Prostaglandin analogues

Prostaglandin analogues of the general formula: II (wherein R1 represents a hydrogen atom or a straight- or branched-chain alkyl group, Y1 represents a carbonyl or hydroxymethylene group, represents a single or double bond, A1 represents an alkylene linkage containing 2 or 3 carbon atoms and optionally bearing a methyl or ethyl substituent, R2 represents a hydrogen atom or a methyl or ethyl group and R3 represents a hydrogen atom or else R2 and R3 form an alkylene linkage containing 2 or 3 carbon atoms, optionally bearing a methyl or ethyl substituent, such that the symbols A1, R2 and R3, together with the carbon atoms through which they are connected, form a cycloalkyl ring of 6, 7 or 8 carbon atoms, optionally bearing one or two methyl or ethyl substituents, X1 represents an ethylene or trans-vinylene group, Y2 represents a carbonyl or hydroxymethylene group, and either (i) A2 represents a straight- or branched-alkylene chain containing from 1 to 3 carbon atoms, Z1 represents a direct bond or an oxygen or sulphur atom, and R4 represents a straight- or branched-chain alkyl group containing from 1 to 12 carbon atoms, optionally substituted by a cycloalkyl group containing from 3 to 8 carbon atoms, or represents a cycloalkyl group containing from 3 to 8 carbon atoms, or represents a phenyl group optionally substituted by a halogen atom or by a trifluoromethyl group or by a straight- or branched-chain alkyl or alkoxy group containing from 1 to 6 carbon atoms, or (ii) A2 and Z1 both represent direct bonds and R4 represents a straight- or branched-chain alkyl group containing from 1 to 12 carbon atoms, optionally substituted by a cycloalkyl group containing from 3 to 8 carbon atoms, or represents a cycloalkyl group containing from 3 to 8 carbon atoms) and cyclodextrin clathrates thereof and, when R1 represents a hydrogen atom, non-toxic salts thereof, possess useful pharmacological properties.