comparison of these results to those obtained with the methyl ester of a23187 ( log kh = 1.32 ) and literature values for other model compounds allowed assignment of the more basic equilibrium to the carboxylic acid moiety and the more acidic one to the n-methylamino substituent of the benzoxazole ring . log kh of the carboxylic acid increased from 5.69 +/- 0.05 to 9.37 +/- 0.05 over the range of solvent polarity encompassed by water to 95 % methanol-water .
C0014898
ester
C0007066
carboxylic acid