10.3390/molecules25174009
The research focuses on the synthesis of potential haptens based on the morphine skeleton, aimed at developing a vaccination strategy against drug addiction and abuse. Haptens, which require a free amino or carboxylic group for coupling with an immunogenic carrier protein, were synthesized through reactions involving ethyl acrylate, ethyl bromoacetate, and N-(chloroacetyl)glycine ethyl ester. The study detailed the synthesis process, including N-demethylation and N-alkylation, and the subsequent hydrolysis to obtain N-carboxymethyl- and N-carboxyethyl-normorphine derivatives. The acid-base properties of these molecules were characterized using pH-potentiometry and NMR-pH titrations, with the protonation constants being determined to understand their pharmacokinetic behavior. The experiments utilized various reagents, solvents, and analytical techniques such as NMR, HR-MS, and potentiometric titrations to confirm the structures and physiochemical properties of the synthesized compounds.