Synthesis Of6,6’-S-Trehalose Dimycolates And Selective Removal Of Thioacetyl Group With Aqueous Nasme Solution

The dissertation describes the first synthesis of6,6’-S-linked trehalose dimycolates, and investigations on the selective removal of thioacetyl group with aqueous NaSMe solution. Three chapters are included in this thesis:Chapter One is the preface, including two parts:firstly, the chemistry and various biological functions of trehalose glycolipids are summarized with the emphasis on the trehalose6,6’-dimycolates. The recent development of synthetic methods and the important biological activity of this type of trehalose glycolipids are presented. Secondly, an overview of the preparation of thioacetyl sugars and selective deprotection of thioacetyl group is described.Chapter Two covers the synthesis of the title compounds. The synthesis of the key building block, S-linked trehalose, was first optimised and it was obtained in very high yield and excellent stereoselectivity. Next, the selective hydrolysis of primary O-TMS protecting group of per-trimethylsilylated S-trehalose was investigated employing a series of different conditions. HOAc turned out to be the optimal for this regioselective deprotection. Subsequently, the above intermediate was used to construct the S-trehalose dimycolates.Chapter Three describes the selective removal of thioacetyl group with aqueous NaSMe in the presence of O-acetyl groups. The mild conditions, the high yields and the lower cost of the aqueous reagent are attractive features in this procedure, compared with the literature methods.