Epalrestat is a new remedy for diabetes sympatomaology. It can relieve diabetic retinopathy, dibetic motor never conduction inhabition. We synthesized it by rhodanine-3-actic acid and α-methyl- cinnamaldehyde. We researched Epalrestat's configurations and its preserved cinditions with HPLC, X-ray diffraction and high resolving NMR. We discovered, in Epalrestat's four stereo configurations, that (Z, E) is the most stable one (96.5%). But it is easy to transfer to (Z, Z) configuration in the sun light. (Z, E) configuration still has 93.5% in the mixture in dark after one year.

Key words: ACETIC ACID P, PHOTOSENSITIZATION, X-RAY DIFFRACTION ANALYSIS, HIGH SPEED LIQUID CHROMATOGRAPHY, THIAZOLE P, ISOMERIZATION, CONDENSATION, DIABETES MELLITUS