To a stirred solution of (3R,4S,5R,6R)-3,4,5-tris(benzyloxy)-6-(benzyloxymethyl)-2-(4-chloro-3-(4-vinylbenzyl)phenyl)tetrahydro-2H-pyran-2-ol (intermediate AN) (350 mg) in 4 mL of CH2Cl2:CH3CN (1:1) at −15° C. was added Et3SiH (0.146 mL), followed by BF3.Et2O (0.09 mL). During the period of addition, the temperature was maintained at approximately −5° C. to −10° C. The stirred solution was allowed to warm to 0° C. over 5 h. The reaction was monitored by TLC, and after the starting material was consumed, the reaction was quenched by addition of saturated aqueous NaHCO3. The solvent was removed under reduced pressure. The residue was then dissolved in a mixture of 40 mL of ethyl acetate and water (1:1). After separation of the organic layer, the aqueous phase was extracted 2× with 20 mL of ethyl acetate. The organic phases were combined and washed with brine and water before drying over Na2SO4. Concentration of the solution yielded a yellow gel, which was purified by preparative TLC to obtain pure intermediate AO (100 mg).
