Reaction Steps
Oxygen was bubbled through a solution of the α-benzoate 3b (690 mg, 2.70 mmol) and DBPO (8.5 mg, 0.036 mmol) in hexane-benzene (50 mL, 7:3) with simultaneous addition (syringe pump) of a solution of PhSH (99 mg, 2.0 mmol) in hexane (20 mL) during 10 h. After completion of the thiol addition, the mixture was kept under oxygen for an additional 14 h, cooled to 4° C., and Ph3P (236 mg, 0.90 mmol) was added. The reaction mixture was stirred for 2 h at 5° C. and at rt for additional 1 h. The solvents were then evaporated, and flash chromatography (hexane-EtOAc, 9:1→1:1) afforded a mixture of diastereomeric (1S,4S,5S,7R,8S)-7-benzoyloxy-4,8-dimethyl-4-phenylthiomethyl-2,3-dioxabicyclo[3.3.1]nonan-8-ol 6a and (1S,4R,5S,7R,8R)-7-benzoyloxy-4,8-dimethyl-4-phenylthiomethyl-2,3-dioxabicyclo[3.3.1]nonan-8-ol 6b (24 mg of ca. 94% purity, 6% yield, 6a/6b ca. 65:35), Rf 0.42 (EtOAc-heaxane, 35:65) as a pale yellow oil. 1H NMR (400 ) MHz, CDCl3, δ): 1.23 (br. s, Me11, 6a), 1.59 (br. s, Me11, 6b), total 3 H; 1.41 (s, Me10, 6b), 1.42 (s, Me10, 6a), total 3 H; 1.91-2.37 (m, total 5 H, H35 +Ha,e6 +Ha,e9, 6a+6b); 3.00 (d, 2J=12.1 Hz, H12, 6b), 3.14 (br. d, 2J=12.1 Hz, H'12, 6b), 3.39 (d, 2J=12.8 Hz, H12, 6a), 3.80 (br. d, 2J=12.8 Hz, H'12, 6a), total 2 H; 3.82 (m, He1, 6a), 3.88 (dd, 3J1e9e =4.1 Hz, 3J1e9a =1.5 Hz, He1, 6b), total 1 H; 5.26 (dd, 1 H, 3J7e6e =5.0 Hz, 3J7e6a =1.7 Hz, He7, 6b), 5.27 (dd, 1 H, 1J7e6e =5.0 Hz, 3J7e6a =1.5 Hz, He7, 6a), total 1 H; 7.09 (m, 1 H), 7.22 (m, 6 b), 7.29 (m, 6a), total 2 H; 7.41-7.47 (m,), 7.54-7.58 (m,), total 5 H; 8.13 (m, 2 H), 13C NMR (100 MHz, CDCl3, δ): Isomer 6a: 22.30 (Me11), 23.42 (C9H2), 23.47 (Me10), 28.81 (C6H2), 29.36 (C5H), 40.78 (C12H2), 73.83 (C8), 74.36 (C7H), 80.85 (C1H), 82.74 (C4), 126.36 (C16H), 128.48 (2CH), 129.00 (2CH), 129.81 (2CH), 129.90 (2CH), 130.15 (C1-benz.), 133.11 (Cp-benz. H), 136.71 (C13), 166.33 (C=O); Isomer 6b: 21.68 (Me11), 23.35 (Me10), 23.56 (C9H2), 28.68 (C6H2), 30.86 (C5H), 40.37 (C12H2), 73.68 (C8), 74.51 (C7H), 81.38 (C1H), 82,83 (C4), 126.12 (C16H), 128.52 (2CH), 128.88 (2CH), 129.06 (2CH), 129.81 (C1-benz.), 129.90 (2CH), 133.18 (Cp-benz. H), 136.25 (C13), 166.25 (C=O).
