Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 6 of 6
Full-Text Articles in Entire DC Network
New Sesquiterpene Lactones From The Genera Calea And Berlandiera (Asteraceae) And The Fragmentation Reactions Of 1,3-Dihydroxyeudesmanolide Derivatives., Ihl Young Lee
LSU Historical Dissertations and Theses
Chemical analysis of Calea ternifolia var. calyculata (syn. Calea hypoleuka, Calea salmaefolia, and Calea albida) yielded the known sesquiterpene lactone calein A (21) and the atripliciolide derivatives, 11,13-dyhydro-11(alpha),13-epoxyatripliciolide-8(beta)-O-angelate (51), 11,13-dihydro-11(alpha),13-epoxyatripliciolide-8(beta)-O-methacrylate (52), and 9(alpha)-hydroxy-11,13-dihydro-11(alpha),13-epoxyatripliciolide-8(beta)-angelate (54). In addition, three new germacranolides, 8(beta)-angeloyloxy-9(alpha)-{2-methylbutanoyloxy} ternifolin (32), 8(beta)-angeloyloxy-9-acetoxyternifolin (33) and five furanoheliangolides, 9(alpha)-acetoxyzexbrevin (36), 9(alpha)-hydroxyzexbrevin (37), 8(beta)-angeloyloxy-9(alpha)-hydroxycalyculatolide (38), 9(alpha)-hydroxy-11,13-dihydro-11(alpha),13-epoxyatripliciolide 8(beta)-O-methacrylate (55) and 15-hydroxy-11,13-dihydro-11(alpha),13-epoxyatripliciolide (56) were isolated. The structures of the new compounds were elucidated by NMR and mass spectral methods. Single crystal X-ray diffraction of the lactones 36 and 55 established their molecular structure. Calea ternifolia var. ternifolia (syn. Calea liebmanii) provided the new sesquiterpene …
The Syntheses Of The Crown Ethers Possessing 2,6-Pyridino Moieties., Hyo Won Lee
The Syntheses Of The Crown Ethers Possessing 2,6-Pyridino Moieties., Hyo Won Lee
LSU Historical Dissertations and Theses
In an attempt to synthesize "Type 2" nicotinic acid crown ethers with a 3-carbinol appendage group, unexpected facile etherification was encountered during the cleavage of the tetrahydropyranyl (THP) group in acidic alcoholic media. The rationale for this reaction was provided by the examination of reactions with non-cyclic model compounds, and their THP derivatives in order to isolate any effects of the crown ether bridge. The 2,6-disubstituted dialkoxy groups were found to contribute to the stabilization of the carbonium ion derived from the protonation of the 3-pyridyl carbinols. Thus, nicotinic crown ether with a 3-carbinol group was prepared with the exclusion …
Synthesis And Characterization Of Novel Pyridine And Dipyridine Metallocyclic Palladium Complexes., Wallace Earl Puckett
Synthesis And Characterization Of Novel Pyridine And Dipyridine Metallocyclic Palladium Complexes., Wallace Earl Puckett
LSU Historical Dissertations and Theses
The synthesis of palladocycles containing trans and cis C-metal anionic sigma bonds has been accomplished. The trans ligands were prepared from 2,6-bis(chloromethyl)pyridine and alkyl malonates by a base catalyzed S(,N)2 reaction. This cis-ligands were formed by a similar reaction but using 6,6'-bis(chloromethyl)-2,2'-dipyridine as starting halide. The synthesis of the latter chloro compound is discussed in detail. The trans complexes were prepared by base mediated cyclometallation on PdCl(,2)(PhCN)(,2) in aqueous ethanol with added pyridine. This cis metallocycles were formed by a similar displacement reaction on PdCl(,2) in acetonitrile but using a heterogeneous base (K(,2)CO(,3)) and a stoichiometric amount of AgNO(,3). Full …
Polymeric Catechols., Supon Chotiwana
Polymeric Catechols., Supon Chotiwana
LSU Historical Dissertations and Theses
Polymeric catechols have been synthesized by two general procedures: (a) incorporation of catechol synthons into preformed polymers, or (b) synthesis and polymerization of a monomer containing a formal-protected catechol substituent. The utilization of condensation polymers containing oxy-phenylene repeat units as alternative supports to polystyrene has been evaluated. The techniques of functionalization of the polymers via chloromethylation 1,4-bis(chloromethoxy)butane were highlighted. The effects of concentration, reaction time, and types of Lewis acid catalysts on the extent of chloromethylation were studied. Incorporation of catechol synthons such as 1,3-benzodioxole, 2,2-dimethyl-1,3-benzodioxole, or o-phenylene carbonate into the polymeric matrices having oxy-1,4-phenylene backbone via the Friedel-Crafts reactions …
Structure Elucidation And Chemistry Of Sesquiterpene Lactones From The Subtribe Melampodiinae., Arcelio Jose Malcolm
Structure Elucidation And Chemistry Of Sesquiterpene Lactones From The Subtribe Melampodiinae., Arcelio Jose Malcolm
LSU Historical Dissertations and Theses
The isolation and structure determination of seven new cis-1(10), cis-4-germacranolides, longicornin A-D, from Melampodium longicorne, 9-desacetoxymelcanthin F from Polymnia maculata, and 9-desacetoxymelcanthin A and 9-desacetylmelcanthin B from M. leucanthum is described. The structure, configuration and conformation of the new compounds were determined by chemical transformations, and spectral correlation using NMR, MS and CD. The single crystal X-ray diffraction of longicornin A represented the first crystal structure of a germacra-cis-1(10), cis-4-dien-trans-6,12-olide. Sodium borohydride reduction of 2(beta)-hydroxy-cis,cis-germacranolides formed rearrangement products under loss of the ester function at C-9 and double bond migration from 1(10) to the 9(10) position, via S(,N)2' reactions involving …
Synthesis And Characterization Of Ketone And Ketal Coronands Containing 2,6-Pyridino And/Or 6,6'-(2,2'-Dipyridino) Subunits., Hellen Connie Rowland Taylor
Synthesis And Characterization Of Ketone And Ketal Coronands Containing 2,6-Pyridino And/Or 6,6'-(2,2'-Dipyridino) Subunits., Hellen Connie Rowland Taylor
LSU Historical Dissertations and Theses
Pyridyllithium reagents were employed in the synthesis of 6-substituted bis(2-pyridyl) ketones and 6,6'-disubstituted 2,2'-dipyridines. The resulting compounds were used in the attempted preparation of pyridine analogues of simple corrins. Coronands were generated from 2,2-bis(6'-bromo-2'-pyridyl)-1,3-dioxolane. Hydrolysis of the protecting dioxolane gave the corresponding ketone coronands, which could be reduced to macrocyclic carbinols with sodium borohydride. Although these compounds would not complex transition metal ions, several were observed to sequester neutral molecules. In particular, the hexaethylene glycol ketone coronand was proven by X-ray diffraction methods to encircle a molecule of water. Electron-poor aromatic ketones were discovered to decarbonylate under mild, basic conditions. …