博士 / 國立清華大學 / 化學系 / 94 / This thesis details an investigation in the use of an abundant and cheap naturally occurring reagent in organic synthesis. Specifically, (-)-��-pinene (14) was used to generate chiral dienophile 28 and the Diels-Alder cycloaddition reactions thereof were investigated. Among the numerous Lewis acids perused, ZnCl2was found to be optimal, giving the Diels-Alder cylcoadduct in high facial selectivity and following the established Diels-Alder cycloaddition rules on selectivity.
The cycloadducts obtained in the above study was further investigated in their utility as substrates for a recently developed reductive alkylation of ��-cyano cycloalkanones as developed in our laboratories. As such, the obtained chiral adducts were subjected to the established reductive alkylation protocol and the resulting alkylation product was elucidated in terms of stereochemistry and scope of alkylating agent. This investigation further broadened the scope of utility of such Diels-Alder adducts towards the generation of structurally complex motifs.
Using the experiences garnered in the above survey, the asymmetric total synthesis of xenitorin B (71) and C (72) was achieved. Central to our total synthesis endeavor was the highly stereoselective Diels-Alder cycloaddition between dienophile 28 and isoprene, a face-selective hydrogenation process as directed by the angular nitrile, and the ring opening of the bridged system as previously developed in our laboratories. As such, the total synthesis of chiral 71 and 72 was achieved in 12 and 13 steps respectively. The details of this and the abovementioned investigations constitute this thesis.
| Identifer | oai:union.ndltd.org:TW/094NTHU5065005 |
| Date | January 2005 |
| Creators | 張文昇 |
| Contributors | 劉行讓 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 112 |
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