To 1-(benzo[d][1,3]dioxol-5-yl)cyclopropanecarboxylic acid (864 mg, 4.2 mmol) was slowly added SOCl2 (916 μL, 12.6 mmol) followed by DMF (3 drops). The reaction mixture was heated at 60° C. for 0.5 h. The excess SOCl2 was removed under vacuum. The acid chloride was then dissolved in anhydrous CH2Cl2 (6 mL) and was slowly added to a solution of (R)-N-((2-amino-4-methylthiazol-5-yl)(2-chlorophenyl)methyl)-2-methylpropane-2-sulfinamide (Isomer A) (1.35 g, 3.8 mmol) and Et3N (2.92 mL, 21.0 mmol) in anhydrous CH2Cl2 (18 mL). The reaction mixture was stirred at room temperature for 18 h, diluted with CH2Cl2 and washed with 1N HCl solution, saturated aqueous NaHCO3 solution and brine. The organic layer was dried over MgSO4 and concentrated to provide 1-(benzo[d][1,3]dioxol-5-yl)-N-(5-((2-chlorophenyl)((R)-1,1-dimethylethylsulfinamido)methyl)-4-methylthiazol-2-yl)cyclopropanecarboxamide (Isomer A) as an orange solid (1.54 g, 75%) that was used without further purification. HPLC ret. time 3.59 min, 10-99% CH3CN, 5 min run; ESI-MS 546.5 m/z (MH+).
