The compound prepared in Example 309 (0.613 g) was suspended in 1,2-dichloroethane (30 mL). 2,2-Dimethoxyacetaldehyde solution in water (60% by weight) (2.28 mL) and beaded molecular sieves were added and the reaction mixture stirred at room temperature for 4 hours. Sodium triacetoxyborohydride (2.62 g) was added and the reaction mixture stirred at room temperature overnight. The reaction mixture was diluted with ethyl acetate, washed with saturated aqueous sodium bicarbonate solution and brine. The organics were dried over magnesium sulfate, filtered and concentrated under reduced pressure to afford the crude material, which was purified by flash column chromatography (eluant: 2% (9:1 methanol/concentrated ammonium hydroxide)/dichloromethane) to furnish the title compound (0.555 g) with the following physical properties.
