The synthesis of several@-keto phosphonates has been effected by the reaction of the carbanion derived from dimethyl methanephosphonate with appropriately substituted carboxylic acid esters. The presence of nucleophilic substituents y to the ketone in P-keto phosphonates leads to undesired intramolecular reactions, which can be prevented by temporarily protecting the ketone as an ethylene ketal. The title compound was obtained ...