Date of Award

1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

A phytochemical investigation of ten species of the genus Aster (Family Asteraceae, Tribe Astereae) was carried out. The study involved the following taxa from the southern region of the United States: A. adnatus, A. concolor, A. dumosus x lateriflorus (a hybrid), A. lateriflorus, A. patens, A. praealtus, A. spinosus, A. subulatus var. ligulatus and A. tenuifolius as well as A. umbellatus from Pennsylvania. The chemical analysis of A. praealtus provided umbelliferone and seven prenylated coumarins of which four were new natural products. A ten-carbon acetylenic compound was isolated from A. spinosus. (DELTA)('7)- Sterols were found in A. adnatus which is of significance because generally (DELTA)('5)-sterols are the major structural type within the Asteraceae. The other species of Aster lacked coumarins. The structures of the compounds were established by spectroscopic methods, which include MS, IR, UV, single crystal X-ray diffraction analysis and extensive use of ('1)H NMR and ('13)C NMR spectroscopy. Analysis of A. praealtus, A. lateriflorus and A. subulatus var. ligulatus for volatile constituents by GC-MS resulte in monoterpenes and sesquiterpenes. Gundlachia corymbosa, of the tribe Astereae from the Bahamas, resulted in the isolation of diterpenoids and methoxylated flavonoids, the structures of which were determined by spectral methods. Capillary gas-liquid chromatography (GLC) and mass spectral studies were performed on several common skeletal types of sesquiterpene lactones. Capillary GLC proved to be an effective method for the separation of sesquiterpene lactones. Chemical ionization spectrometry was found to be a useful method for the determination of molecular weight, than the commonly used derivatization method of functional groups. Chemical ionization studies using NH(,3) and ND(,3) as reagent gases provided reliable molecular weights and the number of exchangeable hydrogen. The use of methane as reagent gas gave molecular weights and fragmentation patterns useful for structural studies.

Pages

286

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