Patent ID: 8513290

Claim:
A compound of Formula (I) wherein X is S or O; Y is NR or O, wherein R is H, lower alkyl, or lower arylalkyl; Z is S or O; wherein at least one of X and Z is O; R 1 is H, lower alkyl, or lower arylalkyl; R 2 is lower alkyl, isopropyl, n-propyl, cyclopropyl, isobutyl, n-butyl, sec-butyl, or tert-butyl; R 4 is H, (CH 2 ) n COOH, (CH 2 ) n CONHR, (CH 2 ) n CONHOH, (CH 2 ) n SR 3 , SR 5 (wherein R 5 is lower alkyl or lower aryl), wherein n is at least 1, and wherein R 3 is H, octanoyl, acyl, SR, a higher acyl derivative, or or a pharmaceutically acceptable salt, prodrug, or stereoisomer thereof.