Preparation and Conformational Study of Deformyl-Z- and Deformyl-E-geissoschizine Epimers and Na-Boc Derivatives, and Their Nb-Oxides

Syntheses are reported for deformylgeissoschizine isomers (1 -4) and their N,-Boc derivatives (5 -81, as well as for their Nb-oxides (cis and trans) (9 -13) and (16 -20).Predominant conformations of the compounds were determined by nmr measurements.The ( i )-deformylgeissoschizine skeleton allows the existence of four stereoisomers 11 -4 (5 -811.and eight stereoisomers, [ 9 -16 (17 -2411.can be predicted for the corresponding Nboxides (cis and trans) (biogenetic numbering').The correct determination of the different geissoschizine derivatives and their Nb-oxides is a problem of general Model compounds and their Nb-oxides containing the characteristic elements of geissoschizine analogues can be expected to assist in direct