reactions.
6 It can therefore be envisaged that 4 and 5 will be useful intermediates and we
describe their preparation on multi-gram scale herein.
The treatment of 1 with 4-methoxybenzaldehyde as described previously by Bergmann and
Zervas gave 2. Next the benzoylation of 2 using benzoyl chloride in pyridine gave 3. The imine
in 3 was hydrolysed under acidic conditions to give the salt 4, which is prepared without the
need for chromatography in any of the steps starting from 1. Finally, the amine is acetylated
with acetyl chloride to give the perbenzoyated-GlcNAc. All products crystallized readily and
were fully characterized and the sequence was carried out in multigram scale. Only in the final
step was chromatography used in order to obtain a sample for analytical purposes.
Experimental
General Methods. NMR spectra were recorded using Agilent Spectrometers at the
indicated frequencies. Chemical shifts in
1 H-NMR spectra are reported relative to internal
Me4Si (δ 0.00) in CDCl3 or DMSO-d6 (δ 2.49) and CDCl3 (δ 77.00) or DMSO-d6 (δ 39.97 ppm)
for
13 C. NMR spectra were processed and analysed using MestReNova software.
1 H-NMR
signals were assigned with the aid of gDQCOSY.
13 C NMR signals were assigned with the aid
of gHSQCAD, DEPT and APT experiments. Coupling constants are reported in Hertz. Mass
spectral data were obtained using a Waters LCT Premier XE Spectrometer, measuring in both
positive and/or negative mode as, using MeCN as solvent. Optical rotations were determined
at the sodium D line at 20 °C with a Schmidt & Haensch Unipol L 1000 polarimeter, using
chloroform and DMSO as solvents. The solvents ethanol, methanol, acetone and Et2O were
used as obtained from Sigma-Aldrich. Solutions in organic solvents were dried with anhydrous
Na2SO4 and concentrated at reduced pressure.
2-Amino-2-deoxy-N-(4-methoxybenzylidene)-D-glucopyranose (2). D-Glucosamine·HCl 1
(15.3 g, 71.0 mmol) was added to 1 M NaOH (80 mL) and the mixture was stirred vigorously
6 It can therefore be envisaged that 4 and 5 will be useful intermediates and we
describe their preparation on multi-gram scale herein.
The treatment of 1 with 4-methoxybenzaldehyde as described previously by Bergmann and
Zervas gave 2. Next the benzoylation of 2 using benzoyl chloride in pyridine gave 3. The imine
in 3 was hydrolysed under acidic conditions to give the salt 4, which is prepared without the
need for chromatography in any of the steps starting from 1. Finally, the amine is acetylated
with acetyl chloride to give the perbenzoyated-GlcNAc. All products crystallized readily and
were fully characterized and the sequence was carried out in multigram scale. Only in the final
step was chromatography used in order to obtain a sample for analytical purposes.
Experimental
General Methods. NMR spectra were recorded using Agilent Spectrometers at the
indicated frequencies. Chemical shifts in
1 H-NMR spectra are reported relative to internal
Me4Si (δ 0.00) in CDCl3 or DMSO-d6 (δ 2.49) and CDCl3 (δ 77.00) or DMSO-d6 (δ 39.97 ppm)
for
13 C. NMR spectra were processed and analysed using MestReNova software.
1 H-NMR
signals were assigned with the aid of gDQCOSY.
13 C NMR signals were assigned with the aid
of gHSQCAD, DEPT and APT experiments. Coupling constants are reported in Hertz. Mass
spectral data were obtained using a Waters LCT Premier XE Spectrometer, measuring in both
positive and/or negative mode as, using MeCN as solvent. Optical rotations were determined
at the sodium D line at 20 °C with a Schmidt & Haensch Unipol L 1000 polarimeter, using
chloroform and DMSO as solvents. The solvents ethanol, methanol, acetone and Et2O were
used as obtained from Sigma-Aldrich. Solutions in organic solvents were dried with anhydrous
Na2SO4 and concentrated at reduced pressure.
2-Amino-2-deoxy-N-(4-methoxybenzylidene)-D-glucopyranose (2). D-Glucosamine·HCl 1
(15.3 g, 71.0 mmol) was added to 1 M NaOH (80 mL) and the mixture was stirred vigorously