L-Phenylalanine → L-Phenylalanine, N-[(1,1-dimethylethoxy)carbonyl]-L-leucyl-

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Reaction Conditions

Reaction Steps

H-Phe-OH (1.49 g, 9 mmol) fine powder was suspended in DMF (20 ml). After cooling at 0°, Et3N (1.26 ml, 9 mmol) was added, followed by Boc-Leu-pentafluorophenylester, i.e., Boc-Leu-OPfp (3.93 g, 9.9 mmol). It was stirred for 1 hr at 0° C and for 2.5 hr at room temperature. After filtration the solvent was evaporated and the residue was treated with H2O. The separated oil was extracted with EtOAc. The organic phase was washed with 10% citric acid, H2O, dried (Na2SO4) and evaporated to a smaller volume. Addition of petroleum ether and standing overnight in the refrigerator provided the product (XVI) which was recrystallized from EtOAc-petroleum ether to fine crystals, yield 2.3 g (67.6%); mp 104°-106° C; [α]D25 -3.40° (c 1, EtOH). Anal. Calcd for C20H30N2O5 (378.476): C, 63.47; H, 7.99; N, 7.40. Found: C, 63.46; H, 8.18; N, 7.49.

Provenance & Evidence