The structure-activity relationships of two series of novel retinoids (2- pyrazinylcarboxamidobenzoates and β-ionylideneacetamidobenzoates) have been investigated by evaluating their ability to induce differentiation in both human promyelocytic leukemia (HL60) cells and mouse embryonal carcinoma (P19) cells. The most active compound (ED50= 8.3× 10-9 M) of the 2-pyrazinylcarboxamidobenzoates is 4-[2-(5, 6, 7, ...