Oligosaccharides have a variety of versatile biological effects, but unlike peptides and oligonucleotides, investigation of the roles of oligosaccharides is not easy. Since biosynthesis of oligosaccharides does not comply with direct genetic control, their isolation from natural sources and biotechnological preparation are complicated, due to the heterogeneous composition of raw carbohydrates. Oligosaccharide synthesis is needed for the establishment or confirmation of the structure of natural glycocompounds. Also, synthetically prepared, defined oligosaccharides and their derivatives are becoming increasingly important tools for many biological and immunological research projects. The key step of oligosaccharide synthesis involves glycosylation, a reaction that builds glycosidic bonds. Usually, construction of 1,2-trans-bonds is easy, and therefore, this reaction can even be included into automated syntheses. At this time, installation of the 1,2-cis-bond remains simultaneously frustrating and compelling. In our and other laboratories, a strategy of α-selective (1,2-cis) glycosylation, relying on remote anchimeric assistance with acyl groups, is studied. The state of the art in this work is summarized in this review.
3-Aminopropyl α-(1→3)-pentaglucoside, a fragment of α-(1→3)-glucan of the cell wall of Aspergillus fumigatus, has been synthesized in a blockwise approach. The application of mono- and disaccharide N-phenyltrifluoroacetimidates bearing a stereodirecting 6-O-benzoyl group was essential for stereoselective α-glucosylations. In the products, p-methoxyphenyl and levulinoyl groups served as orthogonal protecting groups for the anomeric position and 3-OH group, respectively. Their removal from shared blocks led to donors and acceptors that were used for the synthesis of pentasaccharides. Coupling of free α-(1→3)-pentaglucoside with biotin and bovine serum albumin (BSA) gave glycoconjugate tools for mycological studies. Immunization of mice with the BSA conjugate induced the generation of antibodies that recognize α-(1→3)-glucan on A. fumigatus cell wall and distinguish its morphotypes. This discovery represents a first step to the development of a diagnostic test system and a vaccine to detect and fight this life-threatening pathogen.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.