An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with ^(4)JC,H long-range correlation by prolonging the acquisition time at ^(2,3)JC,H values of 2.0 and 8...An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with ^(4)JC,H long-range correlation by prolonging the acquisition time at ^(2,3)JC,H values of 2.0 and 8.0Hz.Furthermore,the ^(1)H(proton)nuclear magnetic resonance(NMR)pattern of phenolic hydroxyl protons was developed as a“diagnosis signal”to ascertain the relative location of each side chain in DMSO-d_(6) at sample concentrations of 0.022-0.034 mol/L.The chemical shift differences of 0.6ppm between OH-5' and OH-1 and between OH-8'and OH-4 are assigned to Type A and Type B,respectively.All reported ambiguous structures were corrected by this pattern.Additionally,the steric structures of isolated compounds were elucidated by quantum chemical calculations of electronic circular dichroism(ECD)spectra.展开更多
基金funded by the CAMS Innovation Fund for Medical Sciences(CIFMS,No.2021-I2M-1-028).
文摘An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with ^(4)JC,H long-range correlation by prolonging the acquisition time at ^(2,3)JC,H values of 2.0 and 8.0Hz.Furthermore,the ^(1)H(proton)nuclear magnetic resonance(NMR)pattern of phenolic hydroxyl protons was developed as a“diagnosis signal”to ascertain the relative location of each side chain in DMSO-d_(6) at sample concentrations of 0.022-0.034 mol/L.The chemical shift differences of 0.6ppm between OH-5' and OH-1 and between OH-8'and OH-4 are assigned to Type A and Type B,respectively.All reported ambiguous structures were corrected by this pattern.Additionally,the steric structures of isolated compounds were elucidated by quantum chemical calculations of electronic circular dichroism(ECD)spectra.
