4-[3-(3-vinyl-1-acetyl-4-piperidyl)-1-propenyl]-6-methoxyquinoline, the corresponding epoxide and related compounds, useful in the synthesis of Cinchona alkaloids, are prepared by introducing an ylid group in the 4-position of a suitably substituted quinoline and reacting this ylid with an N-acetyl-4-piperidineacetaldehyde.