1-Hydroxybenzotriazole → t-Butyloxycarbonyl-L-glutaminyl-L-methionyl-L-alanyl-L-valyl-Nepsilon-benzyloxycarbonyl-L-lysine benzyl ester

Beteiligte Stoffe

Reaktionsschritte

The Boc group was removed from a sample of compound XXII (2.5 g, 3.3 mmole) as described in previous paragraphs. The trifluoroacetate salt washed with ether and dried; the white solid (RfC, 0.76) showed on tlc a slight impurity at the origin (presumably the t-butylsulfonium salt). This material was acylated with Boc-L-Gln-ONp (1.4 g, 3.8 mmole, Bachem) in the presence of DIEA (1.3 ml, 8 mmole) and HOBt (0.58 ml, 3.8 mmole). Next day the product was isolated as described for XII and then purified by precipitation from a solution in DMF with H2O. The product was washed with H2O and dried: 28 g (93%), m.p. 238°-241° C. [α]D23 -27.7° (c 0.8, DMF); RfK, 0.43; RfL, 0.50.

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