CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

7.51 (m, 3H), 7.92-8.08 (m, 2H); 13 C NMR: δ 11.4, 23.7, 23.9, 25.1, 34.4, 34.9, 36.0, 38.9,
64.1, 71.7, 74.7, 109.4, 117.5, 128.3, 129.5, 130.5, 132.8, 134.2, 165.9. Anal. Calcd. for
C 22 H 30 O 5 : C, 70.56; H, 8.07%. Found: C, 70.35; H, 7.96%.
(2R,3R,4S,5S)-1,2-Cyclohexylidenedioxy-5-benzoyloxy-4-methyloct-7-en-3-ol 138.
Oxidation of 137 (0.350 g, 0.95 mmol) with PCC (0.334 g, 1.52 mmol) in CH 2 Cl 2 (20 mL),
followed by work-up furnished the 3-keto compound. In view of its instability it was
directly used for the next step. For this, K-selectride ® (1.31 mL, 1.31 mmol, 1 M in THF)
was injected into a cooled (-78 o C) and stirred solution of the above compound (0.290 g,
0.78 mmol) in THF (15 mL). After stirring the mixture at the same temperature till
completion of the reaction (cf. TLC, ~ 3 h), the excess hydride was decomposed with
MeOH, the supernatant decanted and concentrated in vacuo. The residue was taken in Et 2 O
(50 mL), the organic extract washed with H 2 O and brine, and dried. Removal of solvent in
vacuo followed by column chromatography of the residue (silica gel, 0-10%
22
EtOAc/hexane) furnished pure 138. Yield: 0.291 g (82%); colourless oil; [α] D +38.8 (c
1.06, CHCl 3 ); IR: 3477, 1724 cm -1 ; 1 H NMR: δ 1.03 (d, J = 7.2 Hz, 3H), 1.32-1.36 (m,
2H), 1.37-1.57 (m, 8H), 2.09-2.21 (m, 1H), 2.26-2.34 (m, 2H), 3.50-3.54 (m, 1H), 3.87-
3.94 (m, 2H), 4.13-4.18 (m, 1H), 4.34-4.45 (m, 1H), 5.03-5.12 (m, 2H), 5.25-5.32 (m, 1H),
5.78-5.93 (m, 1H), 7.39-7.53 (m, 3H), 7.99-8.06 (m, 2H); 13 C NMR: δ 15.0, 23.7, 23.8,
25.0, 34.7, 36.1, 40.6, 64.4, 73.8, 76.2, 79.1, 109.1, 114.9, 129.4, 130.3, 133.2, 136.7,
140.4, 167.7. Anal. Calcd. for C 22 H 30 O 5 : C, 70.56; H, 8.07%. Found: C, 70.71; H, 8.15%.
(2R,3R,4S,5S)-1,2-Cyclohexylidenedioxy-4-methyloct-7-en-3,5-diol 138a. A mixture of
138 (0.100 g, 0.267 mmol) and anhydrous K 2 CO 3 (0.062 g, 0.454 mmol) in MeOH (10
mL) was stirred at 0 o C. After consumption of the starting material (cf. TLC, ~2 h), the
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