Studies on Ethylenic Compounds. III. Hydrazone-type Derivatives of Vitamin A Aldehyde

It was found that the crystalline derivatives were readily obtainable when various hydrazine compounds were reacted with retinal. Many hydrazone-type derivatives of retinal were prepared and their physical properties, stability, toxicity and biopotency were examined. All such derivatives are more stable than vitamin A palmitate, their toxicity being low, and some of them showed considerably higher vitamin A activity. Retinal azine is obtained as crystals of m. p.189° in a good yield when retinal is reacted with hydrazine-hydrate in the presence of an organic acid as a promotor. This compound is expected to have higher biological activity. p-Aminobenzoylhydrazone of retinal showed the biopotency equivalent to that of vitamin A.