274
J. C. Pardo-Novoa and C. M. Cerda-García-Rojas
by application of the modified Mosher’s methodology. It is interesting to note that
spirolingshuiolide (125) was classified as the first case of a sesquiterpene with a
rearranged drimane framework [54].
O
O
R
3
R
1
R
2
O
O
OH
O
O
O
O
O
O
O
O
121 R
1 = R
3 = OH, R
2 = H (lingshuiolide A)
122 R
1 = H, R
2 = R
3 = OH (lingshuiolide B)
123 (lingshuiperoxide)
124 (isodysetherin)
125 (spirolingshuiolide)
A chemical study on the gorgonian coral Menella woodin, collected from Vietnamese coastal areas, allowed two new sesquiterpene lactones of the guaiane-type
to be obtained. Their structures, represented by 126 and 127, were elucidated by
extensive spectroscopic analysis that included the comparison between experimental
and DFT-calculated NMR spectra. Their absolute configurations were determined
by comparison between experimental and calculated optical rotations and electronic circular dichroism spectra, using quantum-chemical methods with the timedependent DFT calculations at the B3LYP/6-311G(d,p) level of theory and using the
polarizable continuum model for solvation effects. The stereochemical information
was supplemented with application of the Mosher’s method on compound 126 that
provided results consistent with those obtained by the quantum calculations [55].
HO
O
O
O
HO
O
O
HO
O
7
2
1
6
2
1
2.5 Use of Cryoprobes for NMR Measurements
Microscale NMR techniques using cryoprobes have expanded the versatility of new
methods for structure elucidation of complex natural compounds that are present in
very small amounts in rare organisms. Microprobe NMR spectroscopy, microscale
degradation and synthesis, are synergistic tools for the discovery of bioactive natural
J. C. Pardo-Novoa and C. M. Cerda-García-Rojas
by application of the modified Mosher’s methodology. It is interesting to note that
spirolingshuiolide (125) was classified as the first case of a sesquiterpene with a
rearranged drimane framework [54].
O
O
R
3
R
1
R
2
O
O
OH
O
O
O
O
O
O
O
O
121 R
1 = R
3 = OH, R
2 = H (lingshuiolide A)
122 R
1 = H, R
2 = R
3 = OH (lingshuiolide B)
123 (lingshuiperoxide)
124 (isodysetherin)
125 (spirolingshuiolide)
A chemical study on the gorgonian coral Menella woodin, collected from Vietnamese coastal areas, allowed two new sesquiterpene lactones of the guaiane-type
to be obtained. Their structures, represented by 126 and 127, were elucidated by
extensive spectroscopic analysis that included the comparison between experimental
and DFT-calculated NMR spectra. Their absolute configurations were determined
by comparison between experimental and calculated optical rotations and electronic circular dichroism spectra, using quantum-chemical methods with the timedependent DFT calculations at the B3LYP/6-311G(d,p) level of theory and using the
polarizable continuum model for solvation effects. The stereochemical information
was supplemented with application of the Mosher’s method on compound 126 that
provided results consistent with those obtained by the quantum calculations [55].
HO
O
O
O
HO
O
O
HO
O
7
2
1
6
2
1
2.5 Use of Cryoprobes for NMR Measurements
Microscale NMR techniques using cryoprobes have expanded the versatility of new
methods for structure elucidation of complex natural compounds that are present in
very small amounts in rare organisms. Microprobe NMR spectroscopy, microscale
degradation and synthesis, are synergistic tools for the discovery of bioactive natural