638-23-3

white to slightly off-white amorphous powder

Rhinathiol,Kramer,Switz.

ChEBI: S-carboxymethyl-L-cysteine is an L-cysteine thioether that is L-cysteine in which the hydrogen of the thiol group has been replaced by a carboxymethyl group. It has a role as a mucolytic. It is a L-cysteine thioether and a non-proteinogenic L-alpha-amino acid. It is a conjugate acid of a S-carboxylatomethyl-L-cysteine(1-).

There were placed 120g of L-cysteine (0.5 mol) in a 2 liter three-necked flask equipped with a stirrer thermometer and methanol/dry ice cooling and 1.5 liters of liquid ammonia were allowed to enter at -40°C. Then there were added under continuous cooling 50 g (2.17 mols) of sodium metal in portions of 1 to 2 g during the course of one hour. The end of the reaction was recognized by the continuation of the blue color. After the end of the reaction the excess sodium was destroyed by the addition of ammonium chloride and the ammonia vaporized at normal pressure. The residue was taken up in 500 ml of water and concentrated in a vacuum to 200 ml in order to remove residual ammonia, and again treated with 300 ml of water. The entire operations were carried out under a nitrogen atmosphere.
The aqueous solution of the disodium salt of L-cysteine obtained is then reacted at 20°C to 30°C under a nitrogen atmosphere in the course of 30 minutes with stirring with a solution of 104 g of chloroacetic acid (1.1 mols) and 4 g of sodium pyrosulfite in 200 ml of water. It is also allowed to post react for 15 minutes at 20°C, the solution clarified over activated carbon and the filtrate treated with 90 ml of concentrated hydrochloric acid to a pH of 2.5.
Thereby the S-carboxymethyl-L-cysteine precipitates out in crystalline form. The product is filtered off with suction, well stirred in 500 ml of water, again filtered with suction and dried in a vacuum at 70°C. The yield is 92% based on L-cysteine.

Loviscol (Wyeth-Ayerst); Mucofan (Wyeth-Ayerst).

Mucolytic, Expectorant, Nasal antiinfective

S-Carboxymethyl-L-cysteine is studied as a small molecule mucoactive drug in vivo. These studies include analyzing the oxidative metabolism of S-carboxymethyl-L-cysteine by enzymes such as phenylalanine monooxygenase(s).