Dicyclohexylcarbodiimide → 3-methoxy-5-(N-carbobenzyloxy-L-phenylalanyl-L-alaninamido)-[1,2,4]thiadiazole

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Reaction Steps

To a solution of 5-amino-3-methoxy-[1,2,4]thiadiazole (0.37 g, 2.8 mmol) and N-carbobenzyloxy-L-phenylalanyl-L-alanine, N-Cbz-Phe-Ala-OH, (1.0 g, 2.7 mmol) in DMF (25 mL) was added 1,3-dicyclohexylcarbodiimide, DCC, (0.56 g, 2.7 mmol). After stirring for 30 min, 1-hydroxybenzotriazole hydrate, HOBT, (0.36 g, 2.7 mmol) was added and the resulting mixture was stirred at room temperature for 20 h. Volatile materials were removed in vacuo and the residue was purified by column chromatography on silica gel using a solvent mixture of dichloromethane and methanol (96/4) thereby affording the title compound as a white solid (1.2 g). Further purification by cristallization and chromatography on silica gel gave 3-methoxy-5-(N-carbobenzyloxy-L-phenylalanyl-L-alaninamido]-[1,2,4]thiadiazole (0.87 g, 67% yield). M.p. 161-162° C.; 1H-NMR (CDCl3) δ7.14-7.38 (m, 12H, 10Ar-H and 2 NH), 5.92 (br. s, 1H, NH), 5.06 (s, 2H, OCH), 4.38 (m, 1H, CHCH2Ar), 4.00 (m, 1H, CHCH3), 3.97 (s, 3H, OMe), 3.00-3.08 (m, 2H, CHCH2Ar), 1.34 (d, J=8.9 Hz, 3H, Me); MS (m/z) 484 (M+ +1), 416, 361, 316, 285, 185, 132, 75. The latter compound was also prepared by using diphenylphosphoryl azide and triethylamine instead of DCC/HOBT in 27.7% yield.

Provenance & Evidence