17,20beta,21-Trihydroxypregn-4-ene-3,11-dione 20-Dihydrocortisone 3615-87-0 4-Pregnene-17alpha,20beta,21-triol-3,11-dione Pregn-4-ene-3,11-dione, 17,20,21-trihydroxy- Reichstein's substance U