Patent ID: 7501526

Claim:
A compound of formula (V): wherein R 1 is heteroaryl, aryl, C 3 -C 8 cycloalkyl, or C 3 -C 8 heterocycloalkyl; R 2 is H or an amino-protecting group; and each of R 4 , R 5 , and R 6 , independently, is H, OR′, halogen, C 1 -C 10 alkyl, C 3 -C 8 cycloalkyl, C 3 -C 8 heterocycloalkyl, heteroaryl, or aryl; in which R′ is H, C 1 -C 10 alkyl, C 3 -C 8 cycloalkyl, C 3 -C 8 heterocycloalkyl, aryl, or heteroaryl; at most two of R 4 , R 5 , and R 6 being H.