[CH3:1][C:2]1[C:10]2[C:9]([CH3:12])([CH3:11])[CH2:8][CH2:7][S:6][C:5]=2[S:4][CH:3]=1.O1CCCC1.C([Li])CCC.[C:23](=[O:25])=[O:24]>CCCCCC>[CH3:1][C:2]1[C:10]2[C:9]([CH3:12])([CH3:11])[CH2:8][CH2:7][S:6][C:5]=2[S:4][C:3]=1[C:23]([OH:25])=[O:24]8.20 g (0.041 mol) of the title compound of Step B was added to 200 mL of tetrahydrofuran under nitrogen. The solution was cooled to about -65° C. and 21 mL (0.053 mol) of 2.5M n-butyllithium was added dropwise while keeping the reaction temperature below -55° C. After stirring for 1 h, an excess of solid CO2 was added in portions and the mixture was allowed to warm to room temperature over 2 hr. The mixture was then diluted with 150 mL of hexane and the precipitate was collected by filtration. The precipitate was added to a mixture of 300 mL of water and 300 mL of methylene chloride, cooled to about 0° C., and then acidified to pH 1 with concentrated hydrochloric acid. The layers were separated and the aqueous layer was extracted with diethyl ether (2×300 mL). The combined organic layers were dried (MgSO4), filtered, and evaporated to dryness to yield 6.36 g of the title compound of Step C as a solid melting at 176°-178° C. 1H NMR (DMSO-d6): δ 1.3 (s,6H), 1.95 (m,2H), 2.6 (s,3H), 3.08 (m,2H), 12.7 (br s, 1H).
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