To obtain the subject compound having strong bond of prostaglandin E2 receptor to subsidiary type EP4 and useful for prevention and/or treatment of immunologic diseases, etc.

This compound is represented by formula I [R1 is OH, a 1-4C alkoxy, etc.; R2 is H or OH; R3 is a 1-8C alkyl, a 2-8C alkenyl, a 2-8C alkynyl, etc.; symbol of formula H is double bond or single bond], specifically 11α, 15αdihydroxy-9-oxo-3, 7-dithiaprost-13E-ene acid, etc. Furthermore, the compound is obtained by subjecting a compound represented by formula III (R10 is a 1-4C alkyl) to hydrolysis reaction with an esterase, e.g. in a mixed solution of an organic solvent miscible with water with water in the presence (or absence) of a buffer solution at 0-50°C.