Pyridine → benzyl (S)-3-((R)-1-(1-benzyl-4-(2,5-difluorophenyl)-1H-imidazol-2-yl)-2,2-dimethylpropylamino)-2-(tert-butyldimethylsilyloxy)propylcarbamate

Participants

Reaction Steps

To a solution of benzyl 2-(tert-butyldimethylsilyloxy)-3-hydroxypropylcarbamate (1.0 eq.) in dichloromethane (0.1 M) was added pyridine (5.0 eq.) and Dess-Martin Periodinane® (1.5 eq.) at 0° C. The reaction mixture was stirred for 3 h and quenched with 5% NaHCO3 aqueous solution and 1.0 M aqueous Na2S2O3 solution. After stirred for 1 h, the organic layer was separated, washed with water and brine, dried, and concentrated. The crude aldehyde was added to a solution of (R)-1-(1-benzyl-4-(2,5-difluorophenyl)-1H-imidazol-2-yl)-2,2-dimethylpropan-1-amine (1.2 eq.), prepared according to the general procedure reported previously, in dichloromethane (0.2 M) with a drop of acetic acid at room temperature. After stirred for 0.5 h, sodium triacetoxyborohydride (1.5 eq.) was added to the reaction mixture at 0° C. followed by warming up to room temperature for 1 h. After quenched with saturated NaHCO3 aqueous solution, the reaction mixture was worked up with EtOAc which was washed with water and brine. The organic layer was separated, dried, and concentrated. The crude diastereomeric mixture was separated on silica gel with 20% EtOAc/Hexanes elution to provide the pure diastereomers, benzyl (S)-3-((R)-1-(1-benzyl-4-(2,5-difluorophenyl)-1H-imidazol-2-yl)-2,2-dimethylpropylamino)-2-(tert-butyldimethylsilyloxy)propylcarbamate and benzyl (R)-3-((R)-1-(1-benzyl-4-(2,5-difluorophenyl)-1H-imidazol-2-yl)-2,2-dimethylpropylamino)-2-(tert-butyldimethylsilyloxy)propylcarbamate, where the stereochemistry at the carbon attached to oxygen atom was arbitrarily assigned ((R,R) diastereomer was more polar than (R,S) isomer on TLC).

Provenance & Evidence