Theoretical and UV spectral study of isomeric 1-(quinolinyl)-beta-carbolines conformations.
On the basis of beta-carboline (1) and 1-(quinolin-2'-yl)-beta-carboline (3) alpha- and t-band energies differences (Delta(alpha,t)) a equilibrium conformations of 1-(quinolin-4'(5'-8')-yl)-beta-carbolines (4-8) in solution have been estimated. Furthermore, as an example of model compounds 1-(alpha'-naphtyl)-beta-carboline (MC1) and 1-(beta'-naphtyl)-beta-carboline (MC2) and also 5 and 6 by molecular mechanics (mm+), semi-empirical (AM1) and none empirical (RHF/6-31G(d)) methods a computations of internal rotation of quinoline fragment around single bond have been performed. It was found that the greater bathochromic shift of the long-wavelength band maxima of 1, in the case of 3 (Deltalambda(max)=39 nm) relatively to 6, 7 (Deltalambda(max)=17+/-2 nm) and 4, 5, 8 (Deltalambda(max)=9+/-1 nm) caused by coplanarity of the molecule 3. Also, from experimental and theoretical investigations a less dihedral angle between beta-carboline and quinoline nucleous for 6, and 7 than 4, 5 and 8 owing to steric and electronic interactions have been found.
Eshimbetov
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S.Yu. Yunusov Institute of Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent 700170, Uzbekistan. ealisherg@yahoo.com
Tulyaganov
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D002243:Carbolines / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification; D007536:Isomerism; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D011804:Quinolines / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification; D012996:Solutions / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D028461:Zygophyllaceae / Q000737:chemistry
D002243:Carbolines; D011804:Quinolines; D012996:Solutions; C037219:quinoline