Application of dimedone enamines as dienophiles: stereoselective synthesis of amino enols of fused uracils containing a sugar moiety by hetero-Diels–Alder reactions of barbituric acid 5-ylidene alditols with dimedone enamines

摘要: Abstract Dimedone enamines were applied for the first time as new dienophiles in hetero-Diels–Alder reactions with inverse electron demand. Cycloadditions of barbituric acid 5-ylidene alditols dimedone performed dichloromethane at room temperature 3 days and fused uracils–chromeno[2,3-d]pyrimidine-2,4-diones obtained good 73–87% yields. Only one enantiomerically pure stereoisomer was each studied cycloaddition. Analysis 1H NMR 2D spectra allowed determination that cycloadducts exist solution mixture neutral form dipolar ion. The prepared uracils contain both amine enol functional groups, so share amphiprotic properties they are zwitterions solid state. class compounds–amino enols synthesized, which similarly to amino acids exists zwitterions. In groups sugar moieties close other cis configuration axial position. It also shown different alkenes can be used towards alditols, example, styrene or 1-amino-2-thiocarbamoyl-cyclopent-1-ene.