Synthesis and Antimicrobial Studies of Some Bis-Glycosyl Isodithiobiurets

Certain 2-S-tetra-O-benzoyl-D-glucopyranosyl-1-aryl-5-tetra-Oacetyl–β-Dgalactopyranosyl-2, 4isodithiobiurets have been synthesized by the interaction of tetra-O-acetyl-β-D-galactopyranosyl isothiocyante and various Stetra-O-benzoyl-Dglucopyranosyl-1-aryl isothiocarbamides. The newly synthesized compounds were screened for their antimicrobial activities.


Introduction
Aryl/alkyl isothiocarbamides, due to their basic nature are found to interact with isothiocyante to form corresponding isodithiobiurests.Several non-glycosidic isodithiobiurests are known for their anticonvulsant and hypnotic activities 1 , several S-glucosides have been described in the literature to possess antimicrobial activities 2 .Glycopyranosyl isothiocyanates are attractive synthons in organic chemistry due to their availability and their tendency to undergo nucleophilic additions and cycloadditions.Several N-glycosides have been found several applications in industries as carbohydrate based detergents 3 and in medicine as antitumour 4 and antitubercular 5 activities.

Experimental
Melting points are uncorrected.Optical rotations [α] D were measured on a Equip-Tronics digital polarimeter model no.EQ 800 in CHCl 3 at 39 0 C. IR spectra were recorded on a Perkin-Elmer spectrum RXI (4000-450 cm -1 ) FTIR spectrometer. 1 HNMR were obtained on a Bruker DRX-300 (300 MHz FT NMR) NMR spectrometer for a sample in CDCl 3 solution with TMS as an internal reference.The mass spectra were recorded on a Joel -SX 102 FAB Mass spectrometer.

2-S-tetra-O-benzoyl-D-glucopyranosyl-5-tetra-O-acetyl
4 isodithiobiurets (3a -g) were prepared by the condensation of S-tetra-O-benzoyl-Dglucopyranosyl 1-aryl isothiocarbamides (2a-g, 0.005 M) and tetra-O-acetyl-β-Dgalactopyranosyl isothiocyanate (1, 0.005 M) in benzene for 4 h.After the reaction was completed the solvent was distilled off and the sticky residue was triturated with petroleum ether to give the solids.The characterization data of the synthesized products is given in the Table 1.

Antimicrobial activity
All the compounds were screened for their antibacterial activity against pathogenic bacteria such as E. coli, S. aureus, P. vulgaris and P. aregenosa by cup plate agar diffusion method 12,13 , at a concentration 100 µg/mL in DMSO by using the standard Amikacin at the same concentration.All compounds were also screened for their antifungal activity against A. niger and C. albicans by cup plate method at a concentration of 100 µg/mL in DMSO by using the standard Fluconazole at the same concentration.The zone of inhibition was measured in mm and is average of three readings.The readings are shown in Table 2.
From the above observations, it is clear that compounds 3c and 3e are active against E.coli, S. aureus and P. aregenosa as compared to standard, while 3b, 3d, 3f and 3g show low or moderate activity against the bacteria.
In antifungal activity, compounds 3a, 3b and 3e show good activity against C. albicans while other are inactive and compounds 3a, 3b, 3c, 3e and 3f show good activity, while others show low activity against A. niger.