Flavors pyrimidines

The diazines pyridazine, pyrimidine, pyrazine, and their benzo derivatives cinnoline, phthalazine, quinazoline, quinoxaline, and phenazine once again played a central role in many investigations. Progress was made on the syntheses and reactions of these heterocycles, and their use as intermediates toward broader goals. Some studies relied on solid-phase, microwave irradiation, or metal-assisted synthetic approaches, while others focused attention more on the X-ray, computational, spectroscopic, and natural product and other biological aspects of these heterocycles. Reports with a common flavor have been grouped together whenever possible. 

Pyrimidine derivatives do not generally have positive flavor notes and are considered neutral to poor. Some pyrimidine-derived flavors (although not found in tobacco or tobacco smoke) have meaty notes. There are also some pyrimidine flavorants that do possess good flavor potential for tobacco products, for example, 2-methyl-5,7-dihydrothieno[3,4- (]pyrimidine. This compound contains a bicyclic ring structure and has been identified in tobacco. 2-Methyl-5,7-dihydrothieno[3,4- (]pyrimidine is said to have a fresh roasted, sweet nut flavor with a popcorn character (17B22). It is a compound listed by Doull et al. as an ingredient in flavor formulations used by one or more members of the U.S. tobacco industry (1053). 

Properties Colorless liq., brandy-like odor, sweet si. fruity flavor sol. in alcohol insol. in water m.w. 158.20 dens. 0.9697 b.p. 84.5 C (11 mm) flash pt. 173 F ref. index 1.4219 Uses Synthesis of heterocyclics (furanes, pyrazolones, isoxazoles, pyrimidines), drugs synthetic flavoring agent in foods and pharmaceuticals Features Fruity flavor... 

The thermal generation of flavor is a very essential process for the "taste" of many different foodstuffs, e.g. cocoa, coffee, bread, meat. The resulting aromas are formed through non-enzymatic reactions mainly with carbohydrates, lipids, amino acids (proteins), and vitamins under the influence of heat. Thiamin (vitamin B ) and the amino acids, cysteine and methionine, belong to those food constituents which act as flavor precursors in thermal reactions. The role of thiamin as a potent flavor precursor is related to its chemical structure which consists of a thiazole as well as a pyrimidine moiety. The thermal degradation of this heterocyclic constituent leads to very reactive intermediates which are able to react directly to highly odoriferous flavor compounds or with degradation products of amino acids or carbohydrates. 

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