Isobutyl chloroformate → tert-butyl (2S)-2-(6-bromo-4-oxo-3,4-dihydrothieno[3,2-d]pyrimidin-2-yl)-3,6-dihydropyridine-1(2H)-carboxylate

Participants

Reaction Steps

To a mixture of (2S)-1-(tert-butoxycarbonyl)-1,2,3,6-tetrahydropyridine-2-carboxylic acid (1.16 g), triethylamine (1.42 mL) and tetrahydrofuran (12 mL) was added 2-methylpropyl chlorocarbonate (0.662 mL) with stirring at room temperature. After 1 hr, 3-amino-5-bromothiophene-2-carboxamide (752 mg) produced in Example 1, step D, was added, and the mixture was stirred in a microwave reactor at 100° C. for 2 hr. The reaction mixture was allowed to cool to room temperature, and poured into saturated aqueous sodium hydrogen carbonate. The mixture was extracted with ethyl acetate, and the extract was dried over anhydrous magnesium sulfate. Insoluble material was removed by filtration, and the filtrate was concentrated under reduced pressure. The residue was dissolved in ethanol (10 mL), 2M aqueous sodium hydroxide solution (10.2 mL) was added, and the mixture was stirred at 90° C. for 2 hr. The reaction mixture was ice-cooled, and 6M hydrochloric acid (3.33 mL) was added dropwise. The reaction mixture was poured into brine, and extracted with 3:1 ethyl acetate/tetrahydrofuran mixture. The extract was dried over anhydrous magnesium sulfate. Insoluble material was removed by filtration, and the filtrate was concentrated under reduced pressure. The residue was purified by basic silica gel column chromatography (ethyl acetate/hexane and methanol/ethyl acetate) to give the title compound (851 mg) as a white solid. The optical purity was 51.1% ee. The analysis was performed by high performance liquid chromatography (column: CHIRALPAK IC (4.6 mm i.d.×250 mm L, manufactured by DAICEL CHEMICAL INDUSTRIES, LTD.), mobile phase: hexane/ethanol (900/100), flow rate: 1 mL/min, column temperature: 30° C., detection 220 nm).

Provenance & Evidence