Synthetic Study of Sulfatides

硫苷脂的生理作用目前尚不清楚。它们是归为鞘糖脂的化合物，其特征在于分子中具有非常极性的磺酸部分。硫苷脂通常是几种化合物的混合物。硫苷脂的这种结构复杂性是由于其脂质部分神经酰胺的复杂性，神经酰胺由一种称为鞘氨醇的碱和一种酸组成。后者都是不同碳链长度的化合物的混合物。因此，硫苷的复杂性主要归因于鞘氨醇和酸性部分。为了合成化学纯的硫苷脂，因此有必要合成化学纯的鞘氨醇。硫苷脂合成中的另一个问题是在糖中区域选择性地引入磺酸基团（即，本论文针对这两个问题进行了研究，并阐明了以下几点：（1）探索了一种通过糖苷的区域选择性单氧化来区域选择性和立体选择性合成氨基糖的新方法。从而建立了从易得的木糖或葡萄糖合成氨基糖的实用方法。应用这种新方法，经济地合成了一种著名的葡萄糖苷酶抑制剂--野尻霉素。(2)将通过上述方法获得的4-氨基-4-脱氧-阿拉伯糖转化为各种鞘氨醇的“手性共同中间体”。以该中间体为原料合成了C-18鞘氨醇。(3)半乳糖部分区域选择性引入磺酸基：β-半乳糖苷衍生物经二丁基氧化锡和氯磺酸硫酸化，区域选择性地得到3-磺酸衍生物。(4)用光度离子色谱法（PIC）对糖磺酸酯进行了分析。这是将HPLC应用于此类高极性且不可UV降解的化合物的实例。

The physiological role of sulfatides is not clear at present. They are the compounds grouped to sphingo-glycolipids, and are characterised in having very polar sulfonic acid moiety in the molecule. Usually sulfatide is obtained as a mixture of seversal compounds. This structural complexity of sulfatide is due to the complexity of its lipid part, ceramide, which is constitued of a base, called sphingosine, and an acid. Both of the latters are the mixtures of the compounds of various carbon chain length. Therefore, the complexity of sulfatide is mainly attributable to that of sphinogosine and the acid part. In order to synthesize chemically pure sulfatide, it is therefore necessary to sythesize chemically pure sphingosine. This is one problem in sulfatide synthesis.Another problem in sulfatide synthesis is the regio-selective introduction of a sulfonic acid group in the sugar (i.e.,galactose)portion.The present study was done for solving these two problems, and clarified the followings:(1) A new method of regio- and stereo-selective synthesis of amino-sugars via regioselective mono-oxidation of glycosides was exploited. Thus, the method of practical synthesis of aminosugars from easily available xylose or glucose was established. By application of this new method, an antibiotic, nojirimycin, a famous glucosidase inhibitor, was synthesised economically.(2) 4-Amino-4-deoxy-arabinose obtained by the above method was converted to a "chiral common intermediate" to various sphingosines. Synthesis of C-18 sphingosine from this intermediate was described.(3) Regioselective introduction of sulfonic acid group into the galactose portion: Sulfatation of beta-galactoside derivatives by dibutyltin oxide and chlorsulfonic acid gave 3-sulfonic acid derivatives regioselectively.(4) Sugar sulfonic acid esters were well analysed by using photometric ion chromatography (PIC). This is an example of application of HPLC to such highly polar and not UV absorbale compounds.