Synthesis of branched heterooligosaccharides related to Aspergillus galactomannan containing short Galf side chains

The members of a widespread Aspergillus fungi genus cause various diseases including the invasive aspergillosis with high morbidity and mortality rates, especially for immunosuppressed patients. One of the main carbohydrate structures on the surface of their cell wall is the galactomannan (GM) which is used in diagnostic kits for the detection of specific types of aspergillosis. However, limited specificity of currently available test systems urges the need for their further improvement. Herein we report the first synthesis of branched heterosaccharides related to GM and containing α-(1→2)-/α-(1→6)-linked tetramannoside backbone chain bearing one galactofuranoside unit or its β-(1→5)-linked dimer. The preparation of conjugates of the obtained spacered oligosaccharides with BSA is also performed to produce tools for the assessment the specificity of anti-Aspergillus immune response and to select antibodies suitable for the development of novel diagnostic kits that may discriminate distinct types of aspergillosis.