Synthesizing, Characterizing and Studying the Biological Activity of Some New Schiff-Bases Derivatives Containing the Monosaccharide Moiety

A new series of α-D-glucose as Schiff bases derivatives is synthesized and characterized with studying their bioactivity. Hydroxyl groups at C (1,2&5,6) sugar moiety are converted into acetal form through a reaction with dry acetone using phosphoric acid and anhydrous zinc chloride as catalysts producing 1,2:5,6-di-Oisopropyledine α-D-glucofuranose(I). The five memberd ring acetal of C(5,6) is hydrolyzed with acetic acid (65%)and a reaction of the new product with sodium periodate is carried on to get an aldehyde moiety which is used to produce a new series of Schiff bases through reacting with different amino compounds such as 4amino antipyrene . The suggested chemical structures of the prepared compounds are confirmed by using UV., FT-IR and 1 H-NMR spectra .Most of the prepared compounds show antibacterial activity.


Introduction:
Many sugar analogs containing nitrogen [1] sulfur [2(a,b,c)] or phosphorus [3]as a ring heteroatom have been prepared because of the wide interest in their chemical and biochemical properties.Heteroatom-in-the-ring sugar analogs of 2-amino-and 2-acetamido-2-deoxyhexo pyranoses, which widely occur as a component of many natural products, have also attracted considerable interest [4].Acylated D-glucofuranose and Dglucopyranose derivatives are prepared and another study of in vitro antimicrobial activities of furanose monosaccharides pluse pyranose monosaccharide acylates has been don as a comparative study.While the (SAR) structure activity relationship study show that the acyl derivatives in six-membered pyranose form are more effective by antimicrobial functionality than that of the corresponding acyl derivatives in five-membered furanose form [5]. Schiff bases are widely used as useful organic compounds.They are used ''as intermediates in organic synthesis, dyes, Open Access pigments, polymer stabilizers, and catalysts" [6,7].Glucosamine "Schiff bases", although known since 1922, have received relatively less attention in the literature.For the compounds that consist of the Schiff's base and glucose sub-units a possibility of tautomeric and anomeric equilibria has to be taken into consideration [8].The study of some glucosamine Schiff bases structures by means of an initio calculations and the anomeric and tautomeric equilibria in a DMSO solution by spectroscopic methods is reported [9].Schiff bases or imines are easily generated by condensate carbonyl groups and primary amines.In carbohydrate chemistry, a large number of imines have been reported, both by reaction of sugar aldehydes with amines and by the reaction of aminosugars with aldehydes [10][11][12][13].Helmoz R. reports the synthesis of a series of Dglucosamine derivatives and evaluated their antimicrobial activity.Some of the investigated compounds have a significant antimicrobial activity against positive and negative germ bacterial strains as the fungal strains, so the sugar moiety is necessary due to final results, to increase the biological activity of these compounds [14].The aim of this work is to synthesize and characterize a new series of Schiff bases and investigate their bioactivity.

Materials and Methods:
All chemicals in this work are from BDH., Fluka, Merk and Aldrich Chemicals Co. and used as received.

