L-(+)-Cysteine → 4-Methoxybenzaldehyde

Participants

Reaction Steps

Preparation of (R)-2-(4-methoxy-phenyl)-thiazolidine-4-carboxylic acid (A compound of Formula IIIa): 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 4.00 L of water. The mixture was stirred until all of the L-cysteine dissolved. A solution of p-methoxybenzaldehyde (426.0 g, 3.13 mol) in 3.50 L of ethanol was prepared and added to the reaction such that the internal reaction temperature was kept below 30° C. The reaction becomes a thick white slurry during the addition of the p-methoxybenzaldehyde solution. After 30 minutes, 3.50 L of ethanol was added to the reaction. Stirring was continued for 1 hour and then the solid was isolated by filtration. A 1.50 L portion of ethanol was used to wash the solid. The solid was dried in a vacuum oven at 50° C. for 48 hours. Approximately 610 g of 2-(4-methoxy-phenyl)-thiazolidine-4-carboxylic acid was obtained (90% yield). 1H NMR (300 MHz, DMSO) δ 7.41-7.31 (m, 4H), 6.93-6.83 (m, 4H), 5.56 (s, 1H), 5.42 (s, 1H), 4.23 (dd, J=6.7, 4.4 Hz, 1H), 3.84 (dd, J=7.6, 7.1 Hz, 1H), 3.73 (s, 3H), 3.71 (s, 3H), 3.37-3.23 (m, 2H), 3.16-3.00 (m, 2H).

Provenance & Evidence