[Transformation of betulin diacetate by the Prins reaction].

The interaction of betulin diacetate with formaldehyde by the Prins reaction in various media was studied. As a result, 3beta,28-di-O-acetyl-30-hydroxymethyl-(20)29-lupene, 3beta-acetyl-28-hydroxy-(20)29-lupene, and 3beta,28-di-O-acetoxy-19-(5',6'-dihydro-2'H-pyran-4'-yl)-20,29,30-trinorlupane were obtained.