研究生: |
余怡璇 In-Shan Sir |
---|---|
論文名稱: |
具光學活性的2-Oxo-5a,8a-13, 14, 15, 16-tetranorclerod-3-en-12-oic acid和6b-Acetoxy-2-oxokolavenool之形式上的全合成 A Formal Synthesis of Optically Active 2-Oxo-5a,8a-13, 14, 15, 16-tetranorclerod-3-en-12-oic acid and 6b-Acetoxy-2-oxokolavenool |
指導教授: |
劉行讓
Hsing-Jang Liu |
口試委員: | |
學位類別: |
碩士 Master |
系所名稱: |
理學院 - 化學系 Department of Chemistry |
論文出版年: | 2000 |
畢業學年度: | 88 |
語文別: | 中文 |
論文頁數: | 134 |
中文關鍵詞: | 動力光學分割 |
外文關鍵詞: | kinetic resolution |
相關次數: | 點閱:4 下載:0 |
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本論文報導一種合成 2-oxo-5α,8α-13, 14, 15, 16-tetranorclerod-3-en-12-oic acid ( 54 ) (圖一)和 6β-acetoxy-2-oxokolavenool ( 55 ) (圖一)的改良過程。此改良過程的關鍵步驟是具高鏡像純度的4, 4-雙取代環己烯酮的合成。所採用的方法有兩個途徑,第一個方式是將消旋化合物4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone [(±)-67] (圖一),進行動力學光學分割( kinetic resolution ),希望造成兩個鏡像異構物的分離,而分別得到所要的鏡像化合物。第二個方式是改用雙環內醯□( 87 ) (圖一)為起始物,合成出具高鏡像純度的(S)-4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone [(+)-67] (圖一)。可惜,第一個方法並未達到預期效果,但合成的過程中,我們另外發現一種新的,可用來分離出高鏡像純度的(+)和(-)-trans-2-phenylcyclohexanol ( 94 )的方法。第二個方法則成功的得到具高鏡像純度的化合物(S)-4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone [(+)-67] 及(R)-4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone [(-)-67] (圖一),進而完成 cis-normal-clerodanes 54 和 55,和非天然性的 cis-ent-clerodanes 54 和 55的不對稱形式合成。此合成方法不但簡單,且產率高,所得到的化合物 (-)-67,除了能合成上述天然物 cis-normal-clerodanes 54和55 之外,也可以廣泛的應用在合成其他 cis-normal-clerodane類的雙□天然物,如圖十三所示。這些研究內容的說明,將詳述於本論文。
圖一
This thesis describes the formal asymmetric synthesis of 2-oxo-5a,8a-13,14,15,16-tetranorclerod-3-en-12-oic acid (54) and 6b-acetoxy-2-oxokolavenool (55) (Figure 1). The efficient synthesis of (R)-4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone [(-)-67], a common intermediate in a previously reported synthesis of both 54 and 55, in an asymmetric manner was the key concept in this approach. Towards this end, two approaches were investigated: enzymatic kinetic resolution and asymmetric synthesis via Meyer's b-lactam approach to 4,4-disubstituted 2-cyclohexenones. In the first approach, kinetic resolution of a racemic mixture of 4-(2-benzyloxyethyl)-4-methyl-2-cyclohexenone as mediated by lipase AK did not result in a sufficiently high level of asymmetric resolution. However, during our investigations, we developed a new procedure to effectively resolve a racemic mixture of 2-phenylcyclohexanol (94) into its individual chiral forms quantitatively. In the approach using Meyer's b-lactam ([2S-(2a,3b,8ab)]-(+)-hexahydro-3-(hydroxymethyl)-8a-methyl-2-phenyl-5H-oxazo-lo[3,2-a]pyridin-5-one, 87) as starting material, compound (-)-67 was realized in excellent optical and synthetically useful yields. The enantiomer of (-)-67, compound (+)-67, was also synthesized via this chemical approach in excellent optical and synthetically useful yields. Compound (+)-67 was further elaborated to Diels-Alder adducts (+)-70 and 92 containing the core decalin structure of cis-ent-clerodane natural products. The details of our investigations are described in this thesis.
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