Background: Thiosemicarbazone derivatives containing mono- or disaccharide moieties have remarkable
anti-microorganism and antioxidant activities both in vivo and in vitro, therefore thiosemicarbazone
derivatives containing simultaneously monosaccharide or disaccharide moieties have been synthesized.
The conventional catalysts used in reactions of aldehydes or ketones with amines in general
involve only several typically organic and mineral acids, such acetic acid or hydrochloric acid. The
use of strong acidic catalysts in carbohydrate chemistry often have some disadvantages associated with prolonged reaction
times, harsh and harmful reaction conditions, and sometimes, the difficulty in product separations. This problem needs to
be resolved in synthesis of carbohydrate derivatives because of their susceptibility towards the strong acids. Therefore, we
are especially interested in developing the use of inexpensive, simple and efficient catalysts in the synthesis of thiosemicarbazones
having peracetylated mono- and disaccharide moieties.
Methods: The synthesis of some substituted benzaldehyde N-(hepta-O-acetyl-β-D-lactosyl)thiosemicarbazones using different
acidic and basic catalysts. The synthetic reaction was carried out under conventional and microwave-assisted heating
conditions. The antibacterial activity of these thiosemicarbazones against some typical bacteria screened by using the
MIC evaluation method.
Results: Reaction conditions, including catalysts (piperidine, hydrochloric and acetic acids) and heating methods (such as
conventional and microwave-assisted ones), have been investigated for the synthesis of benzaldehyde N-(hepta-O-acetyl-
β-D-lactosyl)thiosemicarbazones. Based on optimal conditions found in the synthesis of benzaldehyde N-(hepta-O-acetyl-
β-D-lactosyl)thiosemicarbazone, the other substituted thiosemicarbazones were synthesized by condensation reactions of
N-(hepta-O-acetyl-β-D-lactosyl)thiosemicarbazide with corresponding different substituted benzaldehydes. Almost all obtained
thiosemicarbazones exhibited remarkable antibacterial activity against Bacillus subtilis, Staphylococcus aureus,
Enterobacter and Escherichia coli.
Conclusion: The optimal conditions were found for synthesis of thiosemicarbazones having β-lactose moiety under conventional
and microwave-assisted heating conditions. Almost all quantitative yields, simple isolation and purification procedures
of these products made it to become a useful procedure for the synthesis of these compounds. Almost all synthesized
thiosemicarbazones exhibited the remarkable antibacterial activity.