| abstract |
Compounds of the invention include those of the following formula: <IMAGE> In this formula, A is oxygen, sulfur or selenium; X' is a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C2-C3 alkenyl group, a substituted or unsubstituted C2-C3 alkynyl group, a substituted or unsubstituted amino group, sulfur or oxygen; Y is oxygen, sulfur or NH; B is hydrogen or a halogen; C is hydrogen, a halogen or a substituted or unsubstituted C1-C6 alkyl group; and R6 is hydrogen or a moiety that forms with the attached CO2 a readily hydrolyzable ester group. |