A preparatively convenient and efficient method is proposed for the synthesis of novel 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-8-carboxylic acids, based on the reaction of (3-oxopiperazine-2-ylidene)ethanoates with 2-bromo-1,1-diethoxyethane and accomplished through the stage of intermediate methyl 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-8-carboxylates, which were also isolated as individual compounds. A method of directly transforming 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-8-carboxylic acids into 1-oxo-N-(alkyl)aryl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-8-carboxamides via the former’s interaction with aliphatic and aromatic amines in the presence of DIPEA and HATU was developed, with yields of 31–78%. A reliable structural determination of all the synthesized compounds has been performed by elemental analysis and a number of spectroscopic methods (¹H and ¹³C NMR, HPLC/MS) as well as by X-ray diffraction analysis. Biological screening of all types of synthesized compounds revealed their moderate antibacterial and antifungal activity. The antioxidant effect level of the most active carboxamides was in the range of 59.3–74.5%, as compared to ascorbic acid (97.3%).

Graphical abstract

中文翻译：

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新型1-氧代-1,2,3,4-四氢吡咯并[1,2-a]吡嗪-8-羧酸及其酯和酰胺的合成、抗菌和抗氧化活性

基于(3-氧代哌嗪- 2-亚基)乙酸酯与2-溴-1,1-二乙氧基乙烷通过中间体1-氧代-1,2,3,4-四氢吡咯并[1,2- a ]吡嗪-8-甲酸甲酯阶段完成，也作为单独的化合物被分离出来。一种将1-氧代-1,2,3,4-四氢吡咯并[1,2- a ]吡嗪-8-羧酸直接转化为1-氧代-N- (烷基)芳基-1,2,3,4的方法-四氢吡咯并[1,2- a]吡嗪-8-甲酰胺通过前者在 DIPEA 和 HATU 存在下与脂肪族和芳香族胺相互作用而开发出来，产率为 31-78%。通过元素分析和多种光谱方法（¹ H 和¹³ C NMR、HPLC/MS）以及 X 射线衍射分析，对所有合成的化合物进行了可靠的结构测定。对所有类型的合成化合物的生物学筛选表明它们具有中等的抗菌和抗真菌活性。与抗坏血酸 (97.3%) 相比，最活跃的羧酰胺的抗氧化效果水平在 59.3-74.5% 范围内。

图形概要