0.01 mol of NaOH dissolved in a minimum of water is added to a solution of 0.01 mol of (4-(cycloheptylamino)pyrid-3-yl)sulfonamide in 80 ml of a water/acetone mixture (1:1). The mixture is stirred with a magnetic rod, and 0.015 mol of cyclohexylisothiocyanate is added. Stirring is continued, while the reaction is followed by TLC (silica gel 60F254; mobile phase: ethyl acetate 9, methanol 1, triethylamine 0.2). Gentle heating can accelerate the reaction. The mixture is evaporated under reduced pressure and the residue is taken up in 100 ml of 0.2N NaOH. Any insoluble material is filtered out and the solution is corrected to pH 6.5-7 and left to crystallize for 1 hour in the refrigerator. The precipitate collected is suspended in 100 ml of a water/acetone mixture (4:1) saturated with NaHCO3. The mixture is stirred for 1 hour and then filtered, and the filtrate, brought back to pH 6.5-7, is left to crystallize in the refrigerator. The crystals are collected, washed in cold water and dried under vacuum at normal temperature. Yield is around 50-60%. Melting point: 195°-197° C.
