4-hydroxy-2-cyclopentenone derivatives and anticancer agent and bone formation accelerator containing the same

A method of accelerating bone formation comprising administering,

• as an effective active ingredient, at least one optically active 4-hydroxy-2-cyclopentenone compound having formula (I):
• ##STR224## wherein Y is a hydrogen atom or a halogen atom;
• A and B are such that B is a hydrogen atom and A is selected from the group consisting of a hydroxyl group, a C.sub.2 -C.sub.7 acyloxyl group, a C.sub.2 -C.sub.5 alkoxycarbonyloxyl group and a C.sub.1 -C.sub.7 sulfonyloxy group or A and B together form a single bond;
• R.sup.2 is substituted or unsubstituted and is selected from the group consisting of (i) a C.sub.4 -C.sub.10 alicyclic hydrocarbon group, (ii) a C.sub.6 -C.sub.10 aromatic hydrocarbon group and (iii) a C.sub.1 -C.sub.9 aromatic heterocyclic group;
• R.sup.3 is substituted or unsubstituted and is selected from the group consisting of (i) a C.sub.1 -C.sub.10 aliphatic hydrocarbon group, (ii) a C.sub.4 -C.sub.10 alicyclic hydrocarbon group and (iii) a C.sub.6 -C.sub.10 aromatic hydrocarbon group;
• R.sub.4 is a hydrogen atom, a C.sub.1 -C.sub.4 alkyl group, a C.sub.2 -C.sub.7 acyl group, a C.sub.2 -C.sub.5 alkoxycarbonyl group, a tri (C.sub.1 -C.sub.7) hydrocarbon silyl group and a group forming an acetal bond together with the oxygen atom to which R.sub.1 is bonded;
• R.sup.5 is substituted or unsubstituted and is selected from the group consisting of (i) a C.sub.1 -C.sub.10 aliphatic hydrocarbon group, (ii) a C.sub.4 -C.sub.10 alicyclic hydrocarbon group and (iii) a hydrogen atom, and mixtures thereof, and
• a pharmaceutically acceptable carrier.