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Intermediate 37 (2.02 g, 7.4 mmol) was dissolved in a mixture of dioxane/ H2O (16 ml/4 ml) and the mixture was cooled on an ice-bath. LiOH (355 mg, 14.8 mmol) was added and the resulting mixture was stirred for 20 h at r.t. The volatiles were evaporated under reduced pressure. The mixture was cooled using an ice-bath, and was acidified with an aq. IN HCl solution until pH 4. The precipitate was filtered off, washed with cold water (10 ml), and dried in vacuo. Yield 1.5 g of intermediate 39 (88 %).
Intermediate C3: 8-Bromoimidazori,2-alphalpyridine-2-carboxylic acidTo a solution of 2-amino-3-bromopyridine (7.4 g, 0.0428 mol) in dimethoxyethane (70 mL) under N2, ethylbromopyruvate (9.28 g, 0.0428 mol) was added, and the mixture stirred at RT for 18 hours. The resulting solids were filtered and washed with Et2O, then re-suspended in absolute EtOH (40 mL) and refluxed for 2 hours. The reaction was concentrated to remove EtOH, diluted with K2CO3(aq.) and extracted with DCM (2 x 100 mL). The DCM extracts were dried over Na2SO4, filtered and concentrated to give a foam (9.2 g). The EPO <DP n="53"/>foam was dissolved in THF (230 rnL) and treated with IN NaOH (170 mL, 0.170 mol) at 40C for 2 hours. The reaction was cooled to RT, diluted with IN HCl (170 mL, 0.170 mol) and concentrated to remove the THF (pH of mixture = 3.0). The mixture was cooled to 0C, aged for 30 minutes and filtered. The cake was washed with H2O (40 mL) and dried under vacuum to give 7.94 g. LRMS (M+H)+ 241.
A suspension of intermediate 39 (322 mg, 1.34 mmol) and carbonyldiimidazole (238 mg, 1.47 mmol) in THF (11 ml) was stirred at r.t. for 2 h. DIPEA (0.233 ml, 1.34 mmol) was added and the resulting mixture was stirred for 30 min. at r.t. Then DMF (2 ml) was added to the suspension and the mixture was stirred for 60 h at r.t. The r.m. was cooled to 0 0C and O,N-dimethyl-hydroxylamine (143 mg, 1.47 mmol) was added. The mixture was stirred for 20 h at r.t. The solvents were evaporated under reduced pressure. The residue was dissolved in DCM and washed 3 times with H2O. The organic layer was dried (MgSO4), filtered and evaporated under reduced pressure. The residue was purified via flash column chromatography over silicagel (eluent: DCM/MeOH(NH3) from 100/0 to 99/1). The product fractions were collected and the solvent was evaporated in vacuo. Yield: 216 mg of intermediate 42 (57 %).
SOCl2 (15 ml, 206 mmol) was added slowly to intermediate 39 (1.6 g, 6.6 mmol) while cooling on ice. The resulting solution was heated to reflux temperature for 4 h, and was then cooled to r.t. and concentrated in vacuo. The residue was triturated with DIPE and finally the product was dried. Yield: 1.7 g of intermediate 40 (99 %).
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