To an anhydrous THF (10 mL) solution of (R)-2-acetamido-3-methoxy-N-(4-iodobenzyl)propanamide (376 mg, 1.0 mmol), triethylamine (280 μL, 2.0 mmol), 3-methoxyprop-1-yne (125 μl, 1.5 mmol), dichlorobis(triphenylphosphine)-palladium (II) (70 mg, 0.1 mmol), and CuI (38 mg, 0.2 mmol) were sequentially added under Ar. The mixture was stirred at room temperature (4 h), and then Et2O (10 mL) added and the precipitate filtered through a Celite pad. The filtrate was concentrated in vacuo and the residue was purified by flash chromatography on silica gel with EtOAc/MeOH (9/1) as the eluant to obtain (R)-6 (260 mg, 82%) as a beige solid: Rf=0.27 (EtOAc); mp 141-142° C.; [α]27D=+ 4.4° (c 1, DMSO); IR (nujol) 3278, 3096, 1640, 1554, 1458, 1370, 1304, 1257, 1192, 1099, 966, 903, 810, 732 cm−1; 1H NMR (CDCl3) δ 2.02 (s, CH3CO), 3.37 (s, OCH3), 3.45-3.47 (m, CHH′ and OCH3), 3.78 (dd, J=4.2, 9.0 Hz, CHH′), 4.32 (s, C≡CCH2OCH3) 4.38-4.52 (m, CH2N), 4.54-4.61 (m, NC(H)CO), 6.52 (d, J=6.6 Hz, CHNH), 6.91-6.99 (br t, CH2NH), 7.19 (d, J=7.9 Hz, 2 ArH), 7.41 (d, J=7.9 Hz, 2 ArH); 13C NMR (CDCl3) δ 23.2 (CH3CO), 43.2 (CH2N), 52.5 (CHCH2), 57.7 (C≡CCH2OCH3), 59.1 (OCH3), 60.4 (C≡CCH2OCH3), 71.7 (CH2OCH3), 85.2 (C≡C), 86.0 (C≡C), 121.8, 127.3, 132.1, 138.4 (C6H4), 170.4 (2C(O)); HRMS (M+H+) (ESI+) 319.1652 [M+H+] (calcd for C17H22N2O4H+ 319.1658); Anal. Calcd. for C17H22N2O4.0.33H2O: C, 62.95; H, 7.04; N, 8.64. Found: C, 62.98; H, 6.78; N, 8.47.
