CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

mixture was concentrated in vacuo, the residue was taken in Et 2 O (10 mL), the organic
extract washed with H 2 O and brine, and dried. Removal of solvent in vacuo followed by
preparative thin layer chromatography of the residue (silica gel, 10% EtOAc/hexane)
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furnished pure 138a. Yield: 0.054 g (75%); colourless oil; [α] D +7.3 (c 2.3, CHCl3 ); IR:
3438, 2933, 2857 cm -1 ; 1 H NMR: δ 1.03 (d, J = 6.0 Hz, 3H), 1.29-1.63 (m, 10H), 2.34-2.37
(m, 1H), 2.39-2.42 (m, 2H), 3.02 (broad s, 2H), 3.37-3.42 (m, 1H), 3.49-3.65 (m, 1H),
3.79-3.83 (m, 1H), 3.91-3.98 (m, 1H), 4.05-4.12 (m, 1H), 4.99-5.07 (m, 2H), 5.70-5.84 (m,
1H); 13 C NMR: δ 11.4, 23.8, 23.9, 25.0, 35.2, 36.1, 38.0, 40.7, 65.9, 72.3, 76.9, 77.8,
110.0, 115.8, 139.4. Anal. Calcd. for C 15 H 26 O 4 : C, 66.64; H, 9.69%. Found: C, 66.42; H,
9.48%.
(2R,3R,4S,5S)-1,2-Cyclohexylidenedioxy-3,5-isopropanedioxy-4-methyloct-7-ene
138b. As described earlier, reaction of 138a (0.030 g, 0.111 mmol) with DMP (1 mL) in
the presence of PPTS (cat.) afforded 138b after work up, and column chromatography
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(silica gel; 0–10% EtOAc/hexane). Yield: 0.029 g (83%); colourless oil; [α] D +7.3 (c 2.32
in CHCl 3 ); IR: 2935, 2858, 1104 cm -1 ; 1 H NMR: δ 1.06 (d, J = 6.6 Hz, 3H), 1.30 (s, 6H),
1.33-1.59 (m, 10H), 1.88-2.09 (m, 2H), 2.21-2.39 (m, 1H), 3.13-3.19 (m, 1H), 3.56-3.68
(m, 1H), 3.74-3.78 (m, 1H), 3.95-4.05 (m, 2H), 4.97-5.09 (m, 2H), 5.71-5.95 (m, 1H); 13 C
NMR: δ 13.1, 23.5, 23.9, 24.0, 25.2, 25.3, 34.7, 34.8, 36.7, 42.0, 67.8, 70.9, 73.5, 77.9,
100.3, 109.6, 114.4, 140.8. Anal. Calcd. for C 18 H 30 O 4 : C, 69.64; H, 9.74%. Found: C,
69.72; H, 9.56%.
(4S,5S,6R,7R)-4-Benzoyloxy-6-(tert)-butyldiphenylsilyloxy-7,8-cyclohexylidenedioxy-
5-methyloct-1-ene 139. Reaction of 138 (0.120 g, 0.321 mmol) with TBDPSCl (0.149 g,
0.543 mmol) in the presence of imidazole (0.044 g, 0.641 mmol) in CH 2 Cl 2 (5 mL) and
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