[C:1]([O:5][C:6]([N:8]1[CH2:16][CH2:15][CH:11]([C:12]([OH:14])=[O:13])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[CH2:17](O)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1.Cl.CN(C)CCCN=C=NCC>CN(C)C1C=CN=CC=1.ClCCl>[C:1]([O:5][C:6]([N:8]1[CH2:16][CH2:15][CH:11]([C:12]([O:14][CH2:17][C:18]2[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=2)=[O:13])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]A mixture of N-tert-butoxycarbonylisonipecotic acid (12.0 g, 52.3 mmol), benzyl alcohol (6.0 mL, 58 mmol), 1-(3-dimethylamino-propyl)-3-ethylcarbodiimide hydrochloride (11.04 g, 57.6 mmol), and 4-dimethylaminopyridine (642 mg, 5.25 mmol) in anhydrous dichloromethane (100 mL) was stirred at room temp. for 6 h. The resultant mixture was diluted with dichloromethane and washed successively with water, 10% aqueous citric acid, saturated sodium bicarbonate, and brine. The organic extract was dried over anhydrous magnesium sulfate, filtered, and concentration under vacuum. The residual oil was subjected to column chromatography on silica eluting with 20% ethyl acetate in hexane. Collection and concentration of appropriate fractions afforded the title product as white solid.
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