N-(Triphenylmethyl)-L-asparagine → Z-Ala-Ala-Asn(Trt)-OH

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The tripeptide Z-Ala-Ala-Asn(Trt)-OH (2) was prepared according to the following procedure: To a stirred solution of H-Asn(Trt)-OH (4.97 g, 13.28 mmol, obtained from Bachem) in dry DMF (25 ml) a solution of Z-Ala-Ala-OSu (5.2 g, 13.28 mmol) in dry DMF (20 ml) was added and stirred for 14 h at room temperature. The solvent was evaporated in vacuo by using an oil pump. The obtained crude compound was dissolved in ethyl acetate (100 ml), washed with 1 N HCl (2×30 ml) and water (30 ml). The organic layer was dried over Na2SO4, filtered and concentrated under reduced pressure to give the tripeptide as a white solid (7.95 g, 92%) of m.p. 196° C. The peptide was used without further purification.—1H NMR (500 MHz, DMSO-d6): δ=1.18 (d, 3 H, J=7.1 Hz, CH3), 1.22 (d, 3 H, J=7.0 Hz, CH3), 2.62-2.88 (m, 2 H, CHCH2), 4.06-4.12 (m, 1 H, CH), 4.31-4.37 (m, 1 H, CH), 4.46-4.50 (m, 1 H, CH), 4.98-5.04 (m, 2 H, CH2O), 7.15-7.35 (m, 20 H, aryl-H). —MS(EI) m/z (%): 651 [M+H+], 673 [M+Na+], 689 [M+K+].

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