To a stirred solution of 66.32C (0.850 g, 3 mmol) in THF (33 mL) at −78° C. was added tert-butyllithium (6 mL, 10 mmol, 1.7M). The reaction was stirred for 5 hours and then a saturated solution of ammonium chloride was added and the mixture was extracted three times with EtOAc. After drying over anhydrous magnesium sulfate and filtering, the organic solvent was removed under reduced pressure and the product was then purified on silica gel (0-40% EtOAc in hexanes) to yield 66.32D as a colorless oil (0.670 g, 72% yield).
