SYNTHESIS OF 5-HYDROXYDIHYDROPYRIMIDINE DERIVATIVES AND THE INFLUENCE OF INTRAMOLECULAR HYDROGEN BONDING ON THEIR NMR PROPERTIES AND CONFORMATIONAL PREFERENCES OF THE HYDROXYL GROUP

A series of 2,2'-(5-hydroxydihydropyrimidine-1,3(2H, 4H)-diyl) bis-(methylene)-disubstitutedphenols was synthesized by using a Mannich-type reaction between 1,3-diaminopropan-2-ol, paraformaldehyde and substituted phenols. These previously unreported compounds were separated from the reaction mixture by column chromatography (CC) in highly pure form with a 29%-91% yield. The effect of intramolecular hydrogen bonding on the conformation of 5-hydroxyhexahydropyrimidines has been studied. Our results show that the presence of hydroxyl groups can strongly influence the stereoelectronic relationships in the six-membered heterocyclic ring.