Enolacetal-forming -Elimination in 6-Aldehyde Derivatives of Pyranosides

Enolacetal-forming /S-Elimination in 6-Aldehyde Derivatives of Pyranosides 

On treatment with methyl sulfoxide activated by sulfur trioxide and triethylamine, various partially acetylated hexopyranosides give 4,5-unsaturated 4-deoxy-6-aldehydo pyranosides by oxidation of the primary hydroxyl group. For instance, 131 gives 133 by way of the aldehyde 132. Chromatographically pure methyl 2,3-di-0-acetyl-4-deoxy-6-aZde- 

Glycosides of this type of sugar have been found in conjugation with diterpenes produced by Oospora virescens (Link) Vallr.  

When the activating group is on the ring, a rapid, enolacetal-forming j8-elimination occurs. This type of reaction was observed for 2.3,4,6-tetra-O-acetyl-a-D-glucopyranose (139) on treatment by the foregoing oxidation procedure. The enol acetate 141 was obtained, by way of 140, in a yield of 81%. The same unsaturated, j8-elimination product (141) may be obtained by oxidative elimination starting from 2,3,4,6-tetra-O-acetyl-a-D-mannopyranose.  

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