To a stirring solution of (±)-2-acetoxy-5-(p-toluenesulfonoxymethyl)-tetrahydrofuran (example 59) (1.63 g, 5.19 mmol) and triethyl phosphite (1.16 mL, 6.75 mmol) in methylene chloride (75 mL) at -35° C. was added titanium (IV) chloride (0.57 mL, 5.19 mmol) dropwise. The yellow solution was then stirred at -35° C. for 30 min and then at 0° C. for 30 min. Saturated NaHCO3 (75 mL) was then added to the reaction mixture and the suspension was then filtered through Celite. The mixture was then partitioned followed by extraction of the aqueous phase with methylene chloride (2×50 mL). The combined extracts were then washed with brine (100 mL), dried (MgSO4) and concentrated. The residue was then purified by chromatography eluting with 75% EtAc/hexanes→EtAc giving the title compound as 1:1 mixture of cis and trans isomers (1.42 g, 78%).
