ABSTRACT
Typical laboratory experimental procedure for enzyme-and microbial-catalyzed reactions are described in this section.
EXPERIMENT 1: Biotransformation with and without cosolvent conditions The reduction of 1-phenyl-4-nitro-1-butanone (1) using Pichia etchellsii is given as an example. WITHOUT COSOLVENT. A solution of nitroketone (75 mg) (1) in ethanol (1.5 ml) was added to a stirred suspension (50 ml) of fresh cells of P. etchellsii (2.5g) resuspended in 0.1 M phosphate buffer (pH 6.0) at 28ºC. After 48 h the conversion was about 80%. Sodium chloride was added and the suspension extracted with diethyl ether. The organic layer was dried over sodium sulphate, filtered, and concentrated to give crude (S) alcohol (2). The purification was carried out to afford pure(S)-(-)-1-phenyl-4-nitro-1-butanol (2) (57 mg) in 75% yield and 70% ee. WITH ORGANIC COSOLVENT. A solution of nitroketone (75 mg) [1] in ethanol (1.5 ml) was added to a suspension of fresh cells of P. etchellsii (2.5 g) resuspended in a mixture of 1.0 M phosphate buffer (15 ml, pH 6.0) and organic solvent (35 ml). The mixture was stirred at 28ºC for 48 h. Usual workup and purification gave pure (S)-(-)-1phenyl-4-nitro-1-butanol (2) (57 mg) in 75% yield and 97% ee [α]D25 −50.6º(c=0.52, CHCl3) (Fig. 5.1).
