Dimethyl Sulfate → HCID 11809660, compound

Participants

Reaction Steps

Protected amino acid I was prepared from D-tyrosine in five steps. First, D-tyrosine was chlorinated with sulfuryl chloride in glacial acetic acid (R. Zeynek, Hoppe-Seyler's Z. f. Physiol. Chemie 1926, 144, 247-254). Next N-(tert-butoxycarbonyl)-3-(3-chloro-4-hydroxyphenyl)-D-a lanine was obtained in 94% yield by treating a suspension of the amino acid in 50% aqueous dioxane with di-tert-butyldicarbonate in the presence of triethylamine. The resulting product was dimethylated with dimethyl sulfate in the presence of potassium carbonate in refluxing acetone in 84% yield. The methyl ester was then saponified with sodium hydroxide in aqueous dioxane to yield N-(tert-butoxycarbonyl)-3-(3-chloro-4-methoxyphenyl)-D-a lanine in 86% yield. Exposure of the BOC-protected amino acid to trichloroethanol, pyridine and DCC in dichloromethane led to trichloroethyl ester I in 65% yield. Treatment of this material with trifluoroacetic acid led to a quantitative yield of the trifluoroacetate salt of I.

Provenance & Evidence