THE REACTION OF 2-AMINO-2-DEOXYHEXOPYRANOSES WITH ISOCYANATES, SYNTHESIS OF UREAS AND THEIR TRANSFORMATION INTO HETEROCYCLIC-DERIVATIVES

The reactions of 2-amino-2-deoxyglycopyranoses with aryl isocyanates have been investigated in detail and ureas and heterocyclic derivatives are obtained. The mechanism of formation of glycofurano[2,1-d]imidazolidin-2-ones 62 has now become visible, while previous reports and the classical literature dealing with the subject in question proposed alternative structures for the reaction products. The reactions are pH-dependent and only furanoid bicycles are smoothly obtained at acidic pH values, whereas in neutral or basic media 5-hydroxyimidazolidin-2-one derivatives 66 can be isolated. These monocyclic structures appear to be the true intermediates of the reaction and, under appropriate conditions, can be converted exclusively into the corresponding cis-fused five-membered ring systems. Likewise, the first cis-fused glycopyrano[2,1-d]imidazolidin-2-ones 75 have been also prepared.