Dibenzo-18-crown-6 → 1alpha,3beta-dihydroxy-20(R)-{2(S)-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 (79.0 mg, 0.141 mmol), potassium t-butoxide (190 mg, 1.69 mmol), dibenzo-18-crown-6(25.0 mg, 0.0694 mmol), toluene (4.5 ml) and (S)-(+)-1,2-epoxy-3-ethylbutane (0.15 ml, 1.43 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(R)-{2(S)-hydroxy-3-methylbutyloxy}pregna-5,7,16-triene (27.8 mg). This was deprotected with tetrahydrofuran (1 ml) and 1M tetra-n-butylammonium fluoride solution in tetrahydrofuran (0.25 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 (11.0 mg, 19%).

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