[Cl:1][C:2]1[CH:3]=[C:4]2[C:9](=[C:10]([C:12]([O-])=[O:13])[CH:11]=1)[O:8][C:7]([CH3:16])([CH3:15])[CH2:6][CH2:5]2.CC(C[AlH]CC(C)C)C.[OH-].[Na+].CC(OI1(OC(C)=O)(OC(C)=O)OC(=O)C2C=CC=CC1=2)=O>ClCCl.O>[Cl:1][C:2]1[CH:3]=[C:4]2[C:9](=[C:10]([CH:12]=[O:13])[CH:11]=1)[O:8][C:7]([CH3:16])([CH3:15])[CH2:6][CH2:5]26-Chloro-2,2-dimethyl-3,4-dihydro-2H-chromene-8-carboxylate (350 mg, 1.37 mmol) was dissolved in dichloromethane (6.87 mL) and cooled to −78° C. DIBAL-H (4.12 mL, 4.12 mmol) was added dropwise. The reaction mixture was warmed to room temperature and stirred for 1 hour. It was then cooled to 0° C., diluted with dichloromethane (10.0 mL) and water (2.00 mL) was added slowly, followed by a 15% aqueous NaOH solution (5.00 mL). The mixture was warmed to room temperature and stirred for 15 minutes. The organic layer was separated, dried over Na2SO4, filtered, and concentrated under vacuum. The crude alcohol was used directly in the next step without further purification. The crude alcohol was dissolved in dichloromethane (7.00 mL), and Dess-Martin periodinane (1.20 g, 2.75 mmol) was added in one portion at room temperature. The reaction mixture was stirred at room temperature for 30 minutes and then concentrated under vacuum on silica gel. It was then purified by silica gel chromatography eluting with 0-15% EtOAc/hexanes to give the desired product as a white solid.
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