A method is described for the synthesis of four geometric isomers of vitamin A, i.e., all-trans, neo, 6-cis and 2, 6-di-cis from cis- and trans-β-ionylideneacetaldehydes and senecioate (β, β-dimethylacrylate) via intermediate vitamin A acids. The condensation of β-ionylideneacetaldehydes and senecioates was effected by means of alkali amide.