An L-cysteinyl ester resulting from the formal condensation of the carboxylic acid group of L-cysteine with methanol. It is used (as the hydrochloride salt) as a mucolytic for the treatment of respiratory disorders associated with productive cough. ChEBI: Methyl L-cysteinate is an L-cysteinyl ester resulting from the formal condensation of the carboxylic acid group of L-cysteine with methanol. It is used (as the hydrochloride salt) as a mucolytic for the treatment of respiratory disorders associated with productive cough. It has a role as a mucolytic. It is a L-cysteinyl ester, a primary amino compound and a thiol. It is functionally related to a L-cysteine and a methanol.