Patent ID: 7192918

Claim:
A compound of the formula or its C 1-10 alkyl, phenyl-C 1-3 alkyl, or (C 5-6 heteroaryl)-C 1-3 alkyl mono- or di-ester; or a salt of the compound or its mono- or di-ester, where: X is L -γ-glutamyl or L -γ-glutamylglycyl; Y is H, optionally substituted alkyl, optionally substituted heteroalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, or optionally substituted heteroaralkyl; and Z is C 5-9 alkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, or optionally substituted heteroaralkyl.