Researchers of the Zelinsky Institute have developed a method for contraction of the pyranose cycle of various glycosides

Monosaccharides in the furanose form are often found in the cell wall polysaccharides of pathogenic fungi (Aspergillus fumigatus) and bacteria (Mycobacterium tuberculosis). For effective diagnosis and treatment of diseases caused by these microorganisms, a detailed study of these carbohydrates is necessary. That is why the search for reliable methods for the synthesis of selectively functionalized O-furanosides is an important area of modern carbohydrate chemistry.

Researchers from the Glycochemistry Laboratory of the ZIOC have developed a method for ring contraction of O-glycopyranosides and hemiacetals containing bulky silyl groups into partially protected O-glycofuranosides under mild acidic conditions (TFA/CH2Cl2). As in the case of ring contraction of S-glycopyranosides (Abronina et al. Org. Lett. 2018, 20, 6051; Abronina et al. ChemistrySelect 2021, 6, 6223), the presence of bulky silyl substituents is a key factor in the rearrangement of O-glycopyranosides, as well as the influence of the nature of the aglycon. Presumably, the process occurs due to the protonation of the oxygen of the cycle, followed by endocyclic cleavage of the C1–O5 bond of the pyranose ring and recyclization. The proposed efficient method for the synthesis of various furanosides will be useful for the synthesis of biologically significant oligosaccharides.

Source:

Polina I. Abronina, Nelly N. Malysheva, Alexander I. Zinin, Maxim Y. Karpenko, Natalya G. Kolotyrkina, Leonid O. Kononov Trifluoroacetic acid-promoted ring contraction in 2,3-di-O-silylated O-galactopyranosides and hemiacetals Synlett, 2022, accepted manuscript. DOI: 10.1055/a-1730-9458.