L-(+)-Cysteine → (4R)-2-(4-Methoxyphenyl)-4-thiazolidinecarboxylic acid

Participants

Reaction Steps

A 22 L three-necked round bottom flask fitted with an internal temperature probe and a mechanical stirrer was charged with L-cysteine hydrochloride monohydrate (500.0 g, 2.85 mol), sodium acetate (260.0 g, 3.17 mol) and water (4 L). The mixture was stirred until all of the L-cysteine dissolved. A solution of 4-methoxybenzaldehyde (426.0 g, 3.13 mol) in ethanol (3.5 L) was prepared and added to the reaction dropwise such that the internal reaction temperature was kept below 30° C. The reaction went from a clear solution to a thick white slurry during the addition of the 4-methoxybenzaldehyde solution. After 30 minutes, ethanol (3.5 L) was added to the reaction and the slurry thickened. Stirring was continued for 1 hour and then the solid was isolated by filtration, and the solid was washed with additional ethanol. The solid was dried in a vacuum oven at 50° C. over 48 hours to afford the title compound (610 g, 90%).

Provenance & Evidence