Methyl iodide → O-benzyl-L-tyrosine

Participants

Reaction Conditions

Reaction Steps

To a suspension of NaH in THF (5 mL) cooled to 0° C. was added dropwise a solution of N-(tert-butyloxycarbonyl)-O-(phenylmethyl)-L-tyrosine, 1-[4-(2,3-dichlorophenyl)methyl]piperazine amide (N-Boc derivative of Example 159) (339 mg, 1.0 equiv). Methyl iodide (402 mg, 5 equiv) was then added to the reaction mixture via syringe. After the reaction was stirred at 0° C. for 30 minutes, it was warmed up to room temperature and stirred for 3 hours. An excess of methyl iodide and NaH was added to the reaction mixture (to achieve approximately 70% conversion) over 48 hours. After aqueous work up, the mixture was directly treated with HCl/Et2O in MeOH to afford the racemized titled product along with racemized O-(phenylmethyl)-L-tyrosine, 1-[4-(2,3-dichlorophenyl)methyl]piperazine amide (wherein the amine was not methylated). The mixture was then stirred with polymer bound benzaldehyde resin and filtered, thereby removing the racemized O-(phenylmethyl)-L-tyrosine, 1-[4-(2,3-dichlorophenyl)methyl]piperazine amide. The filtrate was concentrated in vacuo and the residue was further purified by preparative HPLC to afford the racemic titled compound, bis trifluoroacetic acid salt (100 mg) as a colorless oil (HPLC purity:100%): MS Calcd for [C28H31Cl2N3O2+H]+: 512. found: 512.

Provenance & Evidence