The Reaction of Cobalamins with Thiols: an Alternative Synthesis of Alkyl-cobamide Coenzyme Analogues
David Dolphin and AW Johnson
Proc. Chem. Soc.
Aqeous solutions of hydroxocobalamin change from red to violet in color when treated with one of the following: 2-mercaptoethanol, mercaptoacetic acid, cysteine, homocysteine, ethanethiol, PhCH2SH, and NaHS. Subsequent addition of MeI in the dark afforded methylcobalamin, which was identified by chromatography and spectra. With NaHS the yield is 90%. Other successful alkylating agents were p-MeC66H4SO3Me, 1-chloro-, 1-bromo-, and 1-iodopropane, 1-iodobutane, chloroacetic acid, α-chloropropionic acid, and acetyl chloride.