the synthesis of L-cysteine unsymmetricaldisulfides under mild conditions with good to excellent yields. Described method is based on the straightforward preparation of the organophosphorus sulfenyl bromide readily available from bis-(5,5-dimethyl-2-thiono-1,3,2-dioxaphosphorinanyl) disulfide. The unsymmetricaldisulfides can be obtained for L-cysteine derivatives and thiols bearing neutral or acidic