Regio- and Enantioselective Sequential Dehalogenation of rac-1,3-Dibromobutane by Haloalkane Dehalogenase LinB
Gross, J., Prokop, Z., Janssen, D., Faber, K., Hall, M.
CHEMBIOCHEM 17: 1437-1441 (2016)
The hydrolytic dehalogenation of rac-1,3-dibromobutane catalyzed by haloalkane dehalogenase LinB fromSphingobium japonicum UT26 proceeds in a sequential fashion via initial formation of intermediate haloalcohols followed by a second hydrolytic step to produce the final diol. Detailed investigation of the course of the reaction revealed favored nucleophilic displacement of the sec-halogen in the first hydrolytic event with pronounced (R)-enantioselectivity. The second hydrolysis step proceeded with a regioselectivity switch at the primary position with preference for the (S)-enantiomer. Due to complex competition between all eight possible pathways, intermediate haloalcohols could be formed with moderate to good ee values [(S)-4-bromobutan-2-ol in up to 87% ee]. Similarly, (S)-1,3-butanediol was formed in max. ee 35% before full hydrolysis furnished the racemic diol product.