Patent ID: 8093260

Claim:
A compound of the formula (I): wherein each of R 1 , R 2 , and R3, independently, is hydrogen, C 1-6 alkyl, or —C(O)R 5 ; R 4 is C 1-6 alkyl, or —C(O)R 5 ; R is —C(O)R 5 , or C 1-6 alkyl substituted by a member selected from the group consisting of: (i) —C(O)OR 6 , (ii) —C(O)NR 6 R 7 , (iii) at least two of —OR 6 , (iv) at least one of —NR 6 R 7 , (v) C 4-9 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, and (vi) C 4-9 heterocyclyl containing at least one heteroatom selected from the group consisting of N, O and S; R 5 is C 4-9 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, or C 1-6 alkyl substituted by —NR 6 R 7 or C 4-9 heterocyclyl containing at least one heteroatom selected from the group consisting of N, O and S; each of R 6 and R 7 , independently, is hydrogen, C 1-6 alkyl, C 4-9 heteroaryl containing at least one heteroatom selected from the group consisting of N, O and S, C 4-9 heterocyclyl containing at least one heteroatom selected from the group consisting of N, O and S, or C 6-10 aryl unsubstituted or substituted by at least one selected from the group consisting of halogen, hydroxyl, C 1-6 alkoxy and C 1-6 alkyl.