The treatment of 4-(dimethylamino)benzyl alcohol (I) with concentrated HBr at 120 C in a sealed tube provided benzyl bromide (II). This was then condensed with N-Boc-L-cysteine (III) in the presence of N,N-diisopropyl ethylamine to furnish the benzyl thioether (IV). Subsequent cleavage of the Boc group of (IV) employing HCl in dioxan yielded the intermediate aminoacid (V).

(S)-3-Benzoylthio-2-methylpropionic acid (VI) was activated as the acid chloride (VII) by treatment with SOCl2 or optionally converted to the active ester (VIII) upon condensation with p-nitrophenol in the presence of DCC. Coupling of aminoacid (V) with either acid chloride (VII) under Schotten-Baumann conditions or with p-nitrophenyl ester (VIII) in the presence of Et3N gave rise to the corresponding amide (IX). The benzoyl thioester of (IX) was finally cleaved employing aqueous ammonia to afford the title thiol.

The treatment of 4-(dimethylamino)benzyl alcohol (I) with concentrated HBr at 120 C in a sealed tube provided benzyl bromide (II). This was then condensed with N-Boc-L-cysteine (III) in the presence of N,N-diisopropyl ethylamine to furnish the benzyl thioether (IV). Subsequent cleavage of the Boc group of (IV) employing HCl in dioxan yielded the intermediate aminoacid (V).

(S)-3-Benzoylthio-2-methylpropionic acid (VI) was activated as the acid chloride (VII) by treatment with SOCl2 or optionally converted to the active ester (VIII) upon condensation with p-nitrophenol in the presence of DCC. Coupling of aminoacid (V) with either acid chloride (VII) under Schotten-Baumann conditions or with p-nitrophenyl ester (VIII) in the presence of Et3N gave rise to the corresponding amide (IX). The benzoyl thioester of (IX) was finally cleaved employing aqueous ammonia to afford the title thiol.