Chemo-enzymatic synthesis of 11-hydroxyundecanoic acid and 1,11-undecanedioic acid from ricinoleic acid†
A practical chemoenzymatic synthetic method for 11-hydroxyundecanoic acid and 1,11-undecanedioic acid from ricinoleic acid (12-hydroxyoleic acid) was investigated. Biotransformation of ricinoleic acid into the ester (3) via 12-ketooleic acid (2) was driven by recombinant Escherichia coli cells expressing an alcohol dehydrogenase from Micrococcus luteus and the Baeyer–Villiger monooxygenase from Pseudomonas putida KT2440. The carbon–carbon double bond of the ester (3) was chemically reduced, and the ester bond was hydrolyzed to afford n-heptanoic acid (5) and 11-hydroxyundecanoic acid (7), which were converted into other related derivatives. For example, 11-hydroxyundecanoic acid was transformed into 1,11-undecanedioic acid (8) under fairly mild reaction conditions. Whole-cell biotransformation at high cell density (i.e., 20 g dry cells per L) allowed the final ester product concentration and volumetric productivity to reach 53 mM and 6.6 mM h−1, respectively. The overall molar yield of 1,11-undecanedioic acid from ricinoleic acid was 55% based on the biotransformation and chemical transformation conversion yields of 84% and 65%, respectively.