Synthesis and investigation of antimicrobial activity of 8-hydroxyquinoline glucosaminides

NMR study of O and N, O‐substituted 8‐quinolinol derivatives

“…An aqueous solution of 8‐quinolinol helps in quick germination of Eriobotrya japonica ( loquat ) . Recently, antimicrobial activity of oxine glucosaminides and anti‐inflammatory activity of 8‐quinolinol Mannich bases have been reported. Current work involves the NMR spectral study of various 8‐quinolinol derivatives ( 2–21 ) possessing antimicrobial and antiplatelet aggregating activities .…”

“…[6] Recently, antimicrobial activity of oxine glucosaminides [7] and anti-inflammatory activity of 8-quinolinol Mannich bases [8] have been reported. Current work involves the NMR spectral study of various 8-quinolinol derivatives (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) possessing antimicrobial [9] and antiplatelet aggregating activities. [10] This is the first report of NMR data for compounds 6, 17-21 according to the Science Finder research engine ( Fig.…”

“…Preparation of benzyloxy (7) and N, O-dibenzyl (21) derivatives Sodium hydroxide (1.0 g) and benzyl chloride (3 ml) were added to a solution of 8-quinolinol (1, 2.0 g) in dimethyl sulfoxide (4.0 ml) and kept under normal conditions of temperature and pressure for 2 days. On usual workup of reaction mixture (as mentioned for 2-6 and 16-21), the ethyl acetate phase yielded 8-benzyloxy quinoline (7, 1.0 g).…”

“…These assignments were transferred to C-2 to C-7 through HeteroCOSY, whereas that for quaternary carbons was made through 13 C NMR and literature. [14] Nucleophilic substitution reaction of 8-quinolinol with different reagents produced several 8-O-substituted derivatives (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and N-alkyl, 8-alkoxy quinolinium halides (16-21). It is worth mentioning that multiplicities in 8-benzyloxy quinoline (7), 8-cinnamoyloxy (12), and 8-crotonyloxy (13) were better resolved in DMSO-d 6 (Tables 1-4).…”

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The 1 H and 13 C NMR spectral study of several biologically active derivatives of 8-quinolinol have been made through extensive NMR studies including homodecoupling and 2D-NMR experiments such as COSY-45°, NOESY, and HeteroCOSY. Electron donating resonance and electron withdrawing inductive effect of several groups showed marked changes in chemical shifts of nuclei at the seventh positions of O-substituted quinolinols (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Although in N-alkyl, 8-alkoxyquinolinium halides (16-21), ring A rightly showed low frequency chemical shift values.

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