C([Li])CCC.C(OP([CH2:14][C:15]([OH:17])=[O:16])(OCC)=O)C.[CH3:18]/[C:19](/[CH:27]=O)=[CH:20]\[C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1.Cl>O1CCCC1>[CH3:18][C:19](=[CH:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1)[CH:27]=[CH:14][C:15]([OH:17])=[O:16]Butyllithium (135 mL of 2.5 N solution) was added to 600 mL of anhydrous tetrahydrofuran (THF) at −65° C. A solution of diethylphosphonoacetic acid (30.5 g) in 220 mL of anhydrous THF was added dropwise to the stirred solution at −65° C. over a period of 60 minutes. The resulting solution was stirred at −65° C. for an additional 30 minutes and then a solution of α-methyl-trans-cinnamaldehyde (23.2 g) in 100 mL of anhydrous THF was added to the reaction at −65° C. over a period of 70 minutes. The reaction was stirred for one hour, allowed to warm to room temperature and then stirred overnight. The reaction was then acidified with 5% hydrochloric acid (125 mL) to a pH of 2.8. The aqueous layer was extracted with 100 mL of ether twice and with 100 mL of ethyl acetate once. The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The crude material was dissolved in 100 mL of hot methanol and then refrigerated overnight. The crystals formed were filtered and dried under vacuum to afford 25.8 g of the desired 4-methyl-5-phenyl-2,4-pentadienoic acid. 1H NMR (acetone-d6, 300 MHz), δ(ppm) 7.53 (d, 1H), 7.43 (m, 4H), 7.37 (dd, 1H), 6.97 (broad s, 1H), 6.02 (d, 1H), 2.07 (s, 3H).
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