ChemInform Abstract: LANTHANIDE SHIFT REAGENTS IN (13)C NUCLEAR MAGNETIC RESONANCE, QUANTITATIVE DETERMINATION OF PSEUDOCONTACT SHIFTS AND ASSIGNMENT OF (13)C CHEMICAL SHIFTS OF STEROIDS

1974 ◽  
Vol 5 (11) ◽  
Author(s):  
JOHN W. APSIMON ◽  
HELMUT BEIERBECK ◽  
JOHN K. SAUNDERS
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Quantitative Determination ◽  
Chemical Shifts ◽  
Pseudocontact Shifts ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents ◽  
Nuclear Magnetic

Lanthanide Shift Reagents in 13C Nuclear Magnetic Resonance: Quantitative Determination of Pseudocontact Shifts and Assignment of 13C Chemical Shifts of Steroids

1973 ◽  
Vol 51 (23) ◽  
pp. 3874-3881 ◽  
Author(s):  
John W. ApSimon ◽  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Shift Reagent ◽  
Pseudocontact Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Lanthanide Shift Reagents ◽  
Shift Reagents ◽  
The One

The l3C n.m.r. chemical shifts of some monofunctional keto- and hydroxy-steroids were monitored as a function of the concentration of added shift reagent, Pr(fod)3 or Eu(fod)3, and the observed induced shifts were fitted to the geometric quantities in the one-term pseudocontact shielding equation. The correlation between experimental and calculated shifts was quantitative for all carbons except those closest to the complexing site, where contact interactions are most noticeable. With Pr(fod)3 the carbonyl and hydroxyl carbons and the alpha carbons usually had to be excluded from the calculations in order to optimize the correlation between predicted and observed induced shifts for the remaining nuclei and to derive reasonable adduct geometries. With Eu(fod)3, contact shifts were also noticeable at the beta carbons and the europium shift reagents are therefore less useful in 13C n.m.r. spectroscopy. It is shown that the application of shift reagents, in conjunction with off-resonance decoupling, permits the assignment of practically all carbon chemical shifts of the steroids studied.

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