Lipase-catalyzed fatty acid exchange in digalactosyldiacylglycerol. Improvement of yield due to the addition of phenylboronic acid

Rhizopus arrhizus lipase immobilized on porous polypropylene was used in an acidolysis reaction in toluene at low water activity (0.11) to exchange the fatty acid in the sn-1-position of digalactosyldiacylglycerol (DGDG). Without extra precautions, an yield of only about 20% was obtained, mainly due to side reactions; incorporation of an extra acyl group on the primary hydroxyl of the digalactosyl moiety and acyl migration in partially deacylated reaction intermediates, followed by further hydrolysis. By the addition of phenylboronic acid (equimolar amount with respect to DGDG) both the side reactions were suppressed and the yield of DGDG containing the new fatty acid (heptadecanoic acid) in the sn-1-position increased to about 60%.