Heteroyohimbane a noyau furannique. Nouvelle voie d'acces aux derives de la furo[3,2-c]pyrone et de la furo[3,2-c]pyridine

3,4-Dicarbomethoxyfuran bearing an acetonyl or a phenacy group in the 2 position w3as prepared by pyrolysis of the dihydrocyclo adduct from methyl acetylendicarboxylate and 2-acetonyl- or 2-phenacylfuran. Condensation of 2-acetonyl-3,4-dicarbomethoxyfuran with tryptamine gave a new heteroyohimbane with a furan ring, indolo2,3-a]furo3,2-c]quinolizine, a potential precursor of yohimbane. Ketodiacids from saponification allow one to obtain derivatives of the following heterocyclic ring systems, namely 4H-furo3,2-c]pyran-4-one and furo3,2-c]pyridine.