Step C: and sodium borohydride (690 mg, 18.3 mmol) were added and the reaction was stirred for 0.5 hrs. The reaction was brought to -20 °C and quenched with saturated ammonium chloride solution (10 mL). The reaction was diluted with ethyl acetate (20 mL). The organics were separated and the aqueous further extracted with ethyl acetate (2 x 20 mL).