An expeditious synthesis of β-pyrimidyl-α,β-didehydro-α-amino acid derivatives and pyrano[2,3-d]pyrimidines using microwave-assisted conditions

An expeditious transformation of 5-acyl-2H-pyran-2-ones with various amidines as 1,3-binucleophiles into isomerically pure (E)-α,β-didehydro-α-amino acid derivatives (DDAAD) containing the 5-pyrimidyl moiety at the β-position is described. The method was performed in ethanolic (or ethanol/water) solutions in the presence of Na2CO3 as a nontoxic base and under microwave-assisted conditions. When starting from the 5-ethoxycarbonyl-2H-pyran-2-one derivative and in the presence of DBU as a base the corresponding pyrano[2,3-d]pyrimidines were prepared.