Triethylamine → (N-benzyloxycarbonyl-O-benzyl-L-tyrosyl)-D-alanine methyl ester

Participants

Reaction Conditions

Reaction Steps

Triethylamine (5.7 ml.), then isobutylchloroformate (5.3 ml.), were added with stirring to a solution of N-benzyloxycarbonyl-O-benzyl-L-tyrosine (16.68 g.) in acetone (175 ml.) maintained at -20° C. The solution was stirred for 10 minutes at -20° C., then D-alanine methyl ester hydrochloride (6.4 g.) and triethylamine (5.7 ml.) in chloroform (65 ml.) were added. Stirring was continued one hour at this temperature, then four hours at room temperature. The mixture was filtered and the filtrate was stripped of volatiles. The residue and the filtration solid were combined and distributed between water (200 ml.) and ethyl acetate (250 ml.). Part of the product was collected by filtration and washed with aqueous hydrochloric acid, water, saturated sodium bicarbonate and water. The ethyl acetate layer was washed with cold aqueous hydrochloric acid (0.5N), water, saturated aqueous sodium bicarbonate, water again and saturated aqueous sodium chloride and stripped of volatiles, yielding another part of the product. The two parts were combined and recrystallized from absolute ethanol, affording (N-benzyloxycarbonyl-O-benzyl-L-tyrosyl)-D-alanine methyl ester (15.28 g.; m.r. 161°-163° C.; [α]D25 -11.7°, c=2, dimethylformamide)

Provenance & Evidence