302
J. C. Pardo-Novoa and C. M. Cerda-García-Rojas
OAng
O
283
OAng
282
OAng
O
281
OAng
OAng
O
OAng
280
OH
OAng
O
OAng
OAng
O
OAng
278
279
OAng
HO
277 (rasteviol)
OH
OAng
OH
O
287
OTs
O
OH
284
OH
OH
OH
285
286
OH
OH
O
Scheme 1 Transformation of rasteviol (277) into novel sesquiterpenoid structures by Wagner–
Meerwein molecular rearrangements
[119]. All structures were determined by NMR spectroscopy and mass spectrometry
in combination with single-crystal X-ray diffraction analyses of 284–287, which
supported the structural assignments and confirmed their absolute configurations by
calculation of Flack and Hooft parameters. The reaction mechanisms involved in the
molecular rearrangements were studied by deuterium-labeling experiments [119].
The bicyclic sesquiterpenoid parvifoline (288) was isolated in good yield from the
roots of Acourtia humboldtii, collected near Morelia, Mexico. This benzocyclooctene
was modified chemically to generate derivatives 289–299, which were studied as
tubulin polymerization inhibitors [120]. The structural analysis and characterization
of the new compounds 292–294 and 296–299 were achieved by NMR spectroscopy,