CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

As described earlier, compound 108 was reduced with LiAlH 4 (0.21 g, 5.4 mmol)
in dry THF (20 mL). Usual work-up followed by flash chromatography (silica gel, 0-20%
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EtOAc/hexane) gave pure 109. Yield: 0.21 g (65%); colourless oil; [α] D - 4.3 (c 0.8,
CHCl3); IR: 2957, 909 cm -1 ; 1 H NMR: δ 0.88 (t, J = 6.0 Hz, 6H), 1.17-1.38 (m, 14H),
1.98-2.06 (m, 1H), 4.89-5.02 (m, 2H), 5.71-5.91 (m, 1H); 13 C NMR: δ 14.0, 22.3, 22.6,
28.9, 29.1, 29.3, 29.5, 31.9, 33.8, 34.1, 114.0, 139.1. Anal. Calcd. for C 12 H 24 : C, 85.63 H,
14.37%. Found, C, 85.78; H, 14.29%.
(R)-2-propyloctanoic acid V : Ozone was bubbled through a cooled (-78 o C) solution of
109 (0.15 g, 0.89 mmol) and methanolic NaOH (1.0 mL, 2.5 M) in CH 2 Cl 2 (10 mL) for 20
min. After stirring for 3 h, the mixture was diluted with CHCl 3 and water, and brought to
room temperature. The organic layer was separated and the aqueous layer extracted with
CHCl 3 . The combined organic extracts were washed with water and brine, and dried.
Removal of solvent in vacuo afforded crude ester residue.
To a solution of the ester in MeOH (10 mL) was added a methanolic NaOH (5.0
mL, 2.0 M) and the solution stirred till the ester was completely consumed (cf. TLC). Fter
concentration under vacuum, the mixture was diluted with water and extracted with Et 2 O
(30 mL). The aqueous phase containing the sodium salt of the acid was separated, cooled
(0 o C) and acidified to pH 2 with aqueous HCl. The mixture was extracted with EtOAc (30
mL). The extract was dried and the solvent was removed to afford the pure acid V. Yield:
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0.12 g (71% in two steps); white solid; [α] D -5.7 (c 0.7, CH2 Cl 2 ); IR: 2986 (broad), 1714
cm -1 ; 1 H NMR: δ 0.89 (broad t, J = 6.8 Hz, 6H), 1.10-1.69 (m, 14H), 2.32-2.43 (m, 1H),
11.3 (broad s, 1H); Anal. Calcd. for C 11 H 22 O 2 : C, 70.92 H, 11.90%. Found, C, 70.79; H,
11.81%.
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