反应详情

The ethereal diazoisobutane (6) was gradually added to a solution of Boc-dehydroalanine-p-nitrobenzyl ester (2) (967 mg, 3 mmol) in CH2Cl2 (15 ml) at -10° C. to -15° C. with stirring. After stirring for 1 hr at the same temperature, the solvent was evaporated in vacuo and the resulting residue was triturated with hexane and filtered by suction to give 1.2 g of p-nitrobenzyl p-nitrobenzyl 3-t-butoxycarbonylamino-5-isopropylpyrazoline-3-carboxylate (7) (98.4%) mp 78°-79° C. (dec.). Recrystallization from AcOEt-n hexane gave colorless prisms having mp 87°-89° C. (dec.); IR (KBr) 3390(NH), 1745(C=O), 1690(C=O), 1605 (N=N).NMR (CDCl3)δ: 8.2 and 7.5 (d, d, 4H, ArH), 6.2 (br s, 1H, NH); 5.30 (s, 2H, OCH2), 4.8-5.2 (m, 1H, CH--N=N), 1.5-2.3 (m, 3H, (CH3)2CH and CH2), 1.35 (s, 9H, Boc), 1.00-1.30 (m, 3H, CH3), 0.8-1.10 (m, 3H, CH3).

1. stirringAfter stirring for 1 hr at the same temperature
2. customthe solvent was evaporated in vacuo
3. customthe resulting residue was triturated with hexane
4. filtrationfiltered by suction