4,6‐Ditosyl‐2‐desoxy‐α‐methyl‐D‐allosid. Desoxy‐zucker, 28. Mitteilung

Abstract

Bei der Reduktion von 4,6‐Ditosyl‐2,3‐anhydro‐α‐methyl‐D‐allosid mit Lithiumaluminiumhydrid reagieren die 3 funktionellen Gruppen in der Reihenfolge Anhydroring > prim. Tosylgruppe > sek. Tosylgruppe. Je nach den gewählten Bedingungen lassen sich so Derivate der 2‐Desoxy‐D‐allose, der Digitoxose oder der Cymarose bereiten.

Mechanisms Of Epoxide Reactions

“…Certain sugar epoxides may be conformationally stable, even though they contain no 4,6-O-benzylidene group or 1 ,6-anhydro ring. Thus methyl 2,3-anhydro-4,6-ditosyl-a-~-alloside probably exists almost entirely in that conformation in which the bulky tosyloxy groups are equatorial and, if this is so, the attack of lithium aluminum hydride a t Cz (22,23) is another example of diaxial opening: H Anhydrides of monocyclic pyranoses, whose conformations are not stabilized, will normally exist as an equilibrium mixture of two conformations, corresponding to the two half-chair conformations of a six-membered ring. Hence, even if ring opening is always diaxial, two products are possible, as shown in figure 6 for 2,3-anhydrides, and each of these products can exist in either or both of two conformations.…”