Development of an efficient, scalable, aldolase-catalyzed process for enantioselective synthesis of statin intermediates

A process is reported for efficient, enantioselective production of key intermediates for the common chiral side chain of statin-type cholesterol-lowering drugs such as Lipitor (atorvastatin) and Crestor (rosuvastatin). The process features a one-pot tandem aldol reaction catalyzed by a deoxyribose-5-phosphate aldolase (DERA) to form a 6-carbon intermediate with installation of two stereogenic centers from 2-carbon starting materials. An improvement of almost 400-fold in volumetric productivity relative to the published enzymatic reaction conditions has been achieved, resulting in a commercially attractive process that has been run on up to a 100-g scale in a single batch at a rate of 30.6 g/liter per h. Catalyst load has been improved by 10-fold as well, from 20 to 2.0 wt % DERA. These improvements were achieved by a combination of discovery from environmental DNA of DERAs with improved activity and reaction optimization to overcome substrate inhibition. The two stereogenic centers are set by DERA with enantiomeric excess at >99.9% and diastereomeric excess at 96.6%. In addition, down-stream chemical steps have been developed to convert the enzymatic product efficiently to versatile intermediates applicable to preparation of atorvastatin and rosuvastatin.