Bisphosphonic acid derivatives, as bone resorption inhibitors

A bisphosphonic acid derivative of the formula (I) or a pharmaceutically acceptable salt thereof: ame or different, is (i) a hydrogen atom, (ii) a C1-6 alkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group, a C1-6 alkyl-carbonyl group, a C2-6 alkenyl-carbonyl group, a C2-6 alkynyl-carbonyl group R5 and R6, which may be the same or different, is a hydrogen atom, a hydroxyl group, a halogen atom, a cyano group, a carbamoyl group, an aralkyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted amino group, a C1-6 alkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group; each of m and n is 0 or a positive integer, provided that (m+n) is from 2 to 5; and R is a hydrogen atom, a C1-8 alkyl group or a C7-15 aralkyl group.