Hydrochloric Acid → Methyl l-cysteate

Beteiligte Stoffe

Reaktionsschritte

A mixture of 1 g of L-cysteic acid, 8 ml of 4 N hydrochloric acid in dioxane and 30 ml dry methanol was placed in a bottle. The bottle was capped and stored for approximately 96 hours at room temperature. Thin layer chromatography of the clear solution [Analtech silica gel plates, n-butanol:ethyl acetate:acetic acid:water (1:1:1:1), chlorine/potassium iodide-starch reagent (Stewart J. M. and Young J. D. in Solid Phase Peptide Synthesis, Pierce Chemical Company, PP.120 (1984)] indicated greater than 95 % conversion of cysteic acid to the ester. Solvents were removed under vacuum to get 1.05 g of a sticky solid. Mass spec analysis gave the m/z for the major M+1 ion as 184.3. Fragmentation of this ion gave the M+1 ion of 123.9, which represents the loss of one of the carboxymethyl groups. The solids were used without further purification in the next step.

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