The first expedient entry to the human melanogen 2-S-cysteinyldopa exploiting the anomalous regioselectivity of 3,4-dihydroxycinnamic acid–thiol conjugation

The first convenient synthesis of 2-S-cysteinyl-3,4-dihydroxyphenylalanine (2-S-cysteinyldopa) in 30% overall yield is reported, which capitalizes on the anomalous regiochemistry of the oxidative coupling of 3,4-dihydroxycinnamic acid derivatives with thiol compounds, leading to 2-S rather than the usual 5-S conjugates.