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標題: Chemoselective deacylation of functionalized thioesters catalyzed by Dy(OTf)3 4-Acetoxybenzyl carbonate: Lanthanide(III) metal-catalyzed removable orthogonal protecting group of carbohydrates
(1) 利用三氟甲烷磺酸鏑催化具化學選擇性去除硫乙醯基之開發 (2) 利用三價鑭系金屬催化醣類分子正交性保護基之設計
作者: Jiun-Rung Guo
關鍵字: 論文;中興大學;Thesis;National Chung Hsing University
In the first part of this thesis, we reported an efficient and convenient synthetic approach to thioacetate deprotection by utilizing Dy(OTf)3 catalyst under mild heating conditions. Compared with traditional method, our reaction conditions are milder catalytic systems, and reduced byproduct such as disulfide bond formation. We also investigated the feasibility of chemoselecctive S-deacetylation of functionalized thioester molecules and resulted in good yields. Furthermore, the Dy(OTf)3 is an environmentally friendly catalyst, and we have conducted a recyclable used strategy for S-deacetylation.
The second part of this thesis, we have developed the 4-acetoxybenzyl(4-nitrophenyl)carbonate (ABNPC) as a new orthogonal protecting group for carbohydrate. The ABNPC group is readily prepared starting from the commercially available, inexpensive 4-hydroxybenzyl alcohol. The ABNPC group can be selective removed using ytterbium(III) trifluoromethanesulfonate without affecting a series of common protecting groups. According to experimental results, this reaction is mild condition without other additives, and orthogonal with commonly used benzoyl, benzyl, p-methoxybenzyl and benzylidene groups.

本篇論文的第一部分,是利用三氟甲烷磺酸鏑作為催化劑,在溫和的條件下除去硫乙醯基。相較於傳統的方法,本研究開發之反應條件是金屬催化的系統,所以不需要過量或等量的反應試劑來進行,而且反應過程中能降低副產物的生成,例如雙硫鍵的形成。另外,本論文也探討利用開發之方法去進行化學選擇性移除硫乙醯基,其中對於結構中含有叔丁氧羰基 (Boc)、對甲氧基芐基 (PMB)、苯甲醯基 (Bz),甚至是乙醯化醣體分子,都具有良好的化學選擇性來移除硫乙醯基。最後本研究也探討催化劑的回收再使用策略,其結果顯示催化劑經過回收再使用,依然保有其活性。
而本篇論文之第二部分,是引入一4-acetoxybenzyl(4-nitrophenyl)carbonate (ABNPC) 基團當作醣體分子之正交性保護基。在本研究中,是使用三氟甲烷磺酸鐿催化選擇性移去ABNPC保護基。其原理是藉由先選擇性去除位於苯基 (Phneyl) 位置乙醯基,再經由電子轉移而脫去分子二氧化碳後,而將此ABNPC保護基去除。除此之外,我們也試圖嘗試在醣體結構中引入其它常見之保護基,例如苯甲醯基、苄基、對甲苯甲氧基、及縮醛等,並在催化條件下進行選擇性去保護,由結果顯示,大部分之常見保護基並無受到影響,證明此ABNPC保護基具有其正交性之特性。
Rights: 同意授權瀏覽/列印電子全文服務,2020-08-22起公開。
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