title: Regioselectivity in the glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol.
abstract: The glycosylation of 5-(3-chlorobenzo[b]thien-2-yl)-4H-1,2,4-triazole-3-thiol (1) and its 3-benzylsulfanyl and 3-methylsulfanyl derivatives with different glycosyl halides 2-4 has been studied in presence of base. The S-glycosides 5-7 were obtained in the presence of triethylamine, whereas the respective S,N(4)-bis(glycosyl) derivatives 8-10 were synthesized in the presence of potassium carbonate; the S,N(2)-bis(glycosyl) isomer 11 could also be isolated in the case of the galactosyl analog. Similarly, after protecting 1 as 3-benzyl(methyl)sulfanyl derivatives 12 or 13, the N(4)-glycosyl analogs 14-19 as well as minor amounts of S,N(2)-bis(galactosyl) isomers 20 and 21 were formed. The theoretical calculations using AM1 semiempirical methods agreed with the experimental results. Microwave irradiation (MWI) led to higher yields in much less time than the conventional methods, and no change in regioselectivity has been noticed.
authors.affiliation: Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt. Eelashry60@hotmail.com
authors.forename: El Sayed H
authors.initials: el SH
authors.lastname: El Ashry
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Kassem
authors.forename: Hamida M
authors.initials: HM
authors.lastname: Abdel-Hamid
authors.forename: Farida
authors.initials: F
authors.lastname: Louis
authors.forename: Sherine A N
authors.initials: SA
authors.lastname: Khattab
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Aouad
mesh_terms: D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D014230:Triazoles / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D014230:Triazoles