Diethyl Ether → Tert-butyl 2-hydroxy-2-methylcyclopentylcarbamate

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A 1.6 M ether solution of methyllithium (13.59 mL, 21.75 mmol) was added to a stirred suspension of tert-butyl 2-oxocyclopentylcarbamate (1.97 g, 9.89 mmol, from Step 2) and cerium(III) chloride (5.36 g, 21.75 mmol) in tetrahydrofuran (50 mL) at −78° C. under nitrogen. After 2.5 h at −78° C., the mixture was quenched with saturated ammonium chloride, allowed to warm to room temperature, and filtered through a short bed of Celite to remove insoluble cerium salt. The filter cake was rinsed with ethyl acetate. The filtrated was extracted with ethyl acetate three times. The combined ethyl acetate phase was washed with saturated ammonium chloride and brine respectively, dried (MgSO4), filtered and concentrated. Silica gel chromatography, eluting with 0 to 50% ethyl acetate in hexanes, gave tert-butyl 2-hydroxy-2-methylcyclopentylcarbamate as yellow solid (1.47 g, 82% yield). 1H NMR analysis indicated the presence of approximately a 3:1 diastereomeric mixture.

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