To obtain the subject new compound useful for preventing and treating immunological diseases, asthma, osteodystrophia, nerve cell death, hepatopathy, miscarriage, premature delivery, neurosensory diseases such as glaucoma, etc.

A compound of formula I [R1 is OH or the like; X is chlorine or fluorine; R2 is H, a 1-8C (substituted)alkyl or the like; (n) is 0-4; the portion represented by the solid line and the dotted line is a single bond, a double bond or a triple bond], its non-toxic salt or cyclodextrin clathrate compound. For example, (9β, 11α, 16α)-9-chloro-11,16-dihydroxy-17,17-propano-20-norprosta 13E enoic acid methyl ester of formula II. The compound of formula I (for example, R1 is hydroxyl group) is obtained by hydrolyzing the compound of formula I (R1 is a 1-6C alkoxy group) under an alkaline condition.