A Facile Synthesis of Thiazole Derivatives bearing Imidazole Moiety, Schiff Bases and their O-Glucosides

Abstract

A unique approach for the synthesis of new thiazole O-glycosides is presented in this work. 2-Amino-4-hydroxy-phenyl-1,3-thiazole-5-carboxaldehyde (3a) was reacted with phenyl glyoxal and benzil to form 4-(4-hydroxy-phenyl)-5-(4-phenyl-1H-imidazol-2-yl)-thiazol-2-amine (4a) and 4-(4-hydroxy-phenyl)-5-(4,5-diphenyl-1H-imidazol-2-yl)-thiazol-2-amine (4b), respectively. A series of substituted Schiff bases of 4a and 4b were synthesized reacting with various aryl aldehyde to form 2-(imino substituted benzal)-4-(4-hydroxy-phenyl)-5-(4-phenyl-1H-imidazol-2-yl)-thiazoles (5a-e) and 2-(imino substituted benzal)-4-(4-hydroxy-phenyl)-5-(4,5-diphenyl-1H-imidazol-2-yl)-thiazoles (5f-j). Glucosylation of compounds (5a-j) have been done by using acetobromoglucose as glucosyl donor to afford 2-(imino substituted benzal)-4-(2,3,4,6-tetra-O-acetyl-p-O-β-D-glucosidoxyphenyl)-5-(4-phenyl- 1H-imidazol-2-yl)-thiazoles (6a-e) and 2-(imino substituted benzal)-4-(2,3,4,6-tetra-O-acetyl-p-O-β- D-glucosidoxyphenyl)-5-(4,5-diphenyl-1H-imidazol-2-yl)-thiazoles (6f-j) further on deacetylation to produce 2-(imino substituted benzal)-4-(p-O-β-D-glucosidoxyphenyl)-5-(4-phenyl-1H-imidazol-2-yl)- thiazoles and 2-(imino substituted benzal)-4-(p-O-β-D-glucosidoxyphenyl)-5-(4,5-diphenyl-1Himidazole- 2-yl)-thiazoles (7f-j). The synthesized compounds were characterized by elemental analyses, FTIR, 1H & 13C NMR and electron mass spectra (EI-MS) techniques and then screened for their in vitro antimicrobial activity.