Sur l'arôme de viande de boeuf grillée II. Dihydro‐6,7‐5H‐cyclopenta[b]pyrazines, identification et mode de formation

Identification of alkyl‐5H‐6,7‐dihydrococyclopenta[b]pyrazines in roasted meat flavor. Model reaction used as basis for natural product formation and new synthesis. Seven alkyl‐5H‐6,7‐dihydrocyclopenta[b]pyrazines have been identified in a roasted meat aroma obtained by thermolysis of the hydrosoluble flavor precursors of raw meat. Formation of these heterocyclics by condensation of hydroxycyclopentenones with aliphatic α‐dicarbonyl compounds in the presence of ammonia has been confirmed by a model reaction. Alkyl‐5H‐cyclopenta[b]pyrazines and dicyclopenta [b,e]pyrazines are also obtained from this reaction, but have not yet been identified in roasted flavors. Preparation of the intermediates of the model reaction enabled development of an economical synthesis of 2,3,5‐trimethyl‐5H‐6,7‐dihydrocyclopenta[b]pyrazine.