Hydrochloric Acid → N-Isobutyrylcysteine

Participants

Reaction Steps

A suspension of 35.2 g (0.20 mol) of L-cysteine hydrochloride monohydrate in 100 ml of a mixture of 80% of tetrahydrofuran (THF) and 20% of water was stirred under nitrogen at room temperature and treated with 44.0 g (0.40 mol) of sodium isobutyrate. The reaction mixture (white slurry) was cooled to 0°-5° C. and, under nitrogen, 35 ml (0.21 mol) of isobutyryl anhydride was added dropwise. The resulting mobile suspension was stirred for 6h at room temperature, allowed to stand overnight, and finally heated under reflux for 4 h. The reaction mixture was cooled on an ice bath and 18 ml of concentrated hydrogen chloride was added. The organic phase was evaporated to give a colourless oil. The oil was washed with hexane and thereafter treated with ether to give 12.9 g of the title compound as a white solid, mp 103°-104° C. (recrystallized from butyl acetate), [α]D25 =+23.4° C. (c 5.0, H2O, pH=7.0), 1H-NMR (CDCl3): δ 1.2 (6H, d, CH3), 1.4 (1H, t, SH), 2.5 (1H, sept, CH), 3.1 (2H, m, CH2), 4.9 (1H, dt, NCH), 6.7 (1H, d, NH), 10.6 (1H, s, OH). 13C-NMR (CDCl3): δ 19, 19.5; 26.5; 36; 54, 172, 178. ms: 335 (M+ +2TMS, after silylation).

Provenance & Evidence