A new and stereospecific approach to Kdo-containing disaccharides using phenylselenyl triflate

Synthesis of the Core Oligosaccharides of Lipooligosaccharides from Campylobacter jejuni: A Putative Cause of Guillain–Barré Syndrome

“…Consequently, compound 9 was formed from 6 in 77 % yield over three steps. The stereochemical assignment of α‐KDO glycoside was confirmed according to the literature, for which the J 3eq,4ax value (5.0 Hz) in the 1 H NMR spectrum of 7 was almost identical to the value (5.2 Hz) reported for α‐KDO glycosides . Furthermore, comparison of the HMBC spectra of 9α and 9β supported the anomeric stereochemistry of the KDO glycosides; 9β , which has a larger heteronuclear coupling constant ( 3 J C1,H3ax ), showed a stronger correlation between C1 and H3ax than 9α (see the Supporting Information).…”

“…For α‐selective glycosidation of 2,3‐ene derivative 6 (to afford 7 ), phenylselenyl trifluoromethanesulfonate (PhSeOTf) was chosen as a promoter, as Achiwa et al. reported that highly electrophilic PhSeOTf, which was generated in situ by treating phenylselenyl chloride with silver trifluoromethanesulfonate (AgOTf), served as a good α‐directing reagent . After glycosidation, a reduction step was performed by treating 7 with triphenylstannane and 2,2′‐azobisisobutyronitrile (AIBN) to afford desired α‐KDO glycoside 8 with a trace amount of the β isomer, which was difficult to separate from the α isomer at this stage.…”

“…reported that highly electrophilic PhSeOTf,w hich was generated in situ by treatingp henylselenyl chloride with silver trifluoromethanesulfonate( AgOTf), served as ag ood adirectingr eagent. [16] After glycosidation, ar eduction step was performed by treating 7 with triphenylstannane and2 ,2'-azobisisobutyronitrile (AIBN)t oa ffordd esired a-KDO glycoside 8 with at race amount of the b isomer,w hich was difficult to separatef rom the a isomer at this stage. The optimum result was obtained if the glycosidationw as started at À20 8Ca nd the reaction temperature was gradually increased to 0 8C, whereas glycosidations at higher temperatures, starting from 0 8Co rr oom temperature, generated many byproducts.…”

Stereoselective Synthesis of Oligo‐α(2,8)‐3‐deoxy‐D‐manno‐2‐octulosonic Acid Derivatives

“…In 1987, Shiba and co‐workers reported that α‐ketopyranosyl fluoride was an effective donor for the α‐selective glycosidation of KDO 3. Furthermore, in 1989, Achiwa and co‐workers reported that the glycal ester underwent glycosyloxyselenation to provide α‐linked 3‐phenylselenyl‐KDO derivatives 4. The feasibility of these methods was mainly demonstrated by the synthesis of mono‐KDO‐containing oligosaccharides.…”

Anomeric O-acylation of Kdo using alkyl and aryl isocyanates

“…[1][2][3][4][5][6] Up to date, two groups have accomplished the synthesis of an a-Kdo derivative carrying a spacerarm in high yields. [5][6][7] However, these methods have not yet been fully developed as a general conjugation method for chemically synthesized OS containing Kdo at the reducing end.…”