Carbocyclization of carbohydrates: Diastereoselective synthesis of (+)-gabosine F, (-)-gabosine O, and (+)-4-epi-gabosine O

Exploitation of silica gel/chloramine T mediated intramolecular nitrile oxide-alkene cycloaddition (INOC) of sugar-derived oxlmes to carbocycles furnished the first synthesis of gaboslne F from L-arablnose In 12 steps with 23% overall yield, thereby confirming Its absolute configuration. Similarly, efficient syntheses of gaboslne O and 4-epl-gaboslne O were accomplished from D-mannose In 9 and 11 steps with 41% and 38% overall yields, respectively, involving INOC, regeoselective dehydration, and dlastereoselective hydrogenation as the key steps.