Heterocycles are privileged structural motifs found in many natural products and biologically active compounds. Given the prevalence of this structural unit, there has been considerable interest and challenge in developing methods for construction optically pure heterocycles in organic synthesis and pharmaceutical chemistry. The skeleton of hydronaphthalene and indole are pervasive structural motifs in the pharmaceutical drugs that exhibit various bioactivities. This dissertation is mainly focused on the development of transition-metal-catalyzed asymmetric functionalization of alkenes, including the hydroselenation and hydroamination of various oxa/azabicyclic olefins for the synthesis of bioactive compounds and structural modification of oleanolic acid. An efficient rhodium catalytic system consisting of Rh(COD)2OTf/(S)-xyl-Binap, and n-Bu4NI was developed for the asymmetric hydroselenation of various oxa/azabicyclic olefins with diaryl diselenides instead of the unstable, malodorous selenol compounds. Under these reaction conditions, a wide range of heterobicyclic alkenes produced selenol containing hydronaphthalene derivatives in high yields (up to 96%) along with excellent enantioselectivities (up to 97%), overcoming the self- promoted racemic hydroselenation. The exo-configuration of the exclusive addition product was confirmed by X-ray crystal structure analysis. The strategy has also been applied to the kinetic resolution of unsymmetric oxabenzonorbornadiene. Further, these selenium compounds can catalyze the oxidative coupling reaction of 2-naphthols. Then, for the synthesis of trans 1-indolyl dihydronaphthalenols, a highly enantioselective Rh/Pd dual-metal sequentially catalytic system was revealed through intermolecular and intramolecular cascade hydroamination in the reaction of oxabenzonorbornadienes with 2-alkynylanilines. The exclusive trans-configuration of 1-(2-phenyl)indolyl dihydronaphthalenol was identified by X-ray crystal analysis. Various substituents, such as aryl, heteroaryl, alkyl, and silyl groups on alkynyl starting material can be used as compatible nucleophiles in the reaction to give excellent iii enantiomeric excesses (up to 99%) with good yields (up to 88%) under mild conditions. The reaction can be performed on a gram scale, while the indole derivatives could be transformed at the hydroxyl and indolyl funtionalities. The in silico and in vitro screening showed that the novel 1-indolyl dihydronaphthalenol products can serve as potential lead compounds for treating inflammation disease. At last, a series of functional groups, including carboxyl, phosphate, sulfone, triazole, tertiary amine, and glycosyl have been incorporated into oleanolic acid to improve its water solubility. A wide range of their derivatives have been obtained, and it was found that carboxyl salt, phosphate salt, and sulfonate salt contribute to the increase of the solubilities in water; up to 8 g/L was gained for carboxylate salt, which also provides the possibility to improve the bioavailability of these compounds
| Identifer | oai:union.ndltd.org:hkbu.edu.hk/oai:repository.hkbu.edu.hk:etd_oa-1872 |
| Date | 25 August 2020 |
| Creators | Li, Sifeng |
| Publisher | HKBU Institutional Repository |
| Source Sets | Hong Kong Baptist University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Open Access Theses and Dissertations |
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