This account provides a short overview of the synthetically important class of formyl anions and the less studied formyl dianion equivalents. A brief literature survey, which particularly focusses on asymmetric homologation strategies, is complemented by a detailed description of lithiated (dimethoxymethyl)diphenylphosphane oxide, which is an ideal formyl anion equivalent in reactions with aldehydes. Under acidic conditions the intermediate ketene O,O-acetals afford homologated carboxylic esters whereas asymmetric dihydroxylation of ketene acetals leads to collapse of the intermediate diols furnishing the corresponding α-hydroxy carboxylic esters with high stereocontrol. Additionally, it is demonstrated that the silyl-substituted carbanion may be looked