To a mixture of ethyl 2-(tert-butoxycarbonylamino)-4-methylthiazole-5-carboxylate (0.29 g, 1.00 mmol), (S)-(+)-2-amino-1-propanol (0.18 g, 1.00 mmol) and diphenyl-2-pyridinylphosphine (0.40 g, 1.50 mmol) in anhydrous tetrahydrofuran (20.0 mL) was added diethyl azodicarboxylate (0.26 g, 1.50 mmol) at 0° C. The resulting solution was stirred at ambient temperature for 0.5 h. Additional diphenyl-2-pyridinylphosphine (0.13 g, 0.50 mmol) and diethyl azodicarboxylate (0.096 g, 0.50 mmol) were added to the reaction mixture and stirred at ambient temperature for 4 h. The reaction mixture was diluted with ethyl acetate (80 mL) and washed with 25% aqueous ammonium chloride solution (3×20 mL). The organic layer was dried over anhydrous sodium sulphate and filtered. The filtrate was concentrated in vacuo and the residue was purified by column chromatography eluted with 15-45% ethyl acetate in hexanes to afford the title compound as a colorless oil (0.35 g, 78%): 1H NMR (300 MHz, CDCl3) δ 5.30 (s, 1H), 4.26 (q, J=7.1 Hz, 2H), 4.18-3.95 (m, 3H), 2.59 (s, 3H), 1.58 (s, 9H), 1.33-1.28 (m, 12H), 1.17 (d, J=6.3 Hz, 3H); MS (ES+) m/z 244 (M−2Boc+1).
