Into a 500 ml flask was placed 8.06 g of the subtitled compound of Example A, N-(Benzyloxycarbonyl)-3-(2-thienyl)-L-alanine, in 130 ml of THF. The compound was cooled to 0° C. N-Methylmorpholine (4.23 ml) was added, followed by isobutylchloroformate (4.04 ml) over two minutes. The mixture was stirred for 15-20 minutes, and 3.74 ml of t-butylamine was added. The bath was removed, and the mixture was stirred at room temperature for two hours. The mixture was concentrated on rotovap, and the residue was taken up in ethyl acetate. The residue was washed successively with H2O, HCl, and saturated NaHCO3 solution. The organics were separated and dried with Na2SO4, filtered, and concentrated to an oil. The oil was dissolved in 100 ml hexane and cooled in a refrigerator overnight to give a solid. The hexane was decanted, followed by drying to yield a solid of 9.25 g N-(carbobenzyloxy)-3-(2-thienyl)-L-alanine-tert-butylamide (97% yield).
