A solution of 1,1'-carbonyldiimidazole (4.54 g, 0.028 mole) and N,N-diethylethylenediamine (2.90 g, 0.025 mole) in tetrahydrofuran was stirred for 1 hr at room temperature. A solution of N-(1-methylethyl)-5-(phenylsulfonyl)-1-pentanamine (6.74 g, 0.025 mole) in tetrahydrofuran (dried over 4 A molecular sieves) was added and the resulting solution was heated over night at gentle reflux. The reaction mixture was stripped to dryness and the residue dissolved in chloroform. The chloroform layer was extracted with water, dried (anhydrous sodium sulfate), filtered and the solvent removed to give a brown oil. The brown oil was subjected to flash column chromatography on Silica Gel using methanol for elution. Fractions of similar purity were combined, solvent removed, and the oil dried in vacuo at 60° C. overnight. This produced 7.00 g (66.6% yield) of brown oil.
