ethyl 6-methyl-4-oxo-6-phenyl-5H-pyran-3-carboxylate 6-methyl-4-oxo-6-phenyl-5H-pyran-3-carboxylic acid ethyl ester 4-keto-6-methyl-6-phenyl-5H-pyran-3-carboxylic acid ethyl ester NSC699223 NCI60_035533