Epoxysuccinic acid derivatives, their production and use

PCT No. PCT/JP95/01004 Sec. 371 Date Sep. 5, 1995 Sec. 102(e) Date Sep. 5, 1995 PCT Filed May 25, 1995 PCT Pub. No. WO95/32954 PCT Pub. Date Dec. 7, 1994The present invention relates to a compound of the formula: (I) wherein R1 stands for an optionally esterified or amidated carboxyl group, X stands for an optionally substituted divalent hydrocarbon residue, R2 stands for hydrogen or an optionally substituted hydrocarbon residue, R3 stands for an alkyl group which is substituted with a group bonded through O or S(O)n wherein n is 0, 1 or 2, with a proviso that when the partial structural formula: -NH-X-CO- is leucine residue, R3 is not 3-hydroxy-3-methylbutyl group nor 4-hydroxy-3-methylbutyl group, or a salt thereof, which is useful as prophylactic and therapeutic agents of bone diseases and as inhibitory agents of thiol protease.