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18.1 18.2 l,l-Dimethylethyl (4i)-4-([(l,l-dimethylethyl)oxy]carbonyl}amino)-5-hydroxypentanoate: [00220] Triethylamine (11.49 mL, 82.4 mmol) and ethyl chloroformate (8.27 niL, 86.5 mmol) were added successively by syringe to 2V-t-BOC-D-glutamic acid 5-tert-bviotatyl ester (25 g, 82.4 mmol) in THF (588 mL) at <0 0C (ice-salt bath). After stirring in the cold bath for 40 min, solids were filtered and washed with THF (150 mL). The filtrate was transferred to a 250-mL addition funnel and added to a solution of sodium borohydride (8.42 g, 222.5 mmol) in H2O (114 mL) at 00C over 1 hour. The reaction mixture was maintained at 0 0C for 1.5 h and then stirred for 16 h (00C to room temperature). After the bulk of solvents were removed by rotary evaporation, the concentrate was quenched with ice water (50 mL) and 1 N HCl (50 mL). After extraction with EtOAc (4 x 100 mL), the extracts were washed with 100 mL: 0.5 M citric acid, saturated NaHCO3, H2O, and brine and concentrated in vacuo to give the title compound, which was used directly in the next step. ESMS [M+H]+ = 290.4, [2M+H]+ = 579.4. (Literature prep: J. Med. Chan, 1999, 42(1), 95-108 for other isomer).
With N-ethyl-N,N-diisopropylamine; In dichloromethane; at 20℃;
GENERAL PROCEDURE FOR THE COUPLING OF AMINES WITH CARBOXYLIC ACIDS: The compound is dissolved in an appropriate amount of dichloromethane and the carboxylic acid (1.1 equiv.) added followed by PS-CDI (2 equiv.) and DIEA (10 equiv.). The reaction is shaken at room temperature until the starting material has been consumed. Once complete, the reaction is filtered and the filtrate concentrated in vacuo to obtain the crude product. In most cases, the crude product is pure enough for further transformations. If the crude product is not sufficiently pure, it can be purified using normal or reverse phase chromatography.
(4R)-4-amino-5-{2-[({1-butyl-4-[([4-(trifluoromethoxy)phenyl]amino}carbonyl)amino]-1H-imidazol-2-yl}carbonyl)amino]ethoxy}-5-oxopentanoic acid hydrochloride[ No CAS ]
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