Pyrazine, methyl affinity

Pyrido[2,3- ]pyrazine and its 2-, 3-, or 6-methyl derivatives were reacted with ethyl bromopyruvate in dimethylform-amide (DMF) to give 5-ethoxalylmethylpyrido[2,3- ]pyrazinium bromides 16-19, indicating the preferential nucleo-philicity at N-5. This is in agreement with the theoretical values of proton affinities of the pyrido[2,3-/ ]pyrazine ring system <1991JGC675, 1994H(38)283>. 

Quinuclidinyl- (195) and 1-azanorbornylpyrazine derivatives <92JMC295> as well as a series of (l,2,5,6-tetrahydro-l-methyl-3-pyridyl)pyrazines (196) <92JMC40ll> have been found to have high affinity for central muscarinic receptors. Such muscarinic agonists may provide an appropriate therapy for alleviating the memory deficiency associated with Alzheimer s disease. 

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