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Keywords: 2-aminopyrimidine, 1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamides, bromination, antitubercular activity, X-ray structural analysis.Pyrimidine bases occur in a number of the most widespread heterocyclic systems in nature. Occurring in nucleic acids and coenzymes these compounds play a direct role in encoding and transmitting hereditary information, in the metabolism of carbohydrates and lecithin, and also in many biochemical processes important for animals and plants [2]. As a result, natural pyrimidines have an extremely broad spectrum of biological activities: from vitamins and regulators of biosynthesis amongst specific living organism proteins to antibiotics and alkaloids and to tetrodotoxin [3] which is one of the most powerful non-protein neurotoxins. Of course, pharmaceutical chemistry has not stood aside from the facts listed. As a result, to this day around 100 synthetic preparations [4] based on pyrimidine have been created and indeed used in medicinal practice. The majority of them fit into four broad categories of well known substances: barbiturates, sulfanilamides, antimicrobial pyrimidine-2,4-diamines, and antitumor agents [3]. Less impressive but none the less valuable for public health are such pharmacological groups as diuretics, antihypertensive and antihistamine agents, anticonvulsants, vitamins etc. [3,4].

Keywords: 2-aminopyrazine, 1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamides, bromination, antitubercular activity, X-ray structural analysis.In searching for novel chemotherapeutic agents suitable for treatment of many human infectious illnesses special interest has been paid to pyrazine derivatives. Based on this heterocycle efficient preparations have been created relating to different types of both aerobic and anaerobic bacteria [2-4] and to viruses (influenza [5], yellow fever [6], arenoviruses [7], HIV [8] etc). The reported high antitubercular activity of the unsubstituted amide and the 4-morpholylmethylamide of pyrazine-2-carboxylic acids (known under the names pyrazinamide and morinamide respectively [9]) has strongly stimulated a generally successful search for novel antimycobacterial medicinal agents amongst their structural analogs [10][11][12][13][14][15]. It is also interesting that many preparations containing a pyrazine ring have long been used medicinally for totally different indications, e.g. the diuretic amiloride and the antihypertensive benzamil where testing also showed them to be very good antitubercular agents [16].Based on this, it was totally logical and seemed promising also to involve 1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid pyrazin-2-ylamides 1a-m within the scope of studies of potential antitubercular agents which we carried out several years ago, in particular because high activity had already been repeatedly confirmed before in closely structurally related compounds.

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