Preparation of artificial urushi via an environmentally benign process

Artificial urushi has been developed by laccase-catalyzed curing of new urushiol analogues. The analogues were designed and conveniently synthesized by regioselective acylation of phenol derivatives having a primary alcohol with unsaturated fatty acids using lipase as catalyst. The curing of the catechol derivative having a linolenoyl group proceed ed in the presence of acetone powder from Chinese urushi, yielding the crosslinked film ("artificial urushi") with high hardness and gloss surface, which are comparable with those of natural urushi coating. The analogues obtained from vanillyl alcohol were also cured. FI-IR monitoring of the curing showed that the crosslinking mechanism was similar to that of the natural urushi. The curing of the urushiol analogues in the presence of starch-urea phosphate took place to give the artificial urushi consisting exclusively of synthetic compounds.