Definition
ChEBI: S-methyl-L-methionine is a sulfonium compound that is the conjugate acid of S-methyl-L-methioninate. It has a role as a Saccharomyces cerevisiae metabolite and an Escherichia coli metabolite. It is a conjugate acid of a S-methyl-L-methioninate. It is a tautomer of a S-methyl-L-methionine zwitterion.
Purification Methods
Likely impurities are methionine, methionine sulfoxide and methionine sulfone. Crystallise Vitamin U from water by adding a large excess of EtOH. It is hygroscopic. It should be stored in a cool, dry place and protected from light. It has also been purified on a column of Dowex 50 H+ form, washed with H2O and eluted with 6N ammonia, lyophilised, the residue is dissolved in dilute HCl, lyophilised again and then it is obtained as colourless prisms by vapour diffusion of Et2O in a 1:1 (v/v) mixture of MeOH/EtOH in which the hydrochloride is dissolved [Del Re Acta Cryst B 33 3289 1977]. The iodide salt, m ~ 150o(dec), is obtained by dissolving it in 50% aqueous EtOH and adding ~3.5 volumes of absolute EtOH. The bromide salt has m 140o(dec) [Toennies & Kolb J Amer Chem Soc 67 849 1945].
