Synthesis of N-substituted Five and Six-membered Iminocyclitols-bearing Sugar Moiety: Strategy Toward the Synthesis of Pseudodisaccharide

Aim and Objective: The efficient synthesis of disaccharide containing iminosugar moiety has a considerable interest in the field of glycoscience. In the present work, we describe a novel and applicable method for synthesis of five and six-membered N-substituted iminosugars attached with sugar moiety (pseudodisaccharides). Materials and Methods: The method of the glycosylation was based on the coupling of iminosugar thioglycoside (glycosyl donors) with partially protected sugars (glycosyl acceptors) in the presence of DMTST as a promoter. 2D COSY, HMQC, HMBC experiments were carried out to assist in NMR signal assignments. The pseudoanomeric configuration was established through NOE experiments and molecular modeling calculations. Results: Two classes of pseudodisaccharides were successfully obtained, five and six-membered N-substituted iminosugars glycosides. The six-membered pseudodisaccharides compounds were produced selectively with only β anomer. The corresponding five-membered pseudodisaccharides were achieved with moderate stereoselectivity. The yields obtained were good. These derivatives of iminocyclitols are thought to be precedents to develop various pseudodisaccharides, novel biologically active compounds, and new functional molecules. Conclusion: According to the results, utilizing iminosugar thioglycosides (1 and 2) as a glycosyl donor in glycosylation reactions is an efficient and highly stereoselective method to prepare (five- and six-membered) iminocyclitols (iminosugars) that bear a sugar moiety. The results will add to the synthesis of the iminosugars derivatives and contribute to make our approach among the few methods able to synthesize iminosugar glycosides.