Action of nitrogen trichloride on certain proteins II. Synthesis of methionine sulphoximine and other sulphoximines

Methionine sulphoximine $(\text{I}$, $R=\text{CH}_{2}\text{CH}_{2}\text{CH}(\text{NH}_{2})\text{COOH}$, $R^{\prime}$ = $\text{CH}_{3})$ can be synthesized by the action of hydrazoic acid on methionine sulphoxide in the presence of concentrated sulphuric acid as a catalyst and is shown to be identical with the toxic factor isolated from nitrogen trichloride-treated proteins. S-methylcysteine sulphoximine $(\text{I}$, $R=-\text{CH}_{2}\text{CH}(\text{NH}_{2})\text{COOH}$, $R^{\prime}$ = $\text{CH}_{3})$ and dimethyl-sulphoximine $(\text{I},R,R^{\prime}$ = $\text{CH}_{3})$ are prepared by a similar method from the corresponding sulphoxides; in rabbits, S-methylcysteine sulphoximine does not produce the toxic symptoms obtained with methionine sulphoximine. Possible mechanisms are discussed for the reaction between hydrazoic acid and a sulphoxide.