目前，在药物化学中用的最多的还是EDCI，其一个主要的特点就是其反应后的生成的脲是水溶性的，很容易被洗掉，一般EDCI与HOBt合用（注意: 这一反应HOBt一般是缺不了的，否则有可能导致缩合产率太低）。有时如果酸的a-位位阻大或者连有吸电子基团，反应会停留在活性酯这一步（这一活性酯的质谱信号较强，可通过MS或LC-MS检测到）。由于HOBt也是水溶性的，其使得反应的处理和纯化相对要容易。一般在这一缩合中要加入碱，特别当用胺或氨基酸的盐酸盐等缩合，常用的是加2-3当量的N-甲基吗啡啉或二异丙基乙胺（DIEA,Hunig base）, 缩合时以二氯甲烷为溶剂，若底物的溶解度不好，可用DMF作反应溶剂，再使用该方法进行。
To a solution of compound 11 (4.06 g, 10 mmol) in DMF (150 mL) wasadded N-hydroxybenzotriazole (HOBt, 5.64 g, 42 mmol), followed by dicyclohexylcarbodiimide (DCC; 8.60 g, 42 mmol). After stirring for l h,a solution of di-tert-butyl 4-amino-4-[2-(tert-butoxycarbonyl)ethyl]heptanedioate5 (17.34 g, 41.7 mmol)in DMF (60 mL) was added and the solution stirred at 25℃ for 23 h. The crystals were filtered and washed on thefilter with DMF (25 mL). The solvent wasdistilled at 50℃/1mm, and the residual oil was dissolved in ether (600mL). Crystals were filtered, the ethereal solutionwas washed successively with 10% HCl (2 x100 mL), saturated NaHCO3(2 x 100 mL), and brine (2 x 50 mL), then dried (Na2SO4). The ether solution was filtered throughcelite and solvent was then removed in vacuo to afford 19.0 g of crude product, which waspurified on a silica column eluting with toluene/EtOAc (1:1) to furnish (60%)the white, non-crystalline ester 12:14.0 g; mp 55-60℃. 1HNMR δ 1.43 (s, CH3, 108H), 1.94-2.28 (m, CH2CH2,64H), 5.87 (s, NH, 4H), 6.17 (s, CH=CH, 2H); 13C NMR (DMSO-d6) δ28.3 (CH3), 29.3 (CH2CH2),56.8 (CNH), 69.0 (CSO2), 171.1 (CO), 171.4 (CO).
To a solution of amine 13 (106 mg, 0.3 mmol),Fmoc-Phe-OH (116 mg, 0.3 mmol), and HOBt (44.8 mg, 0.33 mmol) in anhydrous DMF(2 mL) was added DIC (56 µL, 0.36 mmol). The resulting mixture was stirred at roomtemperature overnight, and DMF was then evaporated under high vacuum. The residue was dissolved in ethyl acetate (10mL), washed sequentially with saturated aqueous NaHCO3 and brine,and then dried over Na2SO4. The evaporation of the solvent gave the crudeproduct that was directly submitted for the Fmoc removal without purification. The crude product was dissolved in DMF (8 mL),piperidine (2.0 mL) was added, and the resulting solution was stirred at roomtemperature for 1 h. Following thesolvent evaporation, the residue was purified by silica gel chromatography (50%ethyl acetate in hexanes to 10% methanol in chloroform) to provide product 14(128 mg) in 85% yield as a mixture of two diastereomers. 1H NMR (CDCl3, 400MHz) ‰ 8.12-8.00 (2H, m), 7.90-7.80 (2H, m), 7.70-7.54 (2H, m), 7.42(2H, m), 7.35-7.20 (2H, m), 6.97-6.83 (3H, m), 5.32 (1H, m), 4.32 (1H, m),4.20-4.03 (2H, m), 3.96-3.80 (2H, m), 3.60 (1H, m), 2.98 (3H, m), 2.88 (2H, s),2.60 (1H, s), 2.00 (1H, m), 1.85 (2H, m), 1.77-1.55 (3H, m); MS (ES+) m/z) 501.4 (M + 1).
To a solution of amine16 (0.284 mg, 1.19 mmol) and 5-hexenoic acid 15(0.136 g,1.19 mmol) in CH2Cl2 (12.0 ml) at 0℃were added HOBt (0.177 g,1.31 mmol) and EDC (0.251 g,1.31 mmol). The reaction mixture was stirredat room temperature for 10 h, then washed with 5% aqueous HCl (3×15.0 ml), 5% aqueous NaHCO3 (20 .0 ml),H2O (20.0 ml), and brine (20.0 ml), and dried (Na2SO4). Purification by flash chromatography(CH3Cl/MeOH, 10%, Rf = 0.43) afforded amidoalkene 17 in 99%yield as a brown oil.
A DMF solution (10 mL) containing HOBt (103 mg, 0.76mmol), EDC (192 mg, 1.0 mmol), and Boc-D-Ile (172 mg, 0.76 mmol) was stirred atroom temperature for 20 h. A solution ofthe amino ketal 18 (0.41 g,0.76 mmol) and 4-methylmorpholine (0.17 mL, 1.5 mmol) dissolved in 10 mL of DMFwas then added to the reaction mixture. After4 h the reaction mixture was partitioned between EtOAc and H2O. The organic layer was washed with H2O,dried over MgSO4, and concentrated under reduced pressure. Flash chromatography (4:1 EtOAc/hexanes)afforded the Boc ketal 19 (0.44 g,0.59 mmol, 78%).