... The 2,5-dihydroxypyrazines are a remarkably in- teresting class of compounds in pyrazine chemistry since the predominant tautomer, 5-hydroxy-2(1H)-pyrazinone, was found to undergo a Diels-Alder reaction with electron- deficient ... [I] Part 1 3 N. Sato, J. Heterocyclic Chem., 23 ...