利用酵素對雙醣酯類衍生物的選擇性水解反應之研究

Abstract

蔗糖（Sucrose）是自然界中存在最普遍的雙醣，其多種衍生物分別俱有如甘味料，驅蟲劑及化妝品等功效，但因其俱有8個化性相似的羥基．造成合成時的困難。 基於不同水解酵素對同一基質可以有不同選擇性之假設，我們將蔗糖的 8 個羥基以乙醯基保護形成 Sucrose Octaacetate ，再以不同的酵素水解之，發現在 8 種可能的 Sucrose Heptaacetate 異構物中可經由不同的酵素水解產生其中的 6 種、更甚者其中三種不同的1°羥基也可被分別區辨獲得，這在傳統化學反應裡是很難達成的。 為了將此一發現推廣到其他的雙醣，我們接下來選擇了麥芽糖（Maltose ）和纖維二糖（Cellobiose ）的Octaacetate 為基質並用可以區辨 Sucrose三個1°羥基的三種酵素分別水解，但是發現在 Sucrose 所擭得的結果並不能推廣至此，加以此二化合物的 N ．M．R光譜較為複雜，故仍待進一步研究。 我們企圖運用 Sucrose Octaacetate 的酵素水解反應的衍生物，來作為合成一些俱有生物活性的分子的起始物，初步選定的為 4 . 1 ' , 4 ' , 6 ' tetrachloro一4 , 1 ' , 4 ' , 6 ' tetradeoxy-galacto-Sucrose 和 3 , 3 ' , 4 , 6 , tetra-O-acylated Sucrose ester ，合成的工作均已在進行中；此外，我們亦噹試配合最近化學上對α，βLinkage 合成上的發展合成 Hepta-saccharide之Oligosaccharin 作為 Chemo-enzymatic oligo-saccharide synthesis 的嚐試。

Sucrose is the most aboundant disaccharide in nature and many of its derivatives have properties such as sweeters, insectifugs and cosmetics. However , These useful molecules are difficult to synthesize because of the existances of eight hydroxyl groups of similar properties in sucrose. Basing on the assumption that different enzymes will have different selectivities toward the same substrate , the eight hydroxyl groups of sucrose are protected by acetyl groups to form sucrose octaacetate and hydrolyzed by different enzymes . We find that six of the eight sucrose heptaacetate isomers can be formed from the hydrolysis of sucrose octaacetate by different enzymes. Moreover , the ester bonds formed from three different primary hydroxyl groups can be distinguishd specifically and this result is hard to achieve by classical chemical methods We also use the three enzymes that can distinguish the three hydroxyl groups of sucrose to hydrolyze maltose octaacetate and cellobiose octaacetate in order to extend this approach to other disaccharides. However , It does not well in these two disaccharide octaacetate in a preliminary study and it still need a further investigation because the NMR spectra of these two substrates are more complex The works using some sucrose esters derivatives from the enzymatic hydrolysis reactions as the starting materials to synthesize some useful molecules such as 4,1’,4’,6’ tetrachloro-4,l’,4’,6’ tetradeoxy-galacto-sucrose and 3,3’,4,6,tetra-O-acylated sucrose ester are underway. We also try to combine the recent development for the α, βglycoside linkage control with the enzymatic method to synthesize the oligosaccharin chemoenzymatically.