title: Thio and epidithio derivatives of methyl beta-lactoside.
abstract: Treatment of methyl beta-lactoside with triphenylphosphine-carbon tetrabromide in pyridine gave the 3',6'-anhydro-6-bromo-6-deoxy derivative, from which 6-thio derivatives were prepared, and methyl 3',4'-O-isopropylidene-beta-lactoside gave the 6,6'-dibromo-6,6'-dideoxy derivative. A dibromide was prepared also from methyl 4',6'-O-benzylidene-beta-lactoside by bromination with Ph3P-CBr4, acetylation, and then treatment with N-bromosuccinimide. Various 6,6'-dithio derivatives were prepared from the 6,6'-dibromide by nucleophilic substitution reactions. Reaction of the 6,6'-dibromide with thiourea led to the 6,6'-epidithio derivative and, with potassium tricarbonate, the bridged 6,6'-trithiocarbonate was formed. The 6,6'-dibromo derivative underwent selective nucleophilic substitution to give a variety of 6'-bromo-6-thio derivatives. Likewise, with azide, the 6-azide was formed first, followed by the 6,6'-diazide and the product of elimination, the 6-azido-5%-ene. Raney nickel-mediated desulphuration of the various 6,6'-dithio derivatives afforded methyl 6,6'-dideoxy-beta-lactoside and desulphuration of the 6'-bromo-6-thio derivatives could be accomplished without reductive dehalogenation to give methyl 6'-bromo-6,6'-dideoxylactoside.
authors.affiliation: Department of Chemistry, King's College London, Great Britain.
authors.forename: M A
authors.initials: MA
authors.lastname: Ali
authors.forename: L
authors.initials: L
authors.lastname: Hough
authors.forename: A C
authors.initials: AC
authors.lastname: Richardson
mesh_terms: D002240:Carbohydrate Sequence; D008759:Methylglycosides / Q000138:chemical synthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D013865:Thioglycosides / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D008759:Methylglycosides; D013865:Thioglycosides; C034207:methyl lactoside