O-(2,4,6-Trimethylbenzenesulfonyl)hydroxylamine → 1-amino-3-(N-(2-hydroxyethyl)methylsulfonamido)-4-(3-(2-phenylpropan-2-ylcarbamoyl)phenyl)pyridinium 2,4,6-trimethylbenzenesulfonate

Participants

Reaction Conditions

Reaction Steps

To a cooled solution (0° C., ice bath) containing 3-(3-(N-(2-(tert-butyldimethylsilyloxy)ethyl)methylsulfonamido)pyridin-4-yl)-N-(2-phenylpropan-2-yl)benzamide (0.090 g, 0.12 mmol) and dichloromethane (2 mL) was added O-(mesitylsulfonyl)hydroxylamine (0.080 g, 0.37 mmol) in dichloromethane (2 mL) quickly, dropwise. The solution was maintained at 0° C. for 15 min, removed from the cooling bath and maintained at ambient temperature for 2 h. The solution was concentrated, dissolved in methanol (5 mL) and re-concentrated to afford 1-amino-3-(N-(2-hydroxyethyl)methylsulfonamido)-4-(3-(2-phenylpropan-2-ylcarbamoyl)phenyl)pyridinium 2,4,6-trimethylbenzenesulfonate as a light yellow foam (470, MH+). The product thus obtained was dissolved in DMF (2.4 mL) and added slowly dropwise over 20 min to a cooled mixture (0° C., ice bath) containing potassium carbonate (0.070 g, 0.50 mmol), methyl 3-(4-fluorophenyl)propiolate (0.030 g, 0.19 mmol) and DMF (2.0 mL). The mixture was kept in the cooling bath with stirring and allowed to proceed for 15 h at ambient temperature. The mixture was filtered and concentrated. Purification on silica gel (0-100% ethyl acetate/hexanes, 60 min gradient) afforded methyl 2-(4-fluorophenyl)-6-(N-(2-hydroxyethyl)methylsulfonamido)-5-(3-(2-phenylpropan-2-ylcarbamoyl)phenyl)pyrazolo[1,5-a]pyridine-3-carboxylate as a yellow residue. 1H NMR (500 MHz, CHLOROFORM-D) δ ppm 8.72 (s, 1H), 8.24 (s, 1H), 8.16 (s, 1H), 7.97-8.00 (m, 1H), 7.89 (t, J=7.93 Hz, 1H), 7.77-7.84 (m, 2H), 7.50-7.59 (m, 2H), 7.40-7.49 (m, 3H), 7.23-7.33 (m, 3H), 7.12-7.19 (m, 3H), 3.83 (s, 3H), 3.62-3.71 (m, 1H), 3.39-3.46 (m, 1H), 3.30-3.39 (m, 1H), 3.18-3.23 (m, 3H), 2.63-2.72 (m, 1H), 1.78 (t, J=12.21 Hz, 6H). LCMS: retention time: 2.403 min. LC data was recorded on a Shimadzu LC-10AS liquid chromatograph equipped with a Waters-Sunfire, 5 u, C18, 4.6×50 mm column using a SPD-10AV UV-Vis detector at a detector wave length of 220 nM. The elution conditions employed a flow rate of 4 mL/min, a gradient of 100% solvent A/0% solvent B to 0% solvent A/100% solvent B, a gradient time of 3 min, a hold time of 1 min, and an analysis time of 4 min where solvent A was 10% CH3CN/90% H2O/10 mM TFA and solvent B was 10% H2O/90% CH3CN/10 mM TFA. MS data was determined using a Micromass Platform for LC in electrospray mode. m/z 645 (MH+).

Provenance & Evidence