Circular dichroism of tocopherols versus tocotrienols.
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 delta-tocopherol and its unsaturated analog delta-tocotrienol. TDDFT calculations demonstrate that the weak CD of delta-tocopherol is determined by the helicity of dihydropyrane ring. In addition, the moderate CD of delta-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.
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, 56126 Pisa, Italy.
Francesco
F
Mazzini
Gennaro
G
Pescitelli
Lorenzo
L
Di Bari
Thomas
T
Netscher
Piero
P
Salvadori
D002942:Circular Dichroism; D008958:Models, Molecular; D008968:Molecular Conformation; D009930:Organic Chemicals / Q000737:chemistry; D024505:Tocopherols / Q000737:chemistry*; D024508:Tocotrienols / Q000737:chemistry*
D009930:Organic Chemicals; D024508:Tocotrienols; C057718:6-(Dimethylamino)-2-((1E,3E)-4-(4-(dimethylamino)phenyl)-1,3-butadien-1-yl)-1-ethylquinolinium perchlorate; D024505:Tocopherols