Uivalents of donor 5 proceeded smoothly to offer the -(28)-linked disaccharide

Uivalents of donor 5 proceeded smoothly to offer the -(28)-linked disaccharide 16 in 62 yield. Again, no isomer was observed. The moderate yield is due to concomitant migration of the 7-O-acetyl protecting group towards the major 8-OH group forming a regioisomer which was not glycosylated below these reaction conditions. The glycosylation on the corresponding 8-OH alcohol (derived from 15 by F- remedy) gave a equivalent yield (64 ), although bulkier silyl guarding groups (8-O-TBDMS, 7,8-O-TIPDS) substantially lowered the isolated yield. The extraordinary glycosylation properties of five prompted us to apply the donor for the onepot synthesis of a branched Kdo trisaccharide, which corresponds to an LPS antigen of Chlamydophila psittaci and serves as a species-specific marker.[26] Certainly, glycosylation of unprotected tetraol 19 with 2.4 equivalents of donor five proceeded while getting heterogeneous – in a remarkably regioselective reaction, which allowed to isolate the target trisaccharide 20 in 58 yield (Scheme three). As minor by-product the branched -(24)[(27)]-linked Kdo trisaccharide was isolated in 7 yield. Processing of 20 as described for the disaccharides gave 21 and 22 which was then deblocked to afford the branched Kdo trisaccharide 23.Anabasine web This simple notion was additional extended to iterative oligosaccharidesynthesis, demonstrated for the linear Kdo trisaccharide 31, representing the family-specific Chlamydia epitope (Scheme 4). Just after applying the 8-O-silyl protected glycal ester 24 as glycosyl acceptor, the resulting disaccharide 25 was treated likewise by iodoacetoxylation and reaction with HF-pyridine to afford the bis-iodo disaccharide donor 27. Thus, the glycal moiety as in 25 serves as a latent guarding group for the anomeric position, which may perhaps subsequently be activated.Lamivudine supplier Interestingly, BF3.PMID:24406011 Et2O was not capable of advertising the subsequent coupling step with glycosyl acceptor ten, however, TfOH-catalyzed (0.15 eq.) coupling offered trisaccharide 28 stereospecifically within a good yield (73 ). Acetylation and dehalogenation of 28 followed by worldwide deprotection of 30 afforded the target trisaccharideEurope PMC Funders Author Manuscripts Europe PMC Funders Author ManuscriptsChemistry. Author manuscript; available in PMC 2016 February 26.Pokorny and KosmaPage31. The 1H and 13C NMR data of the deprotected di- and trisaccharides 14, 18, 23 and 31 are in full agreement with published data of chlamydial oligosaccharides.[27]ConclusionsIn conclusion, the simply accessible 3-iodo-2-fluoride Kdo donors allow a really effective and -specific glycosylation of diverse Kdo glycosyl acceptors to create biomedically vital LPS fragments. Along with the exquisite -selectivity, the axial iodosubstituent substantially suppressed the elimination towards the glycal side-product (Table 1). Sequential iteration of this standard idea might be combined with variable safeguarding group patterns, hence considerably expanding the scope in the presented function towards other biomedically crucial Kdo-antigens.Europe PMC Funders Author Manuscripts Europe PMC Funders Author ManuscriptsExperimental SectionGeneral approaches All purchased chemical substances have been applied without further purification unless stated otherwise. Solvents had been dried more than activated four (CH2Cl2, DMF, pyridine, cyclohexane) molecular sieves. 2-Propanol for glycosylation was dried more than 5 molecular sieves for 24 h. THF was straight distilled on 4 molecular sieves shortly before use. Dry MeOH (secco solv) wa.