"Penicilloic acid" . . . . . . . . . "penicillanic acid" . . "Penicilloic acid" . . . . . . . . "penicilloic acid" . . . . . . "(2R,4S)-2-[(R)-Carboxy(formamido)methyl]-5,5-dimethyl-1,3-thiazolidine-4-carboxylic acid" . . . . . "Penicilloic acid" .