A compound represented by formula (I); a process for producing a compound (substance F-1490) of formula (I), wherein X represents --O-- and R represents a hydroxyl group, by using a microorganism belonging to the genus Cunninghamella; and a Cunninghamella sp. F-1490 strain (FERM BP-8287) capable of producing the substance F-1490; and an osteoclast differentiation inhibitory agent containing as an active ingredient the compound represented by formula (I): ##STR00001## wherein X represents --O-- or --CH.sub.2--, and R represents a hydroxyl group when X represents --O--, or a hydrogen atom when X represents --CH.sub.2--.