In Scheme I, step b, the alcohol (3) is oxidized to the ketone described by structure (5). For example, an equivalent of trifluoroacetic acid anhydride is added dropwise to 2 equivalents of dimethylsulfoxide in a suitable organic solvent, such as dichloromethane at approximately -60° C. After addition is complete, the reaction is stirred for approximately 2 minutes. An equivalent of an appropriately substituted alcohol (3), such as dimethyl 1,1-difluoro-2-hydroxy-4,8,12-trimethyl-3,7,11-tridecatrienylphosphonate dissolved in a suitable organic solvent, such as dichloromethane, is added to the reaction dropwise. After addition is complete, the reaction is stirred for approximately 45 minutes. The reaction is then cooled to -78° C. and an excess of triethylamine is added dropwise. The reaction is then allowed to warm to ambient temperature and stirred for approximately 45 minutes. The reaction mixture is then poured into water and extracted with a suitable organic solvent, such as diethyl ether. The organic phase is dried over a suitable drying agent, such as anhydrous magnesium sulfate, filtered and concentrated under vacuum. The residue is then purified by techniques well known in the art. For example, the residue can be purified by flash chromatography using a suitable organic eluent, such as 20% ethyl acetate/hexane, to provide dimethyl 1,1-difluoro-2-oxo-4,8,12-trimethyl-3,7,11-tridecatrienylphosphonate.
