The synthesis of 4-S-cysteinyl-[U-14C]phenol, an experimental antimelanoma agent

4-S-Cysteinylphenol (4-CP) has been shown to exert selective toxicity to melanocytes, causing growth inhibition of experimental malignant melanoma. 4-S-Cysteinyl-[U-14C]phenol (4-[U-14C]CP) has now been synthesized by reaction of [U-14C]phenol with excess L-cystine in HBr. After crystallization of unreacted cystine from the reaction mixture, 4-[U-14C]CP was recovered by HPLC in 57.6% radiochemical yield with a specific activity of 26.2 MBq mg-1 (15.2 mCi mmol-1). Radiochemical purity was greater than 99%. 2-S-Cysteinyl-[U-14C]phenol (2-[U-14C]CP), a side product with no antimelanoma activity, was recovered in 6% radiochemical yield.