Molecules possessing harmine moiety are reported to exhibit marked fungicidal and bactericidal activities. In this study, various quinozilinium tetrafluoroborate salts were synthesized using acylic and cyclic oxoketene dithioacetals followed by cycloaromatization from Harmine. All of these synthesized compounds were characterized by 1H NMR, 13C NMR, Mass and CHN analysis. This methodology would find wide usage in the preparation of indolo quinozilinium -based library of small molecules useful for medicinal chemistry and in drug discovery.

    Abstract 
    Graphic abstract
    1 Introduction
    2 Results and discussion
        2.1 10-Methoxy-12-methyl-4-(methylthio)-2-phenyl-12H-indolo[2,3-a]quinolizin-5-ium tetra fluoroborate (4a)
        2.2 10-Methoxy-2-(4-methoxyphenyl)-12-methyl-4-(methylthio)-12H-indolo[2,3-a]quinoli zin-5-ium tetrafluoroborate (4b)
        2.3 2-(4-Chlorophenyl)-10-methoxy-12-methyl-4-(methyllthio)-12H-indolo[2,3-a]quino lizin-5-ium tetrafluoroborate (4c)
        2.4 10-Methoxy-12-methyl-4-(methylthio)-2-(pyridin-4-yl)-12H-indolo[2, 3-a] quinolizin-5-ium tetrafluoroborate (4d)
        2.5 2-(Furan-2-yl)-10-methoxy-12-methyl-4-(methylthio)-12H-indolo[2, 3-a] quinolizin-5-ium fluoroborate (4e)
        2.6 10-Methoxy-2,12-dimethyl-4-(methylthio)-12H-indolo[2,3-a]quinolizin-5-iumtetra fluoroborate (4f)
        2.7 11-Methoxy-13-methyl-5-(methylthio)-1,2,3,4,13-pentahydrocyclohexa[g]indolo[2,3-a] quinolizin-6-ium tetrafluoroborate (4g)
        2.8 13-Methoxy-15-methyl-7-(methylthio)-5, 6, 15-trihydronaphtho [3, 4-g] indolo [2, 3-a] quinolizin-8-ium tetrafluoroborate (4h)
        2.9 13-Methoxy-15-methyl-7-(methylthio)-6,15-dihydroindolo[2,3-a]thiochromeno[3,4-g]quinolizin-8-ium tetrafluoroborate (4i)
        2.10 13-Methoxy-3, 15-dimethyl-7-(methylthio)-6, 15-dihydroindolo [2, 3-a] thiochromeno [3, 4-g] quinolizin-8-ium (4j)
        2.11 10-Methoxy-12-methyl-2-phenyl-12H-indolo[2, 3-a] quinolizin-5-ium tetrafluoroborate (4k)
        2.12 10-Methoxy-12-methyl-2-phenyl-4-(pyrrolidin-1-yl)-12H-indolo[2, 3-a] quinolizin-5-ium tetrafluoroborate (4l)
        2.13 10-Methoxy-2-(4-methoxyphenyl)-12-methyl-4-(pyrrolidin-1-yl)-12H-indolo[2,3-a] quinolizin-5-ium tetrafluoroborate (4m)
        2.14 10-Methoxy-2,12-dimethyl-4-(pyrrolidin-1-yl)-12H-indolo[2,3-a]quinolizin-5-ium tetra fluoroborate (4n)
        2.15 3-Aza-10-methoxy-12-methyl-4-(methylthio)-2-phenyl-12H-indolo[2,3-a]quinolizin-5-ium tetrafluoroborate (4o)
    3 Experimental procedure
        3.1 General methods
        3.2 Chemicals and solvents
        3.3 Procedure for the preparation of N-methyl harmine
        3.4 General procedure for the quinozilinium fluoroborate salts (4a–o)
    4 Conclusions
    Acknowledgements 
    References

• Sivanath Musunuri(Department of Chemistry, ANR College, Gudivada)
• Reddymasu Sreenivasulu(Department of Chemistry, University College of Engineering (Autonomous), Jawaharlal Nehru Technological University)
• Kit‑Kay Mak(Pharmaceutical Chemistry Department, School of Pharmacy, International Medical University)
• Mallikarjuna Rao Pichika(Pharmaceutical Chemistry Department, School of Pharmacy, International Medical University)
• Mandava Venkata Basaveswara Rao(Department of Chemistry, Krishna University)