Synthesen biologisch wichtiger Kohlenhydrate, 34. Darstellung 3-C-Methyl-verzweigter Hex-2-enopyranose-Derivate und Untersuchung zur Umlagerung ihrer Glycosyltrichloracetimidate

Synthesis of lemonose derivatives: methyl 4-amino-3-O,4-N-carbonyl-2,4,6-trideoxy-3-C-methyl-α-l-lyxo-pyranoside and its phenyl thioglycoside

Lemonose is a component of the antibiotic lemonomycin and other antibiotics and natural products. Three routes to the synthesis of the title compound, a protected, desmethyl derivative of lemonose, from l-rhamnose or its glycal, were investigated based on electrophilic cyclization, epoxidation-ring opening, and deoxygenation of an intermediate that was used in the synthesis of the amino sugar callipeltose. The deoxygenation route was successful and it provided the title compound, which was then converted to a phenyl thioglycoside.

Synthesis of methyl alpha-L-vancosaminide

The synthesis of methyl alpha-L-vancosaminide from di-O-acetyl-L-rhamnal is described. The allylic alcohol methyl 2,3,6-trideoxy-3-C-methyl-alpha-L-threo-hex-2-enopyranoside was prepared from the glycal, 1,5-anhydro-1,2,6-trideoxy-3-C-methyl-L-ribo-hex-1-enitol, and converted to its N,N-dimethylisourea derivative. The cis amino alcohol functionality in vancosamine was introduced by the electrophilic cyclization of the isourea, followed by hydrolysis of the resulting oxazoline.