"Synthesis of Schiff's Bases Derivatives" (IV ae ) .
A mixture of compound (III) (1.0g ; 5.3 mmole) with appropriate amino compounds (5.3 mmole)in absolute ethanol (20ml) and 3drops of glacial acetic acid is refluxed for 24hrs .The completion of the reaction is followed by T.L.C. (benzene: methanol ; 8:2) and by evaporating the solvent, the residue should be recrystallized with absolute ethanol, and the characteristic physical properties of compounds (IV ae) are shown in Table 1 .The acetal group is stable toward alkaline conditions but is readily hydrolyzed by dilute acids [18], thus it is very useful as a blocking agent , and as used in this work for protecting of hydroxyl groups at C -1, C -2 , C -5 and C -6.
A number of procedures using different acid catalysts are available for the acetonation of D-glucose but, generally, they are time-consuming and require large quantities of reagents.These methods include the use of mineral acids such as sulphuric acid [19] and Lewis acids such as ferric chloride [20] and Zinc chloride as catalyst .The 1,2 : 5,6di -Oisopropylidenα -Dglucofuranose (I) is synthesized by using ZnCl 2 catalyst [15],as shown in scheme (1):
The FT-IR spectrum of (III) give (3442 -3388)cm -1 a broad band for 3(OH) groups shows that some of the prepared aldehyde may exist in the hydrate form [22], as shown below: The band at (2794)cm -1 is due to (C-H) aldehydic, and the band at (1716) cm -1 is due to aldehydic carbonyl group.The H -1 -NMR spectrum (III), shows the signals at: 2.008 (S., 3H, 3OH group).The data from the FT -IR and H -1 -NMR spectra agree with the investigation about hydrate form of compound (III).The electronic (UV-Vis) spectrum displays an intense peak at λ max (DMSO) =302.0 nm; Abs.=2.386(DMSO) related to the (n→π*) and (π → π*) transitions of carbonyl group.The final step in this work attempts to prepare the goal Schiff's bases derivatives (IV a-e ) derived from the prepared aldehydic derivative (III) with appropriate amino compounds in equimolar dissolved in absolute alcohol in the presence of drops of glacial acetic acid [23] .Schiff base (IV a ) can be prepared from the reaction between compound (III) and 4amino antipyrine as shown in scheme (1).The FT -IR spectrum of (IV a ) disblay the bands at (3398)cm -1 for (OH)sugar group; (3064)cm -1 for (C -H) aromatic ring; (2929)cm -1 to aliphatic 4(CH 3 ) groups (2 for sugar moiety and 2 for antipyrine compound); 1737 cm -1 to (C=O) carbonyl group for cyclic acetamide; (1651)cm -1 for (C=N) (azomethane group); (1633)cm -1 for (C=C) vinylic of antipyrine, (1593)cm -1 for the (C=C) aromatic ring; and (758 + 698)cm -1 to (C-H) bending vibration for mono substituted aromatic ring.The H 1 -NMR spectrum of (IV a ) displays the signals at: 1.759 (S., 3H, =C-CH 3, methyl in antipyrine moiety); 2.377 (S., 3H, N -CH 3 , methyl to anti pyrine moiety); [6.691-7.367](multiplet, 5H, protons for benzene ring); and 7.478 (d., 1H, imine or azomethane group).The (UV-Vis) spectrum of (IV a ), shows an intense peak at λ max (DMSO) = 278.0nm; Abs.= 2.023 (DMSO) due to the electronic transition (n→π*) and (π -π*) for azomethane group.Another series of Schiff 's Bases (IV b-e ) can be prepared from the reaction between the synthesis of aldehydic compound (III) with aromatic amines as follows in scheme (1).The goal of the new series of Schiff's bases (IV a-e ) synthesized are listed in Table 2.The FT -IR of these derivatives (IV a-e ) show the disappearance of (C=O) (aldehydic in 1716cm -1 ) for compound (III) and formation the (C=N) at frequencies range between (1683 -1600)cm -1 .These data are shown in Table 3 which display the (n→π*) and (π→π*) electronic transitions of the formed (C=N-) group in azomethane and imine moiety of the formed derivatives.

Table ( 3) The UV -Vis , and FT -IR Data for Compounds (IV b-e )
Other (υ) cm -1 υ(C-H)cm -1 Aromatic υ(C=C)cm - Biological Activity:-Organic compounds that contain heterocyclic moiety can be considered as important classes of compound having a wide range of biological activity.The synthesized derivatives such as (III and IV a-e ) in this work are expected to possess a biological activity since they have an active moiety like Schiff 's base.When we use the antibiotics tested with concentration equal to that of the chemical tested, no inhibition of growth for any microorganism is noted so we have to use a concentration fraction of antibiotics (standard) higher than that of the tested chemicals to ensure inhibition.
In this work, the performance of antibacterial test has been achieved as in the disc diffusion method [24].(III and IV a-e ) derivatives are assayed for their antimicrobial activity in vitro against two of each strain of negative and positive grams bacteria like (Escherichia coli, pseudomonas aeroginosa, staphylococcus aureus, Bacillus subtilis) and fungi like candida.The previous bacteria are activated in nutrient growth medium at 37 o C for 24 hour.All the synthesized compounds (III and IV a-e ) are evaluated for their antimicrobial and anti fungi activities.The activity of compounds is determined by measuring the diameter .H.N. analysis is performed via (Euro vector EA 3000A Elemental Analyzer) in AL-al-Bayt University-Jordan.The 1 HNMR spectra (DMSO) are obtained on (a Brucker -300 MHZ Ultra Shield) with (TMS) as an internal standard in University of AL-al-Bayt-Jordan.Thin Layer Chromatography (TLC) is carried out, and the plates are developed with iodine vapor.The results of biological activity are performed in College of Science -University of Baghdad.[15]:-To an efficiently stirred suspension of anhydrous glucose (30gm ; 0.166 mol.) in acetone (200mL) anhydrous pulverized zinc chloride (24gm ; 0.182 mol.