A sensitive method using high‐performance capillary electrophoresis (HPCE) is employed to study the electrochemical lactonization of α2,8‐trisialic acid. Analysis shows that the sialyl lactonization of trisialic acid in an acidic aqueous solution (pH 4.2–6) is highly enhanced by a supporting electrical current (30–100 μA). CE results indicate that this electrochemical lactonization with a supporting current is faster than the acid‐catalyzed lactonization in acetic acid. This acceleration in the reaction suggests that the acidity increases close to the Pt electrode and assists the sialyl lactonization during electrolysis. Three lactone species of trisialic acid formed in the acidic aqueous solution were detected with HPCE, and the fully lactonized species were examined with time‐of‐flight mass spectrometry and NMR spectroscopy. The elution order of the lactone isomers obtained from previous report and from this study together reveals a regioselective lactoziation in which the sialyl residue close to the reducing end was more reactive than that close to the nonreducing end.
Treatment of peracetylated glycosides and β‐isopropyl glycosides with halogen in the presence of TESH and BHQ has been found to result in the halogenation and the anomerization, respectively. Peracetylatedglycosides treaded with I2/TESH or Br2/TESH leading tothe formation of corresponding glycosyl halides, and b‐isopropyl glycosidesreacted with Br2/BHQ resulting in the formation of a‐glycosides. The anomerizationof glycosidic bond was considered to be catalyzed by in situ formation of hydrogenbromide from the mixing of Br2/BHQ.
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