Synthesis of isothiocyanate-derived mercapturic acids

Twelve mercapturic acids derived from saturated and unsaturated aliphatic and aromatic isothiocyanates were synthesised, by adding isothiocyanate to a solution of N-acetyl-L-cysteine and sodium bicarbonate, in a typical yield of 77%. Isothiocyanates were synthesised first by adding the corresponding alkyl bromide to phthalimide potassium salt. The obtained N-alkyl-phthalimide was hydrazinolysed yielding the alkyl amine, which subsequently was reacted with thiophosgene yielding the isothiocyanate with an overall yield of 16%. Mercapturic acids in urine can serve as a biomarker of intake to determine the health promoting potential of isothiocyanates present in cruciferous vegetables.