Stable equivalent of the ɑ-formylmalonate, valuable synthetic building block, particularly in heterocyclic syntheses. Review: Adv. Het. Chem., 54, (1992). Can be converted to the unstable diethyl methylenemalonate by catalytic reduction and elimination of ethanol on distillation, see: Org. Synth. Coll., 4, 298 (1963). Has been used for the protection of the amino group of ɑ-amino acids, allowing clean esterification by O-alkylation. The protecting group can be removed using bromine in chloroform: Synthesis, 544 (1989). For N-protection of aminoglycosides prior to O-acetylation, see: J. Carbohydr. Chem., 14, 1133 (1995).