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.

Acknowledgement. Financial support of this work by the Slovak Grant Agency (VEGA grant nos. 2/0064/15 and 2/0024/16) and Slovak Research and Development Agency (APVV grant no. APVV-0484-12) is gratefully appreciated. This contribution is the result of the project implementation: Centre of Excellence for Glycomics, ITMS 26240120031, supported by the Research & Development Operational Programme funded by the ERDF.

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2. Vasconcelos-dos-Santos, A.; Oliveira, I. A.; Lucena, M. C.; Mantuano, N. R.; Whelan, S. A.; Dias,W. B.; Todeschini, A. R. Front. Oncol. 2015, 5   (138), 1.
3. Pyne, S. G. Curr. Org. Synth. 2005, 2, 39.
4. Vasella, A.; Hu, G. Helv. Chim. Acta 2004, 87, 2405.