CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

36.1, 39.8, 65.9, 74.9, 76.7, 109.6, 116.3, 128.3, 129.6, 129.9, 132.9, 138.4, 165.8. Anal.
Calcd. for C 20 H 26 O 4 : C, 72.70; H, 7.93%. Found: C, 72.72; H, 8.12%.
(2R,3S,4S)-3-Benzoyloxy-4-methyl-5-hexene-1,2-diol 72. To a cooled (0 o C) and stirred
solution of 71 (1.4 g, 4.24 mmol) in CH 2 Cl 2 (25 mL) was added aqueous TFA (10 mL) in
portions. When the reaction was complete (after ~2.5 h, cf. TLC), the mixture was treated
with NaHCO 3 , and water, and the mixture extracted with CHCl 3 (20 mL). The combined
organic extracts were washed with water (20 mL) and brine (5 mL), and dried. Removal of
solvent in vacuo followed by column chromatography (silica gel, 5% CHCl 3 /MeOH) of the
residue afforded 72. Yield: 0.92 g (86%); colourless thick oil; [α] 24 D +7.5 (c 1.04, CHCl 3 );
IR: 3411, 1724, 995, 920 cm -1 ; 1 H NMR: δ 0.98 (d, J = 7.0 Hz, 3H), 2.86-2.96 (m, 3H),
3.56-3.71 (m, 2H), 3.76-3.84 (m, 1H), 5.01 (dd, J = 2.8 and 8.6 Hz, 1H), 5.13-5.25 (m,
2H), 5.77-5.88 (m, 1H), 7.40-7.58 (m, 3H), 7.99-8.04 (m, 2H); 13 C NMR: δ 17.4, 38.5,
62.6, 70.7, 76.7, 116.8, 128.5, 129.3, 129.8, 133.5, 138.1, 167.2. Anal. Calcd. for
C 14 H 18 O 4 : C, 67.18; H, 7.25%. Found: C, 67.32; H, 7.09%.
(3S,4R,5R)-4-Benzoyloxy-6-(tert)-butyldiphenylsilyloxy-3-methyl-1-hexene 73. A
cooled (0 o C) solution of 72 (0.8 g, 3.2 mmol), TBDPSCl (0.89 g, 3.2 mmol) and imidazole
(0.26 g, 3.82 mmol) in CH 2 Cl 2 (20 mL) was stirred for 4 h. Water was added to the
mixture, which was extracted with CHCl 3 (20 mL). The combined organic extracts were
washed with water (20 mL) and brine (5 mL), dried and concentrated in vacuo. The residue
was subjected to column chromatography (silica gel, 5-15% EtOAc/hexane) to afford 73.
24
Yield: 1.25 g (80%); colourless oil; [α] D +7.9 (c 0.971, CHCl3 ); IR: 3450, 1726, 997, 924
cm -1 ; 1 H NMR: δ 1.01 (d, J = 6.8 Hz, 3H), 1.09 (s, 9H), 1.12 (broad s, 1H), 2.66-2.70 (m,
1H), 3.00-3.35 (m, 2H), 3.81-4.12 (m, 1H), 5.03 (dd, J = 2.4 and 7.8 Hz, 1H), 5.21-5.29
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