[CH3:1][C:2]1[CH:3]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:4]2([CH2:9][C:10](=[O:12])[CH:11]=1)[CH2:8][CH2:7][CH2:6][CH2:5]2.[Cl-].[Cl-].[Cl-].[Ce+3].[BH4-].[Na+].Cl>CO>[OH:12][C@H:10]1[CH2:9][C:4]2([CH2:5][CH2:6][CH2:7][CH2:8]2)[C@@H:3]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:2]([CH3:1])=[CH:11]1.[OH:12][C@@H:10]1[CH2:9][C:4]2([CH2:5][CH2:6][CH2:7][CH2:8]2)[C@@H:3]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:2]([CH3:1])=[CH:11]1A solution of ethyl 7-methyl-9-oxospiro[4.5]dec-7-ene-6-carboxylate (6.4 g, 27.3 mmol) in methanol (120 ml) was treated with anhydrous cerium trichloride (6.72 g, 27.3 mmol). The resulting mixture was stirred for 45 min., cooled to 0° C., and added within 40 min. to a mixture of sodium borohydride (0.75 g, 96%, 19.1 mmol) in methanol (60 ml) at 0° C. The resulting mixture was stirred for 2 h at 20° C., cooled to 0° C., treated with sodium borohydride (0.75 g, 96%, 19.1 mmol), stirred for 3 h at 20° C., cooled to 0° C., poured into 2N aqueous HCl and ice, and extracted three times with MTBE (200 ml). The combined organic phases were washed three times with a saturated aqueous solution of NaCl, dried (MgSO4) and concentrated. FC (SiO2, hexane/MTBE 3:1) of the crude product (7.6 g, cis/trans 19:81) gave cis-ethyl 9-hydroxy-7-methylspiro[4.5]dec-7-ene-6-carboxylate (0.82 g 13%), 29:71 cis-/trans-ethyl 9-hydroxy-7-methylspiro[4.5]dec-7-ene-6-carboxylate (0.71 g, 11%), and trans-ethyl 9-hydroxy-7-methylspiro[4.5]dec-7-ene-6-carboxylate (3.52 g, 54%).
読み込み中…
