Síntesis y estudios estructurales de algunos derivados de perhidroindol

Abstract

The biological activity of a series of alkaloids where perhydroindole is the main structural component is directly related to the geometrical isomerism of the hydrogens bound to the chiral centers. Previously, the synthesis of perhydroindole derivatives was carried out, using indoline as starting material, in one step through the reductive amination of ketones using catalytic hydrogenation as the reducing environment. Also, a series of perhydroindole derivatives has been synthesized by the Paal-Knorr reaction followed by catalytic hydrogenation of the pyrrole ring to obtain the corresponding derivative of perhydroindole. However, this method is limited to derivatives with cis configuration. In most of the mass spectra for the derivatives studied was identified, as base peak, a cation corresponding to the loss of forty-three units (M-43). The proposed fragmentation pattern suggests the abstraction of the hydrogen in position 3a as crucial step for this fragmentation. In this work, a process was developed for a diastereoselective synthesis of trans configuration perhydroindole from nonaromatic precursors. The structural studies of these derivatives were conducted by GC-MS and NMR. In addition, a derivative obtained with a phenyl substituent in position 3a of perhydroindole show evidence for the mechanism proposed above, without showing the presence of the cation M-43.