Synthesis And Bacteriostatic Activity Of New-type Chiral Pyrazine From β-pinene

β-pinene is natural chiral material and intermediate which is abundant in source. It hasspecific molecular space structure including two chiral carbon atoms and two prochiral cabonatoms. We studied on synthesis of new type pyrazine compounds from β-pinene and thebiological activity of these new compounds. It can be summarized as follows:3-methylenenopinone was synthesized by aldol condensation of nopinone andformaldehyde catalyzed with potassium hydroxide, and influences of the molar ratio ofnopinone to formaldehyde, types and dosages of catalysts, solvents, reaction temperature andreaction time on the aldol condensation were examined in detail. The optimum reactionconditions were determined according to the results of orthogonal experiments as follows:formaldehyde/nopinone molar ratio21:1; potassium hydroxide was used as the catalyst foraldol condensation, and KOH/nopinone molar ratio1.5:1; the reaction was conducted at65Cfor2h without solvent. The yield, purity and specific rotation of （+）-3-methylenenopinone was92.81%,98.4%and [α]_D²⁵+24.8（c0.5, CHCl₃） under the aforesaid conditions.（+）-2,3-Pindione was prepared by oxidation of （+）-3-methylene nopinone using potassiumpermanganate as the oxidant in acetone-H2O mixed solvent. In the oxidation process of（+）-3-methylenenopinone, influence of acetone/H2O ratio, dosages of KMnO₄, reactiontemperature and reaction time on the oxidation were investigated in detail, and the optimumoxidation conditions were determined according to the results of orthogonal experiments asfollows: acetone/H2O ratio10:1（v/v）; potassium permanganate was used as the oxidant, andn（KMnO₄）:n（3-Methylenenopinone） molar ratio3:1; the reaction temperature5C; reactiontime6h. The yield, purity and specific rotation of （+）-2,3-pindione was75.13%,98.88%and[α]_D¹⁶+255.4（c0.5, CHCl₃） under the aforesaid conditions.A series of bisimines were prepared by reaction of2,3-pindione and diamines includingethylenediamine, o-phenylenediamine,1,2-propylene diamine, cyclohexanediamine protectedwith nitrogen using cyclohexane or toluene as the solvent, and Amberlyst15as the catalyst. Thereaction selectivitirs were in the range of91%¹00%and all of them had optical activities.Pyrazines were prepared by dehydrogenation of bisimmine using alumina or zinc oxide as thedehydrogenating agent in ethanol. The reaction selectivitirs were in the range of95%¹00%,and all of them had optical activities. The structures of3-methylene-nopinone,2,3-pinanedione,imines Schiff and pyrazine were determined by IR,¹HNMR,¹³CNMR, and MS spectra.Antifungal and bacteriostatic biological activities about all synthesized compounds were tested.The results indicated that the bacteriostatic biological activities of intermediate, imines Schiffand pyrazines were significantly greater than antifungal biological activities of thesecompounds. Among them,3-methylenenopinone （2-a）, heterocyclic triketone（3-b） had stronginhibition to E.coli, S.aureus and B.subtilis. Inhibitory effect on E.coli and S.aureus of imines Schiff（4-a） and pyrazines（4-b,5-c） is stronger than others. Pyrazines（4-b） had the strongestinhibition on B.subtilis.