CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

4.18 (t, J = 3.4 Hz, 1H), 4.75-4.84 (m, 2H), 4.88-4.97 (m, 2H), 5.37-5.54 (m, 1H), 7.03-
7.17 (m, 7H), 7.25-7.43 (m, 9H), 7.55-7.65 (m, 2H), 7.74-7.78 (m, 2H); 13 C NMR: δ 10.6,
19.5, 27.1, 36.0, 38.9, 65.2, 74.2, 74.9, 117.3, 127.1, 128.3, 128.4, 128.6, 128.7, 129.7,
130.1, 132.9, 137.6, 139.9, 166.3. Anal. Calcd. for C 37 H 42 O 4 Si : C, 76.78; H, 7.31%.
Found: C, 75.98; H, 7.42%.
(4S,5S,6R,7R)-4-Benzoyloxy-5-methyl-6,7-isopropylidenedioxy-7-phenylhept-1-ene
143. As described earlier, treatment of 142 (0.150 g, 0.26 mmol) with Bu 4 NF (0.30 mL,
0.30 mmol, 1 M in THF) in THF (10 mL), work up of the reaction mixture, followed by
preparative thin layer chromatography (silica gel, 5% MeOH/CHCl 3 ) of the residue
furnished the pure desilylated product (0.071 g, 81%). This (0.21 mmol) on stirring with
PPTS (cat.) in dimethoxypropane (1 mL) for 1 h, followed by isolation and preparative
thin layer chromatography (silica gel; 10% EtOAc/hexane) afforded 143. Yield: 0.067 g
(84%); colourless oil; [α] 22 D + 11.2 (c 1.05, CHCl 3 ); IR: 2923, 1718 cm -1 ; 1 H NMR: δ 1.02
(d, J = 7.2 Hz, 3H), 1.28 (s, 3H), 1.35 (s, 3H), 1.82-1.89 (m, 1H), 2.15-2.26 (m, 2H), 4.15
(dd, J = 8.2, 3.6 Hz, 1H), 4.72-4.85 (m, 2H), 4.89-4.96 (m, 2H), 5.28-5.52 (m, 1H), 7.28-
7.48 (m, 8H), 7.95-8.10 (m, 2H); 13 C NMR: δ 10.2, 26.8, 27.0, 35.8, 40.1, 72.8, 79.5, 83.2,
108.6, 116.8, 127.2, 127.8, 128.5, 128.9, 133.0, 136.5, 168.1. Anal. Calcd. for C 24 H 28 O 4 :
C, 75.76; H, 7.42%. Found: C, 75.54; H, 7.35%.
(4S,5S,6R,7R)-6,7-Isopropylidenedioxy-5-methyl-7-phenylhept-1-en-4-ol 144.
Hydrolysis of 143 (0.060 g, 0.16 mmol) with K 2 CO 3 (0.048 g, 0.35 mmol) in MeOH (5
mL), usual work up and column chromatography (silica gel, 0-20% EtOAc/hexane)
furnished pure 144. Yield: 0.031 g (72%); colourless oil; [α] 22 D -3.36 (c 1.12, CHCl 3 )
(lit., 15b [α] 24 D -3.34 (2.21 in CHCl 3 )); IR: 3485, 2923 cm -1 ; 1 H NMR: δ 1.05 (d, J = 7.2
198