ORMOSIA ALKALOIDS: IV. STEREOCHEMISTRY OF ORMOJANINE; STRUCTURE AND STEREOCHEMISTRY OF PIPTANTHINE, DASYCARPINE, AND ORMOSININE

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Abstract
By using the known structure and stereochemistry of the alkaloid ormosanine, C20H35N3 (I), as reference, the structure and stereochemistry of the isomeric compounds piptanthine (II), tetrahydro-ormojanine (XIV), isotetrahydro-ormojanine (XIII), and dasycarpine (XX) have been elucidated by isomerization and reduction experiments. Three additional C20H35N3 bases possessing the ormosanine skeleton have been prepared by the reduction of pyridine VII. Thus, of the 15 possible stereoisomers of ormosanine, 7 are now known.The study leads to the stereo-formula XIX for the alkaloid ormojanine, C20H31N3. The alkaloid ormosinine has been found to be a dimer of panamine.Stereochemical aspects of the catalytic and chemical reductions of the double bonds and pyridine rings contained in the described compounds are discussed. A possible biogenetic intermediate is proposed which explains the presence of both antipodal series of Ormosia alkaloids in nature.