Prostaglandins

A compound of the formula (I)

• represents one of the divalent groups ##STR74## the letters a and b indicating in each case the points of attachment of the substituents R.sup.1 and C(R.sup.2).dbd.NR, respectively:
• wherein
• R.sup.1 is a group of the formula R'--COQ where R' is selected from the group consisting of --(CH.sub.2).sub.j -- where j is an integer from 4 to 8;
• --CH.dbd.CH--(CH.sub.2).sub.k --, where k is 2 or 3;
• --CH.sub.2 --CH.dbd.CH--(CH.sub.2).sub.m --, where m is an integer from 1 to 5;
• --CH.sub.2 --CH.sub.2 --CH.dbd.CH--(CH.sub.2).sub.n --, where n is 0 or an integer from 1 to 4;
• --X--(CH.sub.2).sub.p --, where p is an integer from 3 to 7;
• --CH.sub.2 --X--(CH.sub.2).sub.q --, where q is an integer from 2 to 6;
• and CH.sub.2 --CH.sub.2 --X--(CH.sub.2).sub.m --, where X is O or S;
• and COQ is carboxy, a physiologically acceptable carboxylate salt, a C.sub.1 -C.sub.5 alkyl ester or CONHSO.sub.2 CH.sub.3 ;
• R.sub.2 is selected from the group consisting of hydrogen, C.sub.1-10 aliphatic hydrocarbon groups, and C.sub.1-10 aliphatic hydrocarbon groups substituted by Ar, OAr or SAr, where Ar represents a phenyl, naphthyl, fluorenyl, dibenzocyclohexyl, dibenzocycloheptyl, pyridyl, benzthiazolyl, dihydrobenzthiazolyl, N-methyldihydrobenzthiazolyl, benzoxazolyl, dihydrobenzoxazolyl or N-methydihydrobenzoxazolyl group or such a group substituted by one or more substituents selected from C.sub.1-10 alkoxy, halogen, C.sub.1-10 halogen-substituted alkyl, sulphamoyl, amino, hydroxyl, nitro and C.sub.1-10 alkyl groups;
• and
• R is a group --OR.sup.3, --OR.sup.4, --A--R.sup.3 or --N.dbd.R.sup.5 in which A is --NH--, --NH.CO--, --NH.CO.CH.sub.2 N(R.sup.6)--, --NH.SO.sub.2 --, --NH.CO.NH-- or --NH.CS.NH-- and wherein R.sup.3 is a C.sub.1-10 aliphatic hydrocarbon group, a group Ar or a C.sub.1-10 aliphatic hydrocarbon group substituted by one or more groups selected from Ar, OAr, and SAr;
• R.sup.4 is a C.sub.1-10 aliphatic hydrocarbon group which is substituted through an oxygen atom by a C.sub.1-10 aliphatic hydrocarbon group which is itself substituted by one or more groups Ar;
• R.sup.5 is a C.sub.1-10 aliphatic hydrocarbon group, a group Ar', where Ar' represents a fluorenylidene, dibenzocyclohexylidene, dibenzocycloheptylidene, dihydrobenzthiazolylidene, N-methyldihydrobenzthiazolylidene, dihydrobenzoxazolylidene or N-methyldihydrobenzoxazolylidene group or such a group substituted on a benzene ring or rings thereof by one or more substituents selected from C.sub.1-10 alkoxy, halogen, C.sub.1-10 halogen-substituted alkyl, sulphamoyl, amino, hydroxyl, nitro and C.sub.1-10 alkyl groups, or a C.sub.1-10 aliphatic hydrocarbon group substituted by one or more groups selected from Ar, OAr and SAr;
• an R.sup.6 is hydrogen, a C.sub.1-10 aliphatic hydrocarbon group, a group Ar or a C.sub.1-10 aliphatic hydrocarbon group substituted by one or more groups selected from Ar, POAr and SAr.