title: Systematic study on free radical hydrothiolation of unsaturated monosaccharide derivatives with exo- and endocyclic double bonds.
abstract: Exo- and endocyclic double bonds of glycals and terminal double bonds of enoses were reacted with various thiols by irradiation with UV light in the presence of a cleavable photoinitiator. The photoinduced radical-mediated hydrothiolation reactions showed highly varying overall conversions depending not only on the substitution pattern and electron-density of the double bond but also on the nature and substitution pattern of the thiol partner. Out of the applied thiols thiophenol, producing the highly stabilized thiyl radical, exhibited the lowest reactivity toward each type of alkene. In most cases, the hydrothiolations took place with full regio- and stereoselectivities. Successful addition of 1,2 : 3,4-di-O-isopropylidene-6-thio-α-d-galactopyranose to a 2,3-unsaturated N-acetylneuraminic acid derivative, providing a (3 → 6)-S-linked pseudodisaccharide, demonstrated that the endocyclic double bond of Neu5Ac-2-ene, bearing an electron-withdrawing substituent, shows sufficient reactivity in the photoinduced thiol-ene coupling reaction.
authors.affiliation: Research Group for Carbohydrates, University of Debrecen, PO Box 94, H-4010 Debrecen, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Lázár
authors.forename: Magdolna
authors.initials: M
authors.lastname: Csávás
authors.forename: Ádám
authors.initials: Á
authors.lastname: Hadházi
authors.forename: Mihály
authors.initials: M
authors.lastname: Herczeg
authors.forename: Marietta
authors.initials: M
authors.lastname: Tóth
authors.forename: László
authors.initials: L
authors.lastname: Somsák
authors.forename: Terézia
authors.initials: T
authors.lastname: Barna
authors.forename: Pál
authors.initials: P
authors.lastname: Herczegh
authors.forename: Anikó
authors.initials: A
authors.lastname: Borbás
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D009005:Monosaccharides / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D005609:Free Radicals; D009005:Monosaccharides; D010636:Phenols; D013438:Sulfhydryl Compounds; C042983:thiophenol