α-Mannosidase II (GM-II) belongs to a family of enzymes that takes part in the biosynthesis of complex and hybrid N-glycans. N-Glycans are glycoproteins in which the oligosaccharide moiety is covalently attached to amide group of asparagine residue by N-glycosidic bond. The key functions of the N-glycans in biological processes include growth, differentiation, signal transduction, receptor activation, immune system modulation, protein folding, cellular adhesion and host-pathogen interaction.¹ On the other hand, recent studies showed that N-glycans are present in an increased amount in various types of cancer cells and their metastasis.² Since GM-II plays the important role in N-glycans biosynthesis, the inhibitors of GM-II attract attention as drug candidates for cancer treatment. Based on the structure of two alkaloids, swainsonine³ and mannostatin A⁴, which inhibit GM-II, the structure of potential GM-II inhibitor 8 was proposed by using computational methods.

This contribution describes preparation of polyhydroxycyclopentene 4 (in eight synthetic steps starting from D-lyxose) representing the key intermediate for synthesis of target compound 8.