Resin glycosides are plant glycolipids, which are mainly isolated from convolvulaceous (morning glory family) plants. Though they were formerly studied as the major components of traditional folk medicines, unique biological activities have been recently reported such as cytotoxicity against cancer cells, anitimicrobial activity, and plant growth regulatory effects. Most resin glycosides with bioactivity have a macrolidic structure as a result of intramolecular esterification between a carboxylic group at the aglycon fatty acid and one of the sugar hydroxyl groups. Stimulated by these notable structural and biochemical features, extensive studies on the total synthesis of resin glycosides have been completed. In this review, we describe recent progress in the chemical synthesis of resin glycosides.
Glycoproteins play an important role in biological processes, such as cell recognition, cell adhesion, immunogenic recognition, and so on. Additionally, the carbohydrate moieties of the glycoprotein contribute to the solubility and thermal stability of proteins and to protection against proteolysis (1). In order to study these mechanisms, preparation of glycoproteins is required. In this review, preparation of glycopeptide using conventional chemical and recent manners (chemo-enzymatic method, using of natural source) is described.
The synthetic method, conformation, and bioactivity of the unnatural oligosaccharides whose conformational properties are different from those of natural ones, with or without intention are outlined. In the first section of each chapter, interesting synthetic methods which have been developed recently are introduced. In the second section, the following conformational features are detailed. -1) Oligosaccharide analogs built up of C-glycoside, S-glycoside, or N-glycoside have a more flexible conformation than natural ones. 2) Conformational properties are almost equal to each other between natural oligosaccharides and their analogs containing a pseudosaccharide, such as carbasugar or 5-thiosugar, in which the ring oxygen atom has been replaced with an other atom or atomic group at the nonreducing monosaccharide. 3) Conformationally fixed oligosaccharide analogs have been synthesized so that the global minimum conformation of the natural oligosaccharide was frozen by a cross-bridge, such as a methylene chain. 4) Recent trends are illustrated by the development of oligosaccharide analogs having unnatural conformation. The binding abilities to receptor proteins are investigated in some of these oligosaccharide analogs. However, the abilities are equivalent to or lower than those of natural oligosaccharides in most cases. Though the bound-state conformations of oligosaccharide analogs in receptor proteins are equal to those of natural ones in most cases, some analogs bind to a receptor with a different conformation. The knowledge gained from these studies will provide very important information for the design of oligosaccharide-based drugs
The chemistry of the ganglioside synthesis can be divided into three steps: 1) construction of oligosaccharide backbone, 2) introduction of sialic acid into the oligosaccharide backbone, and 3) coupling of the sialo-oligosaccharide and sphingolipid. In this text, the latter two topics are described, first, as the problems common to all gangliosides, and the first topic as the individual problems specific to each subclass of ganglioside.
The biological importance of the proteoglycan (PG) is increasing along with the elucidation of the biological properties. It is essential to approach it from synthetic chemistry in order to recognize the roles of PG at a molecular level. This review focuses on and generally surveys recent syntheses of glycosaminoglycan (GAG), a glycan part of PG, especially of the oligosaccharide at the linkage region of GAG, chondroitin sulfate, dermatan sulfate, hyaluronic acid and heparin/heparan sulfate.