Compounds of the structure: STR1 wherein R1, R2, R3, R4, R5, and R6 are hydrogen, alkyl, alkenyl, alkynyl, phenyl-alkyl, or cycloalkyl, n is an integer from 0 to 4 inclusive, M is alkenyl, alkynyl, cycloalkyl, cycloalkyl-alkyl, polycycloalkyl, polycyclo-alkyl-alkyl, aryl, aralkyl, heteroaryl, heteroaryl-alkyl, hetero-cycloalkyl, hetero-cycloalkyl-alkyl, alkoxyalkyl, alkylthioalkyl, alkylamino-alkyl, dialkylamino-alkyl, fused aryl-cycloalkyl, fused aryl-cycloalkyl-alkyl, fused heteroaryl-cycloalkyl, or fused heteroaryl-cycloalkyl-alkyl, Y is hydroxy, alkoxy, amino, or substituted amino, aminoalkanoyl, aryloxy, aminoalkoxy, or hydroxyalkoxy, and R7 is hydrogen, alkanoyl, carboxylalkanoyl, hydroxyalkanoyl, amino-alkanoyl, cyano, amidino, carbalkoxy, ZS, or STR2 wherein Z is hydrogen, alkyl, hyroxyalkyl, aminoalkyl or the radical STR3 wherein R1, R2, R3, R4, R5, R6, n, M and Y are as described above; and where Y is hydroxy their non-toxic, pharmaceutically acceptable alkali metal, alkaline earth metal, and amine salts.