tert-Butyl 1-benzyl-2-oxo-2-[(3-Pyridinylsulfonyl)amino]ethylcarbamate
1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (939 mg, 4.9 mmol), 1-hydroxybenzotriazole hydrate (562 mg, 4.15 mmol), and N-methylmorpholine (952 mg, 9.42 mmol) were added to an ice-cold solution of N-tert-butoxycarbonyl-L-phenylalanine (1.0 g, 3.77 mmol) in dichloromethane (20 ml), and the mixture stirred for 15 minutes. 3-Pyridinesulphonamide (Mon. für Chemie; 72; 77; 1938) (596 mg, 3.77 mmol) was added, and the reaction stirred at room temperature for 24 hours. The mixture was evaporated under reduced pressure and the residue partitioned between ethyl acetate (50 ml) and water (50 ml), and the layers separated. The aqueous layer was extracted with ethyl acetate, then dichloromethane, the combined organic extracts dried (MgSO4) and evaporated under reduced pressure. The crude product was purified twice by column chromatography on silica gel, using an elution gradient of ethyl acetate:ethanol (100:0 to 90:10) to give the desired product as a white foam, 1.01 g, 66;
1H NMR (DMSOd6, 300 MHz) δ: 1.30 (s, 9H), 2.77 (m, 1H), 2.97 (m, 1H), 3.84 (m, 1H), 5.95 (bs, 1H), 6.96 (m, 2H), 7.08 (m, 3H), 7.42 (m, 1H), 8.05 (d, 1H), 8.60 (d, 1H), 8.84 (m, 1H); [α]D=−10° (0.1% solution in methanol).
