[PH:1](=[O:4])([O-])[O-].[C:5]([OH:12])(=O)[CH2:6][CH2:7][CH2:8][CH:9]=[CH2:10].S(=O)(=O)(O)O.[CH2:18]([Li])CCC.[C:23]([O:30][CH3:31])(=[O:29])[CH2:24][CH2:25][CH2:26][CH:27]=[CH2:28].[C:32]([OH:35])(=O)C>O1CCCC1.C(Cl)CCl.CO>[C:23]([O:30][CH3:31])(=[O:29])[CH2:24][CH2:25][CH2:26][CH:27]=[CH2:28].[O:12]=[C:5]([CH2:6][CH2:7][CH2:8][CH:9]=[CH2:10])[CH2:18][P:1](=[O:4])([O:30][CH3:31])[O:35][CH3:32]Via Lactone XXXVII. Refer to Chart 3. A phosphonate reagent is first prepared. Methyl 5-hexenoate is prepared from 5-hexenoic acid by reaction with methanol and concentrated sulfuric acid in refluxing ethylene dichloride, thereafter washing and distilling the product. The anion of dimethyl methylphosphonate, prepared from dimethyl methylphosphonate (82 g.) and 400 ml. of 1.6 M butyllithium in 800 ml. of tetrahydrofuran at -55° to -60° C. is treated with methyl 5-hexenoate (41 g.) added in 65 ml. of tetrahydrofuran over about 10 min. The mixture is stirred at -75° C. for 2 hr. and then at about 25° C. for 18 hr. Acetic acid (26 ml.) is added and the solvent removed under reduced pressure. The residue is taken up in water and ether-methylene chloride (3:1). The organic phase, combined with extractions of the aqueous phase, is washed with cold aqueous sodium bicarbonate and brine, dried, and concentrated. There is obtained, on distillation, dimethyl 2-oxo-6-heptenylphosphonate.
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