Synthesis and Structural Investigation of Internally Coordinated α-Amidoboronic Acids

[structure: see text] Six new N-acyl-boroGly derivatives, along with their N-acyl-boroSar analogues, have been synthesized by modification of conventional procedures. Structural characterization of these alpha-amidoboronic acids was accomplished by extensive use of 11B and 1H NMR spectroscopy. These compounds were prepared to determine the extent of intramolecular B-O dative bond formation within the context of a five-membered (:O=C-N-C-B) ring motif. It is shown that the formation of such dative bonds depends on the nature of the substituents at both the acyl carbon and the nitrogen atoms. Computational evidence from second-order Møller-Plesset perturbation theory is provided in support of these findings.