Water → L-Pyroglutamyl-L-methionyl-L-alanyl-L-valyl-L-lysine

Participants

Reaction Steps

A sample of the protected 5-peptide XXIII (0.50 g, 0.55 mmole) was dissolved in DMF (60 ml), H2O (6 ml), DIEA (6 ml) and 10% Pd/BaSO4 (0.10 g) were added and the mixture hydrogenated for 8 hr. On tlc a single spot (RfC, 0.45; RfL, 0.75) was observed. The black solution was filtered on a layer of Celite, the latter washed with DMF and the filtrates evaporated in vacuo to dryness. The residue was dissolved in TFA (20 ml) containing acetyl-DL-methionine n-butyl ester (1.0 g) and kept at room temperature for 1/2 hr. The TFA was removed in vacuo and the residue dissolved in a mixture of EtOAc (20 ml) and H2O (20 ml). The aqueous layer was extracted twice with EtOAc (20 ml each), filtered and lyophilized to give a white powder, 0.40 g. In system C the spot remained near the origin; RfM, 0.45. Trace amounts of impurities, probably the pyroglutamyl derivative and the sulfonium salt could also be detected. A sample (0.10 g) was dissolved in AcOH (ca 2 ml) and heated to boiling for 3 min. After cooling the product was precipitated with ether (20 ml). The pyroglutamyl derivative was collected, washed with ether: 80 mg; m.p. 238°-242° C.; RfC, 0.10; RfM, 0.60. Glu, 0.98; Ala, 0.99; Val, 1.01; Met, 0.96.

Provenance & Evidence