Triethylamine → Methyl 5-(dipropylamino)-4-((2-(1,3-dithiol-2-ylidene)-3-methoxy-3-oxopropanoyl)amino)-5-oxopentanoate

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Reaction Steps

2-((2-(1,3-Dithiol-2-ylidene)-3-methoxy-3-oxopropanoyl)amino)-5-methoxy-5-oxopentanoic acid (4) (239 g) was dissolved in dichloromethane (1.5 l), followed by the addition of 70.7 g of triethylamine. To the resulting solution, 71.8 g of ethyl chlorocarbonate were added dropwise at 5-10° C. under stirring over 30 minutes. Subsequent to further stirring at 15-20° C. for 3 hours, di-n-propylamine (70.7 g) was added dropwise at 5-10° C., followed by stirring at room temperature for 12 hours. The solvent was removed under reduced pressure, and ethyl acetate (2 l) was then added to the residue. The resulting precipitate was filtered off. After the ethyl acetate layer was washed with 0.5 N hydrochloric acid and then with water, the solvent was removed under reduced pressure. Diethyl ether (800 ml) was added to the residue and the resulting precipitate was collected by filtration, whereby methyl 5-(dipropylamino)-4-((2-(1,3-dithiol-2-ylidene)-3-methoxy-3-oxopropanoyl)amino)-5-oxopentanoate (5) (113 g, yield: 57%) was obtained as pale yellow crystals.

Provenance & Evidence