6,9-Methano-PGI2 analogues

A prostaglandin I.sub.2 analogue of the formula:

• ##STR50## wherein the symbol between the carbon atoms in positions 5 and 6 represents a single or double bond, Y represents ethylene or trans-vinylene, R.sup.1 represents a hydrogen atom, a straight- or branched-chain alkyl group containing from 1 to 12 carbon atoms, ar aralkyl group containing from 7 to 12 carbon atoms, a cycloalkyl group containing from 4 to 7 carbon atoms unsubstituted or substituted by at least one straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, a phenyl group unsubstituted or substituted by at least one chlorine atom, trifluoromethyl group, alkyl group containing from 1 to 4 carbon atoms or phenyl group, a --C.sub.m H.sub.2m COOR.sup.7 group, wherein m represents an integer of from 1 to 12 and R.sup.7 represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, a --C.sub.n H.sub.2n OR.sup.8 group, wherein n represents an integer of from 2 to 12 and R.sup.8 represents a hydrogen atom or a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms, or a ##STR51## group, wherein R.sup.9 and R.sup.10, which may be the same or different, each represents a straight- or branched-chain alkyl group containing from 1 to 4 carbon atoms and n is as hereinbefore defined, R.sup.2 represents a hydrogen atom or a hydroxy-protecting group which is eliminated under acidic or alkaline conditions selected from the group consisting of tetrahydropyran-2-yl, tetrahydrofuran-2-yl, tetrahydrothiopyran-2-yl, 1-ethoxyethyl, (1-methoxy-1-methyl)ethyl, 1-methoxycyclohexyl, (1-methoxy-1-phenyl)ethyl, trimethylsilyl, triethylsilyl, tri-n-butylsilyl, tert-butyldimethylsilyl, tribenzylsilyl, triphenylsilyl, acetyl, chloroacetyl, dichloroacetyl, trichloroacetyl, trifluoroacetyl, propionyl, benzoyl, p-phenylbenzoyl, and naphthyloyl, R.sup.3 represents a hydrogen atom or a hydroxy-protecting group which is eliminated under acidic conditions selected from the group consisting of tetrahydropyran-2-yl, tetrahydrofuran-2-yl, tetrahydrothiopyran-2-yl, 1-ethoxyethyl, (1-methoxy-1-methyl)ethyl, 1-methoxy-cyclohexyl, (1-methoxy-1-phenyl)ethyl, trimethylsilyl, triethylsilyl, tri-n-butylsilyl, tert-butyldimethylsilyl, tribenzylsilyl, and triphenylsilyl, R.sup.4 represents a hydrogen atom or a methyl or ethyl group, R.sup.6 represents a cycloalkyl group containing from 4 to 7 carbon atoms unsubstituted or substituted by at least one straight- or branched-chain alkyl group containing from 1 to 8 carbon atoms, the wavy line attached to the carbon in position 15 represents .alpha.- or .beta.-configuration or a mixture thereof and when represents a double bond, the double bond between C.sub.5 -C.sub.6 is E, Z or a mixture thereof, and when represents a single bond, the absolute configuration of C.sub.6 is R, S or a mixture thereof and, when R.sup.2 and R.sup.3 represent hydrogen atoms, cyclodextrin clathrates of such acids and esters and, when R.sup.1, R.sup.2 and R.sup.3 represent hydrogen atoms non-toxic salts thereof and, when R.sup.1 represents a ##STR52## group in which n, R.sup.9 and R.sup.10 are as hereinbefore defined, non-toxic acid addition salts thereof.