Dibenzo-18-crown-6 → 1alpha,3beta-dihydroxy-20(R)-{2(R)-hydroxy-3-methylbutyloxy}pregna-5,7,16-triene

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Reaction Steps

Using 1α,3β-bis(tert-butyldimethylsilyloxy)-20(R)-hydroxypregna-5,7,16-triene (69.7 mg, 0.125 mmol), potassium t-butoxide (170 mg, 1.52 mmol), dibenzo-18-crown-6 (22.0 mg, 0.0610 mmol), toluene (4 ml) and (R)-(−)-1,2-epoxy-3-methylbutane (0.13 ml, 1.24 mmol), alkylation reaction (109° C., 1 hour) and work up were performed by the same procedure as in Example 119, and then the residue was separated by preparative thin layer chromatography (0.5 mm×3, hexane:dichloromethane:ethyl acetate=45:5:2, developed three times) to give a fraction containing 1α,3β-bis(tert-butyldimethylsilyloxy)-20(R)-{2(R)-hydroxy-3-methylbutyloxy}pregna-5,7,16-triene (23.6 mg). An aliquot of 21.1 mg was deprotected with tetrahydrofuran (1 ml) and 1M tetra-n-butylammonium fluoride solution in tetrahydrofuran (0.2 ml) (reaction temperature 76° C., reaction period 13 hours) and worked up by the same procedure as in Example 119, and then the residue was purified by preparative thin layer chromatography (0.25 mm×1, dichloromethane:ethanol=15:1, developed twice) to give the title compound as a colorless oil (9.4 mg, 20%).

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