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Deshielded nucleus

The NMR signal of a shielded nucleus appears more upheld than the signal for a deshielded nucleus. (11.7)... [Pg.400]

Deshielding (Section 13.2) An effect observed in NMR that causes a nucleus to absorb downfield (to the left) of tetramethylsilane (TMS) standard. Deshielding is caused by a withdrawal of electron density from the nucleus. [Pg.1239]

Examination of the C-NMR spectra of roseadine (23) (Table XI) through comparison with vindoline (3) and leurosine (11) permitted the assignment of all carbons of the dihydroindole unit. The carbons of the indole nucleus were assigned by comparison with vinblastine (1), and the presence of three deshielded carbons, a methine carbon at 8 142.9 and two quaternary carbons at 8 133.2 and 169.2, were observed. The latter was assigned to the methoxycarbonyl carbon, which is shielded somewhat from its characteristic chemical shift of 8 174 1 ppm in the vinblastine series by attachment of an olefinic unit. The other two deshielded carbons at 8 133.2 and 142.9 could be assigned as C-18 and C-17, respec-... [Pg.27]

See other pages where Deshielded nucleus is mentioned: [Pg.75]    [Pg.58]    [Pg.500]    [Pg.501]    [Pg.158]    [Pg.503]    [Pg.57]    [Pg.1709]    [Pg.75]    [Pg.58]    [Pg.500]    [Pg.501]    [Pg.158]    [Pg.503]    [Pg.57]    [Pg.1709]    [Pg.1445]    [Pg.1]    [Pg.1040]    [Pg.250]    [Pg.68]    [Pg.205]    [Pg.24]    [Pg.59]    [Pg.61]    [Pg.93]    [Pg.87]    [Pg.8]    [Pg.530]    [Pg.370]    [Pg.100]    [Pg.454]    [Pg.298]    [Pg.104]    [Pg.170]    [Pg.242]    [Pg.245]    [Pg.216]    [Pg.215]    [Pg.17]    [Pg.21]    [Pg.22]    [Pg.22]    [Pg.30]    [Pg.35]    [Pg.41]    [Pg.65]    [Pg.66]    [Pg.67]    [Pg.68]    [Pg.82]    [Pg.90]    [Pg.90]    [Pg.96]    [Pg.100]   
See also in sourсe #XX -- [ Pg.566 ]



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Deshielded

Deshielding

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