CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

(2R,3S,4S)-3-(tert)-Butyldiphenylsilyloxy-1,2-cyclohexylidenedioxy-4-methylhex-5-ene
128. To a solution of 69c (1.44 g, 6.37 mmol) and imidazole (0.828 g, 12.18 mmol) in
CH 2 Cl 2 (30 mL) was added TBDPSCl (2.51 g, 9.15 mmol), and the mixture stirred for 12 h
at room temp. After completion of the reaction (cf. TLC), it was poured into water (20 mL)
and extracted with CHCl 3 (15 mL). The organic extract was washed with water and brine,
dried, and concentrated in vacuo. The residue was purified by column chromatography
(silica gel, 0-5% EtOAc/hexane) to give pure 128. Yield: 2.75 g (93%); colourless oil;
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[α] D +31.8 (c 2.31, CHCl 3 ); IR: 1586, 998, 909 cm -1 ; 1 H NMR: δ 0.93 (d, J = 7.0 Hz, 3H),
1.05 (s, 9H), 1.23-1.51 (m, 10H), 2.28-2.37 (m, 1H), 3.70-3.86 (m, 3H), 4.01-4.10 (m, 1H),
4.96-5.01 (m, 2H), 5.81-5.98 (m, 1H), 7.22-7.26 (m, 6H), 7.68-7.77 (m, 4H); 13 C NMR: δ
14.2, 19.6, 23.9, 24.0, 25.3, 26.9, 27.2, 34.7, 36.2, 40.9, 66.6, 76.1, 77.8, 108.9, 114.7,
127.5, 127.6, 129.7, 129.8, 133.8, 133.9, 135.6, 136.2, 140.4. Anal. Calcd. for C 29 H 40 O 3 Si:
C, 74.95; H, 8.68%. Found: C, 75.10; H, 8.56%.
(2R,3S,4R)-3-(tert)-Butyldiphenylsilyloxy-4,5-cyclohexylidenedioxy-2-methylpentanal
129. Ozone was bubbled through a cooled (-78 °C) solution of 128 (2.55 g, 5.49 mmol) in
CH 2 Cl 2 (20 mL) till the solution turned blue. After 0.5 h, the excess O 3 was removed by
purging with N 2 (gas), the mixture treated with Ph 3 P (6.0 g, 22.89 mmol), and stirred for
16 h at room temperature. Most of solvent was removed in vacuo, the residue was
dissolved in hexane (30 mL) and chormatographed (silica gel, 0-10% EtOAc/hexane) to
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furnish pure 129. Yield: 2.08 g (81%); colourless oil; [α] D +8.2 (c 1.00, CHCl3 ); IR:
1726 cm -1 ; 1 H NMR: δ 1.01 (s, 9H), 1.16-1.28 (m containing a d at δ 1.26, J = 7.0 Hz, 5H),
1.41-1.48 (m, 8H), 2.68-2.71 (m, 1H), 3.42-3.48 (m, 1H), 3.74-3.81 (m, 1H), 4.12-4.22 (m,
2H), 7.32-7.42 (m, 6H), 7.56-7.71 (m, 4H), 9.55 (d, J = 1.2 Hz, 1H); 13 C NMR: δ 7.4,
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