1,6‐Anhydrofuranosen, XI. 1,6‐Anhydro‐α‐L‐idofuranose

Abstract

Die Titelverbindung 13 wird aus geeigneten benzylierten Derivaten mit gluco-Konfiguration auf verschiedenen Wegen synthetisiert. Bei der Darstellung wird die Moglichkeit der selektiven Hydrogenolyse von axialen Benzylgruppen in 5-Stellung in diesen Verbindungen genutzt, die eine anschlieknde Konfigurationsurnkehr durch eine Oxidations-, Reduktionssequenz erlaubt und somit von der D-g/UCO-in die L-ido-Reihe filhrt. 13 ist in den sich in saurer Losung der Idose einstellenden Gleichgewichtsgemischen lediglich zu 0.08% enthalten. Es wird anhand der CC-Methyltalose gezeigt, dal3 der 1 ,(j-Anhydrofuranose-Anteil in diesen Gleichgewichten beim Wechsel der 4 H ydroxygruppe von einer sekundaren xu einer tcrtiaren erheblich steigt. l,&Anhydrofuranoses, XI I). -1,GAnhydro-a-L-idofuranoseThe title compound 13 is prepared on different routes from suitable benzyl derivatives with glucoconfiguration. Prcparations use the susceptibility of axial 5-0-benzyl groups in this compounds to selective hydrogenolysis, thus allowing subsequent inversion of configuration in this position from D -~~U C O to I -id0 by an oxidation/reduction sequence. Only 0.08% of 13 are found in the equilibrium mixture of idose in acidic medium. It is shown with 4-C-rnethylialose as example, that the amount of l,&anhydrofuranoses in these cquilibria rises significantly by changing the hydroxy groups in Cposition from secondary to tertiary ones. 1,6Anhydrohexofuranosen sind ebenso wie die entsprechenden Pyranoside innere Glycoside (,,Glycosane") und erlauben nicht nur eine Chemie unter Verzicht auf bestimmte Schutzgruppen, sondern ermoglichen aufgrund des ihnen zugrundeliegenden bicyclischen Systems hoch regio-und stereoselektiv verlaufende Reaktionen. Daruberhinaus stellen sie relativ starre Molekule dar, die fur die Konformationsanalyse von be-Liebigs Ann. Chem. 1982, 613-625

Water‐soluble organic compounds in biomass burning aerosols over Amazonia 1. Characterization by NMR and GC‐MS

“…Duplicate analyses showed that the precision of the determination is typically 20%. Samples of the commercially unavailable compounds, arabinosan (1,5-anhydro-␣-D-arabinofuranose), xylosan (1,5-anhydro-␤-D-xylofuranose), 1,6anhydro-␤-D-glucofuranose, and N-acetyl-2-aminoglocosan (1,6-anhydro-2-acetamido-2-deoxyglucose) were synthesized according to published procedures [Köll et al, 1973[Köll et al, , 1982[Köll et al, , 1990[Köll et al, , 1991. Authentic standards of all the other compounds were obtained from Sigma Chemical Company.…”

Carbasugar analogues of galactofuranosides: β-O-linked derivatives and towards β-S-linked derivatives

“…[36][37][38] Addition of vinylmagnesium bromide to the hemiacetal 2 in THF gave a mixture (6:1) of epimers 3a and 3b, separable by column chromatography, in 87% yield (Scheme 2). When vinylmagnesium chloride in THF was used instead, the stereoselectivity improved to ca.…”

Convergent and Stereoselective Synthesis of Iminosugar-Containing Galf and UDP-Galf Mimicks: Evaluation as Inhibitors of UDP-Gal Mutase

“…Under the conditions reported by Kobayashi (Z-NH 2 , TMSOTf), the corresponding N -Z glycosylamine was obtained as a single product in 85% yield using 2 equiv of benzyl carbamate. When only 1.5 equiv or less of the carbamate was used, 2 was obtained as a mixture (from 96/4 to 84/16) with the byproduct 2 ‘ (1,6-anhydro-2,3,5-tri- O -benzyl-β- d -glucofuranose) arising from a Lewis acid-assisted regioselective de- O -benzylation at O-6 (Scheme ). It is noteworthy that the reaction also works directly from 2,3,5,6-tetra- O -benzyl- d -glucofuranose.…”