A Computational Investigation of the Geometrical Structure and Protodeboronation of Boroglycine, H2N−CH2−B(OH)2

In this article the geometrical structure of the simple, achiral, α-amino boronic acid boroglycine, H2N−CH2−B(OH)2, was investigated using density functional theory (DFT), second-order Møller−Plesset (MP2) perturbation theory, and coupled cluster methodology with single- and double-excitations (CCSD); the effects of an aqueous environment were incorporated into the results by using a few explicit water molecules and/or self-consistent reaction field (SCRF) calculations with the IEF polarizable continuum model (PCM). Neutral reaction mechanisms were investigated for the direct protodeboronation (hydrolysis) of boroglycine (H2O + H2N−CH2−B(OH)2 → B(OH)3 + H2N−CH3), for which was −21.9 kcal/mol at the MP2(FC)/aug-cc-pVDZ level, and for the 1,2-carbon-to-nitrogen shift of the −B(OH)2 moiety (H2N−CH2−B(OH)2 → H3C−NH−B(OH)2), for which the corresponding value of was −18.2 kcal/mol. A boron−oxygen double-bonded intermediate was found to play an important role in the 1,2-rearrangement mechanism.