title: Sugar-derived 2-S-substituted-2H-pyran-3(6H)-ones: synthesis and reactivity.
abstract: A practical procedure for the preparation of chiral 2-S-substituted-2H-pyran-3(6H)-ones is described. According to the reaction conditions, 1,5-anhydro-2,3,4-tri-O-acetyl-D-threo-pent-1-enitol (1) reacted with thiophenol under Lewis acid catalysis to afford the polysubstitution product 1,5-anhydro-2,3,4-tri-S-phenyl-2,3,4-trithio-D,L-threo-pent-1-enitol (2) or phenyl 2,4-di-O-acetyl-3-deoxy-1-thio-alpha- and beta-D-glycero-pent-2-enopyranoside (3 and 4, respectively). The iodine-promoted addition of thiophenol or alpha-toluenethiol to 1 gave (2S)-2-phenylthio-2H-pyran-3(6H)-one (5) or its 2-benzylthio analogue 6, but these products showed low enantiomeric excesses (ee approximately 40-60%). However, dihydropyranone 5 with high optical purity (ee>94%) was successfully obtained by treatment of 4 with iodine in acetonitrile. On the other hand, it was established that the benzylthio group of 5 exerts high stereocontrol in reduction and cycloaddition reactions performed on the alpha,beta-unsaturated carbonyl system.
authors: CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Argentina.
authors: Christian A Iriarte
authors: CA
authors: Capaccio
authors: Oscar
authors: O
authors: Varela
mesh_terms: D010429:Pentoses / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D011714:Pyrans / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D010429:Pentoses; D010636:Phenols; D011714:Pyrans; D013438:Sulfhydryl Compounds; C042983:thiophenol