Patent ID: 7196113

Claim:
A compound of the formula I: wherein: R 1 is selected from the group consisting of: (1) hydrogen, and (2) C 1-6 alkyl; R 2 is selected from the group consisting of: (1) hydrogen, (2) —OH, (3) —NH 2 , (4) —NH(C 1-6 alkyl), and (5) —N(C 1-6 alkyl)(C 1-6 alkyl); R 3 is selected from the group consisting of: (1) hydrogen, and (2) C 1-6 alkyl; R 4 is selected from the group consisting of: (1) hydrogen, and (2) C 1-6 alkyl; and pharmaceutically acceptable salts thereof and individual enantiomers and diastereomers thereof.