Lipase catalyzed reactions of aliphatic and arylaliphatic carbonic acid esters

Symmetrical dialkyl carbonates and dibenzyl carbonates reacted with various nucleophiles in the presence of Candida antarctica lipase B in organic solvents. For example, reaction of dibutyl and dibenzyl carbonate with an alcohol gave a mixture of the mono- and disubstituted products. Aminolysis, however, afforded only the carbamates, without subsequent reaction to the ureum derivatives. The reaction rates were rather low compared with carboxylic esters; the reactivity increased in the order dimethyl<diethyl<dibutyl≈dibenzyl carbonate. Aminolysis of dibenzyl carbonate by chiral benzylamines gave the corresponding enantiomerically pure benzyloxycarbonyl amines, thus, providing a direct, phosgene-free route to the Z-protected amine enantiomer from the racemate.