Enhanced anti-fungal activity of the organo-soluble borate ester, tetra-n-butylammonium bis(ortho-hydroxymethylphenolato)borate

The borate ester, tetra- n- butylammonium bis( ortho- hydroxymethylphenolato) borate, NBu4[ B( o-hmp)(2) ], was synthesized and characterized byNMRspectroscopy ( H-1, C-13, B-11), ES- MS, and X- ray crystallography. The anti- fungal activity of this compound, as well as its sodium salt, the parent phenol, tetra- n- butylammonium bromide, and boric acid were evaluated against two wood decay fungi. The tetraalkylammonium borate NBu4[ B( o-hmp)(2)] shows the highest activity out of the compounds examined. This finding suggests that the formation of lipophilic borate esters is a promising approach for the development of leach- resistant, borate- based wood preservatives.