Novel Trivalent C3-Symmetrical Phenylboronic Acid Pinacol Esters and Their Biological Evaluation

We report the preparation of newly designed trivalent C-3-symmetrical cyclic phenylboronic acid derivatives constructed on a symmetrical benzene or a cyclohexane ring. The synthesis of these C-3-symmetrical molecules 4 was accomplished by an amide bond formation reaction using amino-substituted phenylboronic acid pinacol esters 2 and C-3-symmetrical benzene-1,3,5-tricarboxylic acid trichloride 3a or cyclohexane-1,3,5-tricarboxylic acid trichloride 3b in the presence of Et3N. We confirmed that this procedure is conventionally applicable to the preparation of targeted C-3-symmetrical cyclic boronic acid derivatives 4 in good to excellent yields. We also report the results of biological evaluation of the prepared compounds.