碩士 / 國立清華大學 / 化學系 / 87 / This thesis describes a modified Robinson annelation process, which facilitates the preparation of a,a-disubstituted b,g-unsaturated ketones of general type 19 with complete regiocontrol, and the application of this modification to the synthesis of the marine natural product nanaimoal (33). The modified Robinson annelation makes use of the lithium naphthalenide induced reductive alkylation of g-cyano a,b-unsaturated ketones 18 as the key step. This type of cyano enones can be readily prepared from the corresponding a-cyano ketones 17 using the conventional Robinson annelation procedure (i.e. Michael addition followed by aldol condensation). Treatment of cyano enones 18 with lithium naphthalenide followed by trapping of the ensuing enolates with a suitable alkylating agent gave rise to the corresponding enones 19, which can not be easily prepared by the conventional Robinson annelation reaction.
Towards the synthesis of nanaimoal (33), the known dicyano aldehyde 58 was subjected to treatment with methylenetriphenyl-phosphorane to give cyano ketone 59 as a result of concomitant Wittig reaction and Thorpe-Ziegler cyclization. This compound was then converted to ketone 61, using the newly developed modification of the Robinson annelation reaction. Wolff-Kishner reduction of 61 gave the known diene 57, which had previously been converted to nanaimoal (33) in two steps. Thus, a formal total synthesis of the marine natural product has been achieved.
| Identifer | oai:union.ndltd.org:TW/087NTHU0065040 |
| Date | January 1999 |
| Creators | Chia-Liang Tai, 戴嘉良 |
| Contributors | Hsing-Jang Liu, 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 | 210 |
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