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

Participants

Reaction Steps

The Boc group was removed from a sample (3.8 g, 6.6 mmole) of compound XX as described above. The partially deprotected 2-peptide ester (trifluoroacetate salt) was dissolved in DMF (60 ml) and treated with DIEA (2.4 ml, 15 mmole), HOBt (1.18 g, 7.7 mmole) and Boc-L-Ala-ONp (2.38 g, 7.7 mmole, Bachem) at 0°. After overnight storage at room temperature a semisolid mass formed. Most of the solvent was removed in vacuo, the residue triturated with EtOAc and with ether and dried: 3.6 g (85%), m.p. 140°-143° C.; [α]D23 -21.8° (c 0.8 DMF); RfB, 0.85; RfI, 0.62.

Provenance & Evidence