Vitamin E is an essential nutrient of still increasing economic importance. Vitamin E derivatives include many nonracemic chiral compounds whose chirooptical characterization is scarcely described in the literature. We report the CD spectra of d-tocopherol and its unsaturated analog d-tocotrienol. TDDFT calculations demonstrate that the weak CD of d-tocopherol is determined by the helicity of dihydropyrane ring. In addition, the moderate CD of d-tocotrienol is due to the exciton interaction between the aromatic ring and the closest alkene group. Direct exciton-coupled CD calculations on structures generated by two different conformational sampling approaches reveal that, although such exciton coupling is expected to be weak, it is sufficient to explain the spectral differences between tocopherol and tocotrienol.
Circular Dichroism of Tocopherols Versus Tocotrienols
PESCITELLI, GENNARO;DI BARI, LORENZO;SALVADORI, PIERO
2009-01-01
Abstract
Vitamin E is an essential nutrient of still increasing economic importance. Vitamin E derivatives include many nonracemic chiral compounds whose chirooptical characterization is scarcely described in the literature. We report the CD spectra of d-tocopherol and its unsaturated analog d-tocotrienol. TDDFT calculations demonstrate that the weak CD of d-tocopherol is determined by the helicity of dihydropyrane ring. In addition, the moderate CD of d-tocotrienol is due to the exciton interaction between the aromatic ring and the closest alkene group. Direct exciton-coupled CD calculations on structures generated by two different conformational sampling approaches reveal that, although such exciton coupling is expected to be weak, it is sufficient to explain the spectral differences between tocopherol and tocotrienol.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
