Ethylcysteine sulfoxide

Kubec R, Svobodova M and Velisek J (2000), Distribution of 5-alk(en)ylcysteine sulfoxides in some Allium species. Identification of a new flavour precursor S-ethylcysteine sulfoxide (ethiin) , JAgric Food Chem, 48, 428-433. 

All these enzymes have similar specificity and require the L-cysteine sulfoxide portion of the molecule. S-alkyl cysteines are not substrates 18, 24, 27, 39) neither are sulfoxides of N-substituted L-cysteine, / -di-methyl-L-cysteine, y8-thiopropionic acid 18), D-cysteine 19), and dl-methionine 18, 24, 39), nor do the enzymes act on L-cysteine itself 24, 27, 39), cysteic acid, cysteinesulfinic acid 24, 27), or cycloalliin 24, 39). There may be some action on S-ethylcysteine sulfone (42). 

Arylhydroxylamines are readily converted into nitroso compounds with DAD at 0°C (eq 1). One example of the conversion of an A,A-dimethylhydrazone to a nitrile has been reported. Sulfur-containing amino acids like methionine and S-ethylcysteine can be oxidized to their sulfoxides in virtually quantitative yields, although another reaction pathway occurs with most other thioethers. Thioethers and ethers usually react with DAD to yield a-hydrazo derivatives by hydrogen abstraction. The initial ether/DAD adducts can be formed thermally at 100 °C or photochemically at much lower temperatures. ... 

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