. "; R7 is C(O)OR17 in which R17 is hydrogen, alkyl containing from 1 to 7 carbons or alkenyl having 3 to 7 carbon atoms, aryl or heteroaryl, particularly pyridyl, phenyl, tolyl, ethylphenyl, butylphenyl, halophenyl, alkenyl containing 3 to 7 carbons and having formula Cn H.sub.(2n-1), or is an alkali metal or alkaline earth metal salt, such as sodium, potassium, calcium, and ammonium; and R2 is a st" . . . .