Prepn. of hexa-methyl cystine - by treatment of cystine with di:methyl sulphate and base e.g. potassium-or sodium hydroxide

摘要

The water-soluble cystine betaine, hexamethyl cystine (I) is prepd. as follows: (a) cystine and water are mixed without at 0-4 deg.C in a first phase, and (b) in a second phase the mixt. is treated dropwise at 0-4 deg.C with a base to solubilise the cystine and simultaneously with the same base and dimethyl sulphate, (c) after stirring, (I) is pptd. and/or isolated. The base used is pref. KOH or NaOH, with one third being used to solubilise the cystine with the other two thirds being added with the dimethyl sulphate. The cystine is pref. the L-isomer, obtd. from chicken feathers. Pptn. of (I) is effected by addn. of glacial acetic acid to the reaction mixt. USE/ADVANTAGE - Cystine is known to aid hair, fur, and nail growth but its lack of water solubility limits its local application. Known methods of preparing the water-soluble form, (I), give poor yields, and so it has not been exploited commercially. The new process gives much improved yields.