Chlorotrimethylsilane → 3-(3,5-Difluorophenyl)-2-((E)-hept-2-enoylamino)-propionic Acid

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Reaction Conditions

Reaction Steps

6.3 ml (49.7 mmol) of chlorotrimethylsilane are added to a solution of 5.0 g (24.9 mmol) of 3,5-difluoro-DL-phenylalanine in dichloromethane (150 ml) and the reaction mixture is heated to reflux for 1 h. After cooling to 0° C., 9.7 ml (55.9 mmol) of ethyldiisopropylamine are added slowly and then, dropwise, 3.64 g (24.9 mmol) of trans-2-heptenoyl chloride. The reaction mixture is stirred overnight with slow warming to RT and remains standing at RT for 2 days. For working up, it is evaporated to dryness in vacuo, the residue is taken up using diethyl ether and extracted with 2.5 pc. aqueous sodium hydrogencarbonate solution (250 ml). The aqueous phase is extracted twice with ether, and the combined organic phases are extracted a further three times with sodium hydrogencarbonate solution. The combined aqueous phases are brought to pH=2 using 1N aqueous hydrochloric acid and extracted three times with ethyl acetate. The combined ethyl acetate phases are dried over sodium sulfate, filtered, and the solvent is concentrated in vacuo. The residue is washed by stirring with diethyl ether and filtered. The filter residue is isolated, the filtrate is concentrated and again treated with diethyl ether. After repetition twice, a total of 6.12 g (79% of th.) of product are obtained as a colorless solid.

Provenance & Evidence