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

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Reaction Steps

Using 1α,3β-bis(tert-butyldimethylsilyloxy)-20(S)-hydroxypregna-5,7,16-triene (71.5 mg, 0.128 mmol), potassium t-butoxide (170 mg, 1.52 mmol), dibenzo-18-crown-6 (32.0 mg, 0.0888 mmol), toluene (4.5 ml) and (R)-(−)-1,2-epoxy-3-methylbutane (0.13 ml, 1.24 mmol), alkylation reaction (108° 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(S)-{2(R)-hydroxy-3-methylbutyloxy}pregna-5,7,16-triene (26.8 mg). This was deprotected with tetrahydrofuran (1 ml) and 1M tetra-n-butylammonium fluoride solution in tetrahydrofuran (0.4 ml) (reaction temperature 74° C., reaction period 12 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 (12.0 mg, 23%).

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