Date of Award

1988

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Nikolaus H. Fischer

Abstract

Chemical analysis of root cultures of Tagetes patula (Asteraceae) provided the knowns 5-acetyl-4-hydroxy-2-isopropenyl-benzofuran, 5-(but-3-en-1-ynyl)-2,2$\sp\prime$-bithiophene and 5-(4-acetoxy-1 butynyl)-2,2$\sp\prime$-bithiophene. Their structures were elucidated by spectroscopic methods. Chemical analysis by capillary gas-liquid chromatography-mass spectrocscopy (GC/MS) of Parthenium argentatum (Guayule) provided the known sesquiterpene hydrocarbons 9,10-dihydroguajene, $\alpha$-copaene, alloaromandrene, isolongifolene, germacrene A or $\beta$-elemene and $\alpha$-humulene. The known sesquiterpene esters guayulin A and B and the triterpenes argentatin A and B as well as two new cycloartenol-type triterpenes, 3$\alpha$- and 3$\beta$-hydroargentatin B, were also isolated. The relative configuration, the conformation as well as the $\sp1$H and $\sp{13}$C NMR resonance assignments of the two new triterpenes were established by 2D and multipulse NMR techniques. Hydrolysis of guayulin A yielded desacylguayulin A, a stereochemical study of which was performed using modern NMR techniques. Chemical analysis of Baccharis salicina (Asteraceae) yielded the known antitumor flavone centaureidin and two new guaianolides, bacchariolides A and B. Their structures were elucidated by spectroscopic methods. Biomimetic-type reactions of the sesquiterpene lactone 11,13-dihydroparthenolide involved the following transformations: (1) BF$\sb3$-mediated rearrangement of the germacrolide 4(5)-epoxide to produce a xanthanolide and three cis-guaianolides. (2) m-Chloroperoxybenzoic acid mediated oxidation-rearrangements of a guaianolide 1(10)-ene to produce a xanthanolide, a trans-epoxy-guaianolide, two cis-epoxy-guaianolides and a cyclobutane-type sesquiterpene lactone. (3) BF$\sb3$-catalyzed rearrangement of a guaianolide 1(10)-$\beta$-epoxide to give a cis-eudesmanolide, a trans-guaianolide, and two cis-guaianolides. The results and proposed mechanisms of these reaction sequences as well as the detailed structure elucidation of the transformation products are described.

Pages

117

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