(CH.sub.3)--, --C(CH.sub.3).sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH(CH.sub.3)CH.sub.2 --, --C(CH.sub.3).sub.2 CH.sub.2 --, --CH.sub.2 --CH.sub.2 --CH.sub.2 -- or --CH.sub.2 O--;

• R.sup.1a and R.sup.1 each independently is hydrogen or a protective group which can be cleaved by solvolysis with an acid or a base or by catalytic hydrogenolysis;
• R.sup.2 is H or alkyl of 1 to 3 C atoms;
• R.sup.3 is alkyl of 3 to 5 C atoms, phenyl or phenyl which is monosubstituted to trisubstituted by F, C1, OH, OCH.sub.3, OC.sub.2 H.sub.5, CF.sub.3 or alkyl of 1 to 3 C atoms, or, when A is not --CH.sub.2 O--, can also be pyridyl, thienyl, naphthyl or alkoxy of 1 to 4 C atoms;
• ----indicates a bond in the .alpha.-position, indicates a bond in the .beta.-position and a wavy line means that the bond can be in the .alpha.-or .beta.-position
• comprising reacting, under basic conditions the corresponding 2 .beta.-bromo-3.alpha.-hydroxy-bicyclo [3.2.0]heptan-6-one, with retention of configuration, at the 2- and 3-positions,
• with a thiol or thiolate of the formula ##STR8## wherein M is H, one equivalent of a metal atom or an ammonium ion and A and R.sup.1 to R.sup.3 are as defined above.