STRATEGIES FOR THE SYNTHESIS OF ENANTIOMERICALLY PURE MEDIUM-SIZED CARBOCYCLES FROM CARBOHYDRATES.

A series of strategies (the Pauson-Khand reaction and the 1,3-dipolar cycloaddition reaction) have been analyzed in order to develop new and original synthetic protocols for the synthesis of enantiomerically pure medium-sized carbocycles. The intramolecular Pauson-Khand reaction on dideoxy-3,4:5,6-bis-O-(1-methylethylidene)-D/L-glycero-D-gluco-non-1-en-8 -ynitol (4) is a low yielding, but highly stereoselective acyclic enyne precursor 1,2-procedure for the synthesis of bicyclo[5.3.0]decanones of type 5. In the second approach ("the nitrone route"), the intramolecular nitrone cycloaddition of precursors 14 and 19 derived from D-mannose has afforded the corresponding 9-oxa-8-azabicyclo[5.3.0]decanes as a mixture of trans fused isomers, in a critically dependent reaction of a pre-existing isopropylidene group which entropically favors the approach of the reactive species; this is the first documented example of a 1,3-dipolar cycloaddition in 7-alkenyl nitrones. [ABSTRACT FROM AUTHOR]