title: The asymmetric syntheses of methyl D-digitoxoside, L-oleandrose and L-cymarose from methyl sorbate, an achiral precursor.
abstract: The addition of 4 eq of chloral to osmundalactone (4S,5R)-4 gave quantitative formation of the hemiacetal derivative (4S,5R)-8, which was treated with methane sulfonic acid to afford the intramolecular Micheal addition product (+)-(3S,4S,5R)-9 possessing a 3,4-cis-dihydroxy-δ-lactone in 78% overall yield from (4S,5R)-4. The obtained (+)-(3S,4S,5R)-9 was subsequently converted to methyl D-digitoxoside (pyranoside) (12) in 13% overall yield and methyl D-digitoxoside (furanoside) (12) in 20% overall yield. The reaction of benzyl-osmundalactone (4R,5S)-3 and MeOH in the presence of Amberlyst A-26 as a basic catalyst gave 3,4-trans-δ-lactone (-)-(3S,4R,5S)-20 in 28% yield and 3,4-cis-δ-lactone (-)-(3R,4R,5S)-21 in 45% yield. Dibal-H reduction of (-)-(3S,4R,5S)-20 followed by catalytic hydrogenation gave L-oleandrose (6) in 86% overall yield, while Dibal-H reduction of (-)-(3R,4R,5S)-21 followed by catalytic hydrogenation provided L-cymarose (7) in 85% overall yield.
authors.affiliation: School of Pharmaceutical Sciences, International University of Health and Welfare, 2600-1 Kitakanemaru, Ohtawara, Tochigi 324-8501, Japan.
authors.forename: Machiko
authors.initials: M
authors.lastname: Ono
authors.forename: Xi Ying
authors.initials: XY
authors.lastname: Zhao
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kato
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Akita
mesh_terms: D002384:Catalysis; D003837:Deoxy Sugars / Q000138:chemical synthesis*; D004073:Digitoxigenin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D006601:Hexoses / Q000138:chemical synthesis*; D006865:Hydrogenation; D009682:Magnetic Resonance Spectroscopy; D009005:Monosaccharides / Q000138:chemical synthesis*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013055:Spectrophotometry, Infrared
chemical_list: D003837:Deoxy Sugars; D006601:Hexoses; D009005:Monosaccharides; C576785:methyl D-digitoxoside; D004073:Digitoxigenin; C035441:oleandrose; C519255:L-cymarose