Synthesis and Characterization of New Schiff Bases Heterocyclic Compounds and Their N-Acyl, Thiourea and Imidazole Derived from D-Erythroascorbic Acid

The new Schiff bases derived from D-erythroascorbic acid containing heterocyclic unit were synthesized by condensation of D-erythroascorbic acid with aromatic amine (containing 1,3,4-oxadiazole or 1,3,4-thiadiazole unit) in dry benzene using glacial acetic acid as a catalyst. D-erythroascorbic acid[IV] was synthesized by four steps (Scheme 1), while the primary aromatic amine which is containing 1,3,4-oxadiazole[VII] or 1,3,4-thiadiazole[XII] synthesized by the reaction of 4-methoxybenzoyle- hydrazine[VI] with 4-aminobenzoic acid or by the reaction tuloic acid with thiosemicarbazide, respectively in the presence of POCl3. The new imidazole derivatives were synthesized by three-steps reactions starting with corresponding Schiff bases[VIII ] or[XIII ]. N-acyl compounds[IX]a,b and[XIV]a,b were synthesized by addition reaction of acid chloride to imine group of Schiff bases in dry benzene. The second step include reaction of thiourea with N-acyl derivatives in Na2CO3 medium to yield N-thiourea compounds[X]a,b and[XV]a,b. The third step involves cyclization reaction of N-thiourea derivatives with benzoin in DMF to result new imidazole derivatives[XI]a,b and[XVI]a,b. The structure of the synthesized compounds have been characterized by their melting points, elemental analysis and by their spectral data; FTIR, UV-Vis, mass, 1HNMR, and 13CNMR spectroscopy. All the synthesized compounds have been screened for their antibacterial activities. They exhibited good antibacterial activity against Escherichia coli (G-) and Staphylococus aureus (G+).