Synthesis and antifungal and antibacterial bioactivity of cyclic diamines containing boronate esters

Novel N2B heterocycles (1-5) are formed from the reaction of ethylenediamine derivatives with 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzaldehyde (2-HC(O)C(6)H(4)Bpin; pin = 1,2-O2C2Me4). X-ray diffraction studies have been carried out on four examples and show that reactions are selective in giving the isomer where the least substituted amine coordinates to the Lewis-acidic boron atom. Reaction of 2-HC(O)C(6)H(4)Bpin with diethylenetriamine gave a heterocycle (6) with a pendant primary amine group, which reacts further with 2-pyridinecarboxaldehyde to give a potential ligand (7) for transition metals. All new compounds show considerable antifungal activity against Aspergillus niger and Aspergillus flavus and moderate antibacterial activity against Bacillus cereus.