Studies on terpenoids from Saussurea lappa Clarke
| dc.contributor.author | Banks, Calvin Mitchell | |
| dc.contributor.supervisor | Jain, Tikam C. | |
| dc.date.accessioned | 2025-04-24T21:05:29Z | |
| dc.date.available | 2025-04-24T21:05:29Z | |
| dc.date.issued | 1970 | |
| dc.degree.department | Department of Chemistry | |
| dc.description.abstract | This dissertation consists of two parts, part one deals with the N-bromosuccinimide-induced carbocyclization of germacranolides and some interesting aspects of their chemistry. Part two is concerned with the structure elucidation of an erroneously reported diterpene alcohol which was identified as 22-dihydrostigmasterol. Treatment of costunolide l and dihydrocostunolide 2 with NBS in aqueous acetone at room temperature furnished bromolactones 3, 4 and 5 and 6, 7, and 8 respectively. Structural evidence for these bromolactones rests upon spectral data and chemical correlations with santanolide 'c' 9 and related lactones. Unlike previous brominative cyclization studies, our substrates gave a variety of products in quantitative yields. This was attributed to the conformational control the y-lactone ring exercises over the germacrane skeleton. Also demonstrated was the reversible nature of the thermally induced valence isomerization of amine adduct 10 to dehydrosaussurea lactone amine adduct 11. Mild base treatment of the methiodide salt of adduct 11 yielded dehydrosaussurea lactone 12 which was needed for further NBS cyclization studies. Guided by the TT-TT interactions (Amax 211.5 nm) of substrate 12 a carbocyclization was predicted. Treatment of dehydrosaussurea lactone 12 with NBS in aqueous acetone at room temperature afforded bicyclic lactones 3, 4 and 5 which provided the first example of cyclization of a lactone based on the elemane framework. Thus a new dimension is added to the biosynthetic hypothesis of bicyclic sesquiterpenes, namely the intermediacy of elemanoids besides germacranolides in the biogenetic pathway of bicyclic sesquiterpenes. During this study it was found that dimethylamine cleaves y-lactone rings fused to six-membered systems yielding amides, whereas this does not occur with ten-membered rings. Also examined was a comparison of the elimination procedures for the regeneration of heat sensitive a, B-unsaturated y-lactones from their parent amine adducts. It was established that the mild base treatment was superior to the Hofmann method. Finally, the structure of vachanic acid is described. | |
| dc.description.scholarlevel | Graduate | |
| dc.identifier.uri | https://hdl.handle.net/1828/22006 | |
| dc.language.iso | en | |
| dc.rights | Available to the World Wide Web | |
| dc.title | Studies on terpenoids from Saussurea lappa Clarke | |
| dc.type | Thesis |