Total synthesis of bidensyneosides A2 and C:: remarkable protecting group effects in glycosylation

Bidensyneosides are a group of five recently identified polyacetylenic glucosides from Bidens parviflora WILLD, a traditional Chinese medicinal plant that contains rich bioactive natural products. It was shown that bidensyneosides inhibited both histamine release and nitric oxide production. The synthesis of bidensyneoside A2 (2) and C (4) as well as 3-deoxybidensyneoside C (5) are described. These syntheses establish a synthetic entry to the bidensyneosides and confirm the stereochemistry at C3. Furthermore, a remarkable protecting Group effect on orthoester formation was observed during the glycosylation reaction. (C) 2004 Elsevier Ltd. All rights reserved.