S.-M. Wang et al. / Carbohydrate Research 346 (2011) 203–209
209
3.2. Reaction of DBTO with model compound 1 in MeOH-d4
DBTO (16 mol), 1 (17 mol), and MeOH-d4 (2 mL) were added
to an NMR tube, and then the tube was sealed by fusing in air. The
tube was heated in a water bath at 66 °C, and the reaction was
monitored by 400 MHz 1H NMR spectroscopy.
4. Conclusions
l
l
It is deduced that it is the dimeric 1,3-dimethoxytetrabutyldis-
tannoxane is produced at first by the reaction of DBTO with MeOH,
then the tetraorganodistannoxane reacts with the acetylated glu-
coside to produce glucoside organotin complex intermediates. Fi-
nally, the complex intermediates are hydrolyzed easily, which
leads to the free-OH glucoside and organotin acetate derivatives.
It is the neighboring group participation that accelerates the
deprotection of the 3-OAc, 4-OAc, and 2-OAc groups, and the inten-
sity of action of the 2-OAc group is less than that of the 3-OAc and
4-OAc positions. Because of the lack of neighboring group partici-
pation, the reaction rate of the 6-OAc is much lower than that of
the 3-OAc, 4-OAc, and 2-OAc groups. So, the acetyl groups of the
sugar moieties of glucosides can be selectively cleaved by adjusting
the reaction time, temperature, or solvent as in our previous
studies.8,9
3.3. Reaction of DBTO with model compound 1 in MeOH
Equimolar amounts of DBTO (0.6 mmol) and 1 were heated un-
der reflux in dry MeOH (30 mL) until 1 disappeared as determined
by TLC monitoring (about 130 min). Aliquots (5 mL) of the reaction
mixtures were taken at 75 min and at the end of the reaction. Then
most of the solvent was removed under reduced pressure to give
the residue mixtures 2 and 3 (each about 0.5 mL). CDCl3 was added
to the residue mixtures, and 119Sn NMR spectra were obtained at
room temperature.
Equimolar amounts of DBTO (0.6 mmol) and 1 were heated un-
der reflux in 30 mL of dry MeOH, and 10-mL aliquots of the clear
reaction solutions were taken at intervals of 30, 55, and 80 min,
respectively (35%, 55% and 90% conversion as determined by TLC
monitoring). The reaction sample for 30 min was analyzed as sam-
ple 5. The reaction solutions for 55 and 80 min were cooled to
room temperature, and transparent needle-like crystals crystal-
lized out. After washing with MeOH and drying overnight under
reduced pressure at 35 °C, products 6 and 7 were obtained. The
1H NMR spectra and ESIMS determination of 6 and 7 were then car-
ried out.
Acknowledgments
This research was supported by the National Natural Science
Foundation of China (No. 20272054) and the Natural Science Foun-
dation of Henan Province (No. 0111030300).
Supplementary data
Supplementary data associated with this article can be found, in
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