A FACILE ACCESS TO SUBSTITUTED INDENO[1,7-BC]FURANS

The reaction of 4-oxo-beta-ionone 1 with 2 eq. HCN from NaCN in MeOH l eads in excellent yield stereospecifically to a cis-fused tricyclic ri ng system of the indeno[1,7-bc]furan type 5. Acid catalyzed hydrolysis of the imino group in 5 gives lactone 6a which was used to determine the basic structure of the new indeno[1, 7-bc]furans by X-ray analysis . The new compounds were fully characterized by H-1 and C-13 NMR and t he assignments supported by NOE (6a) and H-1-detected one-bond and mul tiple-bond H-1, C-13-COSY (6a-c).