Chirality Analysis of Mannnopyranose in 35. Compounds
35 (each 1 mg) were treated with 4 M TFA at 110 C for 4 h to give
their acid hydrolysates. The acid hydrolysate of each compound was
then derivatized with 2,3-naphthalenediamine using molecular iodine as
catalyst to obtain the fluorescent naphthimidazole derivative of the
mannopyranose (manno-NAIM) as previously reported.11 The fluorescent
product was further applied for chiral resolution using the
ligand exchange capillary electrophoresis (LECE) method.18,19 Electrophoretic
experiments were carried out using a Beckman Coulter
capillary electrophoresis system (model P/ACE MDQ, USA) equipped
with a photodiode array UV detector. The background electrolyte
in the electrophoretic experiments was composed of 10% acetonitrile,
200 mM sulfated-R-CD, and 200 mM phosphate buffer (pH 3.4).
An uncoated fused-silica capillary (30/40.2 cm 50 μM) was used.
The capillary temperature was kept at 30 C, and the analyte was
detected by UV absorption at 254 nm. The sample loading is set at
40 ppm at 0.5 psi, 3 s for each injection. The D- and L-forms of manno-
NAIM were used as standards and were enantioseparated in the above
LECE system individually. The retention times of L- and D-form
standards were 21.05 and 23.15 min, respectively. Under the same
conditions, the retention time of the manno-NAIM originating from
35 was 23.15 min. Thus, the mannopyranose in 35 was determined
to be the D-form.