[CH3:1][C:2]1([CH3:18])[CH2:7][O:6][CH:5]([C:8]2[CH:13]=[CH:12][C:11]([O:14][CH3:15])=[CH:10][CH:9]=2)[O:4][C@H:3]1[CH2:16][OH:17].C(N(CC)CC)C.CS(C)=O>ClCCl>[CH3:15][O:14][C:11]1[CH:10]=[CH:9][C:8]([CH:5]2[O:4][C@@H:3]([CH:16]=[O:17])[C:2]([CH3:18])([CH3:1])[CH2:7][O:6]2)=[CH:13][CH:12]=1Following the general procedure for the oxidation reaction of Description 7, 23.0 g (91.2 mmol) of [(4R)-5,5-dimethyl-2-(4-methoxyphenyl)-1,3-dioxan-4-yl]methan-1-ol (8a) in 650 mL of dichloromethane (DCM) in the presence of 63.5 mL (46.1 g, 456 mmol) of triethylamine and 52.0 mL (57.3 g, 733 mmol) of dimethylsulfoxide (DMSO) was reacted with 43.5 g (274 mmol) of sulfur trioxide pyridine complex to afford 21.4 g (94% yield) of the crude title compound (8b) as a yellow oil. The crude material was of sufficient purity to be used in the next step without further isolation and purification. Rf=0.53 (MTBE/Hxn=1:2). 1H NMR (400 MHz, CHCl3): δ=1.03 (s, 3H), 1.26 (s, 3H), 3.67 (d, J=11.6 Hz, 1H), 3.72 (d, J=11.6 Hz, 1H), 3.83 (s, 3H), 3.95 (d, J=1.2 Hz, 1H), 5.51 (s, 1H), 6.90-6.96 (m, 2H), 7.46-7.51 (m, 2H), 9.65 (d, J=1.6 Hz, 1H) ppm. MS (ESI) m/z: 251.1 (M+H)+, 272.9 (M+Na)+. The analytical data for the compound was consistent with the proposed structure and with the data given in the literature (Blakemore, et al., J. Org. Chem. 2005, 70, 5449-5460; and Shiina, et al., Bull. Chem. Soc. Jpn. 2001, 74, 113-122). Similar yields were obtained using classical Swern-oxidation conditions.
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