1. Substituted Ureas. Methods of Synthesis and Applications
2. Antiviral and pharmacokinetic properties of C2 symmetric inhibitors of the human immunodeficiency virus type 1 protease
3. Discovery of a novel class of potent HIV-1 protease inhibitors containing the (R)-(hydroxyethyl)urea isostere
4. The most important of the wide variety of methods to prepare mono- di- and trisubstituted ureas1,5mostly fall into three main groups. In the first place, primary amines are reacted with carbonyl insertion compounds such as phosgene,5trisphosgene,6various carbonates,7-9S,S-dimethyl thiocarbonate,10andN,N‘-carbonyldiimidazole.11The second class comprises the reactions of primary amines with NCO equivalent compounds like carbamates,12-14formamides (in the presence of a ruthenium catalyst),15and most importantly isocyanates.5,16Thirdly, ureas have been prepared by the catalyzed carbonylation of amines using carbon monoxide17-20or carbon dioxide21,22in the presence of metal complexes, selenium,17phosphorus compounds,23,24andN,N‘-dicyclohexylcarbodiimide.25