Sodium borohydride → tert-Butyl (1R)-1-benzyl-2-hydroxypropylcarbamate

Participants

Reaction Steps

A solution of 21 g of tert-butyl (1R)-1-benzyl-2-oxopropylcarbamate in 200 cm3 of ethanol under an inert atmosphere is cooled to a temperature in the region of 10° C., followed by portionwise addition of 4.55 g of sodium borohydride. The temperature of the reaction medium is allowed to rise to room temperature with stirring, and the stirring is then continued for 18 hours. The reaction medium is concentrated under reduced pressure (2 kPa) at a temperature in the region of 40° C., to give white crystals which are taken up in 150 cm3 of water. This mixture is stirred for 2 hours at room temperature and then filtered through a sinter funnel. The filter cake is washed with twice 150 cm3 of water. After drying overnight in a fume cupboard, 19.37 g of tert-butyl (1R)-1-benzyl-2-hydroxypropylcarbamate are obtained in the form of white crystals melting at 127° C. 1H NMR spectrum (300 MHz, (CD3)2SO-d6 with addition of a few drops of CD3COOD-d4, δ in ppm). A mixture of two diastereoisomers in 70/30 proportions is observed: 1.04 and 1.10 (2d, J=6 Hz: 3H); 1.29 and 1.32 (2s: 9H); from 2.40 to 3.10 (mt: 2H); from 3.35 to 3.70 (mt: 2H); 6.40 and 6.54 (2d, J=9 Hz: 1H); from 7.10 to 7.35 (mt: 5H).

Provenance & Evidence