A homogeneous redox catalytic process for the paired synthesis of l-cysteine and l-cysteic acid from l-cystine

► Mechanism is proposed for the paired synthesis of l-cysteine and l-cysteic acid. ► In-situ deposited tin acts as a redox catalyst for the electroreduction process. ► Electrogenerated bromine acts as a homogeneous redox mediator in electro-oxidation. ► We obtain yield of 80% for l-cysteine and 60% for l-cysteic acid.