Patent ID: 8003791

Claim:
A compound having the formula: or a pharmaceutically acceptable salt thereof; wherein: P is hydrogen or an amino-group-protecting moiety; X 2 is —C(O)—NH—; R is hydrogen or alkyl, or R forms together with the adjacent R 2 , a nitrogen-containing mono-, bi-, or tri-cyclic, saturated or partially saturated ring system having 4-14 ring members, than can be optionally substituted by one or two of keto, hydroxyl, aryl, alkoxy or aryloxy; R 2 is naphthylmethyl, pyridylmethyl, or quinolinylmethyl; R 3 is one of hydrogen, alkyl, cycloalkyl, aryl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle, or —CH 2 —R 5 , where the ring portion of any of said aryl, aralkyl, alkaryl or heterocycle can be optionally substituted; R 5 , in each instance, is one of aryl, aralkyl, cycloalkyl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle, or —W—R 6 , where W is a chalcogen and R 6 is alkyl, where the ring portion of any of said aryl, aralkyl, or heterocycle can be optionally substituted; Z 1 and Z 2 are independently one of alkyl, hydroxy, alkoxy, or aryloxy, or together Z 1 and Z 2 form a moiety derived from a dihydroxy compound having at least two hydroxyl groups separated by at least two connecting atoms in a chain or ring, said chain or ring comprising carbon atoms, and optionally, a heteroatom or heteroatoms which can be N, S, or O; and A is 0.