To a solution of (2S,3S,4S)-2,3-bis(2-methylallyloxy)pentane-1,4-diol (920 milligrams (mg), 3.77 mmol) and (S)-1-benzyl 2-methyl aziridine-1,2-dicarboxylate (0.739 mL, 3.74 mmol) in anhydrous chloroform (CHCl3; 5 mL) was added BF3-Et2O (26 microliters (μL) 0.55 mmol) at 0° C. and the solution was stirred at 0° C. for 3 h. The crude reaction mixture was concentrated and purified by flash chromatography (SiO2) to furnish (S)-methyl 2-(benzyloxycarbonylamino)-3-((2S,3S,4S)-4-hydroxy-2,3-bis(2-methylallyloxy)-pentyloxy)-propanoate as a colorless oil (620 mg, 35%) and (S)-methyl 2-(benzyloxycarbonylamino)-3-((2S,3S,4S)-5-hydroxy-3,4-bis(2-methylallyloxy)pentan-2-yloxy)propanoate as a colorless oil (300 mg, 17%).
