The present invention relates to a novel class of compounds mainly,
substituted leucinamide-carboxylate derivatives of formula (I) wherein X
is O or NR.sup.9, Y is CR.sup.1R.sup.2, --SO.sup.2, C.dbd.O or NR.sup.9;
Z is CR.sup.1R.sup.2, O, S, --SO.sup.2 or NR.sup.9 and each G is
independently a CR.sup.1CR.sup.2 and pharmaceutical compositions thereof.
Said compounds are cathepsin cysteine protease inhibitors, including but
not limited to, inhibitors of cathepsin K, L, S and B. These compounds
are useful for treating and preventing cathepsin dependent conditions in
which inhibition of bone resorption is indicated, such as osteoporosis.