Synthesis of a novel diarylphosphinic acid: a distorted ground state mimic and transition state analogue for amide hydrolysis

We describe herein the synthesis of a new unsymmetrical diarylphosphinic acid, a hapten aimed to produce catalytic antibodies for the hydrolysis of heterocyclic amides. The phosphinate functionality was selected as a mimic both of the tetrahedral intermediate and the transition state of higher energy along the reaction profile. The phenyl and 2,4,6-(trimethyl)-phenyl groups flanking the phosphinate were chosen in order to impose rotation around the P–C bond, a choice supported by ab initio calculations. This new hapten should elicit catalytic antibodies whose binding site could affect the distortion at nitrogen as well as the twist along the N–C(O) bond for heterocyclic amides. This hapten along with a series of new sterically hindered unsymmetrical phosphinic acid derivatives was prepared by a key palladium-catalysed step.