Trifluoroacetic acid → HCID 53706041, compound

Participants

Reaction Steps

Nα -t-Butoxycarbonyl-O-benzyl-L-seryl-O-benzyl-L-tyrosyl-D-alanyl-L-leucine methyl ester is prepared by deprotecting 11.4 g. (20 mmol) of Nα -t-butoxycarbonyl-O-benzyl-L-tyrosyl-D-alanyl-L-leucine methyl ester with 50 ml. of trifluoroacetic acid in 40 ml. of dichloromethane at 20° C. for 12 minutes. The mixture is evaporated to dryness at 40° C. under reduced pressure and the residue twice taken into dichloromethane and evaporated to dryness followed by drying under high vacuum for 2 hours. The oily product is dissolved in 70 ml. of dimethylformamide and treated at 10° C. with 10 ml. of triethylamine so that a pH of 7 is obtained. Additional triethylamine, 2.8 ml. (20 mmol) is added, followed by 6 g. (20 mmol) of Nα -t-butoxycarbonyl-O-benzyl-L-serine, 2.7 g (20 mmol) of 1-hydroxybenztriazole and (at -5° C.) 4.4. g. of dicyclohexylcarbodiimide. The mixture is slowly stirred to room temperature for two days. The mixture is filtered and the filtrate evaporated at 50° C. under reduced pressure. The residue is dissolved in dichloromethane and filtered. The solution is evaporated to yield an oil which crystallizes from dichloromethane and ether; 10.7 g.; m.p. 67°-71° C.

Provenance & Evidence