Piperidine-1,4,4-tricarboxylic acid 1-tert-butyl ester 4-Methyl ester; 1-[(tert-butoxy)carbonyl]-4-(methoxycarbonyl)piperidine-4-carboxylic acid; 1-BOC-4-(METHOXYCARBONYL)PIPERIDINE-4-CARBOXYLIC ACID;