[C:1]1([OH:13])[CH:12]=[C:6]([CH2:7][CH2:8][CH2:9][CH2:10][CH3:11])[CH:5]=[C:3]([OH:4])[CH:2]=1.O.[C:15]1(O)([CH3:24])[CH2:20][CH2:19][CH:18]([C:21]([CH3:23])=[CH2:22])[CH:17]=[CH:16]1>ClCCl.[Cl-].[Zn+2].[Cl-]>[CH3:11][CH2:10][CH2:9][CH2:8][CH2:7][C:6]1[CH:12]=[C:1]([OH:13])[C:2]([C@@H:17]2[C@@H:18]([C:21]([CH3:23])=[CH2:22])[CH2:19][CH2:20][C:15]([CH3:24])=[CH:16]2)=[C:3]([OH:4])[CH:5]=1A mixture of olivetol (3.6 g, 20 mmol), zinc chloride (3.5 g, 26 mmol), water (3.5 mL, 19 mmol) and dichloromethane (35 mL) was refluxed for 1 hour. A solution of (−)-p-mentha-2,8-dien-1-ol (3.0 g, 20 mmol) in dichloromethane (10 mL) was added drop-wise over 0.75 hour to the refluxing mixture, and the resultant reaction mixture was mixed for 0.5 hours at reflux. The mixture was cooled to 25° C., ice water (50 mL) was added, and the resultant biphasic mixture stirred for 20 minutes at 0° C. The resultant organic phase was collected, washed with water (2×20 mL) and 5% NaHCO3 (20 mL). The organic phase was dried over Na2SO4, filtered, and concentrated under reduced pressure to provide 6.0 g of first crude (+)-CBD residue. Analysis (GC) of the first crude (+)-CBD residue indicated that it contained (+)-CBD (46.9%) and abn-(−)-CBD (19.7%). The first crude (+)-CBD residue was purified by column chromatography on silica gel (eluent MTBE/hexane) to provide 2.4 g of a second crude (+)-CBD residue.
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