Patent ID: 8895569

Claim:
A compound of the formula wherein R 1 and R 2 are independently selected from hydrogen, CO 2 C 1 -C 4 alkyl, C 1 -C 6 alkyl, C 2 -C 6 alkenyl and C 2 -C 6 alkynyl, wherein the alkyl moieties of said alkyl, alkenyl, and alkynyl groups may be linear, branched chain or a combination of linear and branched chain where n is 0 to 3, where n is 1 to 2, C 3 -C 7 cycloalkyl, a three to twelve membered heterocyclic ring containing up to 3-heteroatoms where the heteroatoms are independently selected from N, O and S and where each heterocyclic ring may be optionally substituted at one or more carbon atoms by from 1 to 3 substituents independently selected from C 1 -C 6 alkoxy, and O—C 1 -C 6 alkyl; R 3 and R 4 are independently selected from hydrogen and C 1 -C 6 alkyl; R 5 and R 6 are independently selected from hydrogen and —CO 2 C 4 H 9 ; A is selected from a covalent bond, O, S, Se, C 1 -C 6 alkyl, and (CH 2 ) n O, where n is an integer from 0 to 3; X is selected from a covalent bond, O, S and Se; B is selected from a covalent bond, —CH 2 , —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, trans-CH═CH—, cis-CH═CH—, —C≡C—, —CHR 7 —CHR 8 —, cis or trans-CR 7 ═CR 8 —, wherein R 7 and R 8 are independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, and C 3 -C 7 cycloalkyl; and Y is selected from of OH, SH, OR 9 wherein R 9 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl and C 2 -C 6 alkynyl, C 3 -C 7 cycloalkyl, and (CH 2 ) n OH, wherein n is an integer from 1 to 6 and NR 9 R 10 wherein R 9 and R 10 are independently selected from C 1 -C 6 alkyl and C 3 -C 7 cycloalkyl; or a pharmaceutically acceptable salt thereof.