Ecuadorin, a novel tetranortriterpenoid of Guarea kunthiana : structure elucidation by 2-D NMR spectroscopy

Abstract

Ecuadorin (1), C 29 H 34 O 10 , a novel tetranortriterpenoid, has been isolated from Guareakunthiana (Meliaceae) collected in Ecuador. Its structure has been established by spectroscopic methods, mainly 2-D NMR spectroscopy; the value of the FLOCK pulse sequence in the determination of 2- and 3-bond 13 C– 1 H connectivities is illustrated. Ecuadorin has been reduced to the dihydro and tetrahydro derivatives (2 and 3), and these have provided information regarding the stereochemistry of ecuadorin. Stereochemical arguments have been based on observed vicinal 1 H– 1 H coupling constants and NOE measurements, as well as on biosynthetic hypothesis.