Chiral effects on the /sup 13/C resonances of. cap alpha. -tocopherol and related compounds. A novel illustration of Newman's rule of six
The 100-MHz /sup 13/C NMR spectrum of (2R,4'R,8'R)-..cap alpha..-tocopherol (natural vitamin E) has been completely assigned with the aid of a number of selectively deuteriated (2R,4'R,8'R)-..cap alpha..-tocopherols. The /sup 13/C NMR spectrum of (2RS,4'RS,8'RS)-..cap alpha..-tocopherol (all-racemic, synthetic vitamin E) has also been measured. Many of the individual carbons in this all-racemic mixture of eight ..cap alpha..-tocopherol stereoisomers give more than one resonance with eight of the carbons (2-CH/sub 3/, 2',3',4',4'-CH/sub 3/, 5', 8', and 9') giving the maximum number of four resonances from each of the four enantiomeric pairs; these resonances have also been assigned. The structurally related 5'-hydroxy-2-(4',8',12'-trimethyltridecyl)-2,4,6,7-tetramethyl-2,3,-dihydrobenzofuran (HTDBF) has been synthesized for the first time in the 2R,4'R,8'R and 2S,4'R,8'R configurations and their /sup 13/C resonances have been assigned. In its all-racemic form this compound also shows up to four resonances from a single carbon. Related observations have been made with phytol and isophytol. A careful examination of these chirally induced chemical shift differences for the individual carbon atoms, ..delta.., reveals a bond-alternation effect with maxima at a separation of one, three, and five bonds from the closest chiral center and with the maximum at a five-bond separation being greater than that at a three-bond separation. 32 references, 2 figures, 4 tables.
- Research Organization:
- National Research Council of Canada, Ottawa, Ontario
- OSTI ID:
- 6085243
- Journal Information:
- J. Org. Chem.; (United States), Journal Name: J. Org. Chem.; (United States) Vol. 54:3; ISSN JOCEA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
CARBON 13
CARBON ISOTOPES
DATA
ENANTIOMORPHS
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
INFORMATION
ISOTOPES
LIGHT NUCLEI
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEI
NUMERICAL DATA
SPECTRA
STABLE ISOTOPES
VITAMIN E
VITAMINS