Chemo-enzymatic synthesis of the antidepressant duloxetine and its enantiomer.

Sodium borohydride reduction of 3-chloro-1-(2-thienyl)-1-propanone gave the corresponding racemic alcohol which was kinetically resolved with lipase B from Candida antarctica as catalyst to yield the chiral building blocks (S)-3-chloro-1-(2-thienyl)-1-propanol and the corresponding (R)-butanoate. The enantiopure chiral building blocks were converted into Duloxetine and its enantiomer.