The synthesis of a versatile series of highly functionalized pyrimidinones is described, some of which served to test the feasibility of an intramolecular Diels-Alder approach to tetrodotoxin while others have been shown subsequently to serve as dienophiles in an intermolecular approach to the toxin. The series of 6-(acetic acid)-substituted pyrimidinones 4-12 and 15-21 were prepared from pyrimidinone ester amine 3. The series of 6- ...