Synthesis of a Glycosylphosphatidylinositol (GPI) Fragment as a Potential Substrate for Mannoprotein Transglycosidases

A glycophosphatidylinositol tetrasaccharide fragment was synthesized to mimic the core features of primary model, that of Saccharomyces cerevisiae. The salient feature of this approach is centered on the quick access to various α-1,2- and α-1,6-mannosyl and α-1,4-glycosyl linkages by using simple glycosylation and protective-group techniques. 1D and 2D-J-resolved NMR spectroscopy was used to verify the α-configuration of the new linkages. The tetrasaccharides obtained in this work are useful for examining fungal cell-wall glycoprotein cross-linking by transglycosidase enzymes for antifungal drug development.

A Fascination with 1,2-Diacetals

1,2-Diacetals are readily prepared, rigid structural motifs that provide a wide range of opportunities for applications in natural product assembly. These uses encompass selective 1,2-diol or alpha-hydroxy acid protection, enantiotopic recognition and desymmetrization methods, chiral memory applications, and reactivity control in oligosaccharide synthesis, as well as functioning as templating components, chiral auxiliaries, and building blocks. 1,2-Diacetals are often more stable and lead to products with enhanced crystallinity compared to their five-ring acetonide counterparts. Many 1,2-diacetals have favorable NMR parameters, which facilitate structural assignment, particularly during asymmetric reaction processes.