Carbohydrate carbocyclization by a zinc-mediated tandem reaction and ring-closing enyne metathesis.
Methyl 5-deoxy-5-iodo-pentofuranosides are reductively ring-opened and propargylated in a tandem fashion in the presence of zinc. The 1,7-enynes thus obtained are subjected to ring-closing enyne metathesis with catalyst B to produce functionalized 1-vinyl cyclohexenes. By adding BnNH(2) to the tandem reaction, an amino group can be introduced in the 1,7-enyne products. Addition of 2-TMS-ethynylcerium(III) chloride after the reductive ring-opening produces the corresponding 1,6-enynes. Further annulation of the product 1,3-dienes can be achieved through a Diels-Alder reaction with good control of stereochemistry. These procedures constitute efficient methods for rapid carbocyclization and annulation of carbohydrates to produce a variety of functionalized five- and six-membered ring systems.
Poulsen
Carina Storm
CS
Department of Chemistry, Building 201, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Madsen
Robert
R
D002241:Carbohydrates / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods; D003500:Cyclization; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry*
D002241:Carbohydrates; D015032:Zinc