Patent ID: 7294646

Claim:
A compound of structural formula I: or a pharmaceutically acceptable salt, enantiomer, diastereomer, tautomer or mixture thereof, wherein, R 1 and R 1a independently are: R 2 is: (a) CO 2 C 1-6 alkyl, (b) H, (c) OH, or (d) C 1-6 alkyl, when a double bond is not present at b; R 3 is: (a) H, (b) (C═O)OC 1-6 alkyl or (c) C 1-6 alkyl optionally substituted with OH, N(R 6 ) 2 , or CO 2 R 6 ; R 4 is (a) H, provided that R 3 is not H, (b) C 1-6 alkyl optionally substituted with OH, N(R 6 ) 2 , or CO 2 R 6 or R 5 is: (a) H, (b) OH, or (c) OC 1-6 alkyl; R 6 is: (a) H, or (b) C 1-6 alkyl; R 7 is H, or C 1-6 alkyl optionally substituted with OH, N(R 6 ) 2 , or CO 2 R 6 ; R 8 is H, C 1-6 alkyl, CH 2 -phenyl, CH 2 -hydroxyphenyl, CH 2 -indolyl, CH 2 -imidazolyl, CH 2 OR 6 , CH(OR 6 )CH 3 , (CH 2 ) n C(O)NR 6 , (CH 2 ) n CO 2 R 6 , (CH 2 ) n SR 6 , (CH 2 ) n (N + R 6 ) 3 , n is 0-4, and is a double bond optionally and independently present at a or b.