ABSTRACT
The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the (13)C satellite doublets Δν'. This difference, Δ(Δν)=Δν'-Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the (13)C and (2)H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.
ABSTRACT
Pseudolarolides K(1) and L(2), two novel triterpenedilactones, were isolated from the seeds of Pseudolarix kaempferi, and their structures characterized from spectral data.
Subject(s)
Lactones/chemistry , Plants, Medicinal/chemistry , Trees , Triterpenes/chemistry , Lactones/isolation & purification , Nuclear Magnetic Resonance, Biomolecular/methods , Seeds/chemistry , Spectrometry, Mass, Fast Atom Bombardment , Stereoisomerism , Triterpenes/isolation & purificationABSTRACT
Pseudolarolide J (1), a novel nortriterpene lactone, has been isolated from the seeds of Pseudolarix kaempferi and structurally characterized from spectral data and X-ray crstallographic analysis.
