Syntheses of 1,2-Unsaturated Cyclic Compounds

3 Syntheses of 3,4-Unsaturated Cyclic Compounds - Compound 30, available in three steps from 5-hydroxymethyl-l,6-anhydro-a-L-a//ro-hexopyranose was converted into ewMevoglucosenone by reaction with copper-quinoline (decarboxylation at C-5), zirconium oxide induced olefination at C-3 (reductive decarboxylation) then deacylation and oxidation. The 5-hydroxymethyl analogue of ent-levogluco-senone was also made from the same starting materials.  

A non-carbohydrate route to both enantiomers of levoglucosenone has also been reported in which the furan derivative 31 was desymmetrized using Sharp-less asymmetric dihydroxylation methodology.  

Full details have appeared (see Vol. 28, p. 178, ref. 32 for a preliminary account) on the synthesis of isocyanates such as 32 (useful for preparing N-containing derivatives) by a thermal rearrangement of the corresponding 4-cyanato-2,3-unsaturated derivative.  

The hydride reductive rearrangement of some methyl 4-0-acetyl-3-deoxy-3-C-nitro-2-enopyranoside derivatives to methyl 3-C-nitro-3-enopyranosides is covered in Chapter 10. 

---