Synthetic studies concerning the crinine alkaloid haemultine

The racemic form, (±)-1, of the structure originally assigned to the crinine alkaloid haemultine has been prepared for the first time. A key step involved the conversion of compound (±)-4 into the isomeric cis-C3a-arylhexahydroindole (±)-3 using a Pd0-catalysed intramolecular Alder-ene reaction. The amino-alcohol (±)-2 derived from the latter compound reacted with paraformaldehyde in the presence of trifluoroacetic acid to give, via a Pictet-Spengler reaction, the target (±)-1. The diastereoisomeric Mosher esters 15 and 16 obtained by coupling the racemate (±)-1 with the R-form, 14, of the Mosher acid could be separated chromatographically and then reductively cleaved to give the enantiomerically pure compounds (+)-1 and (-)-1, respectively. The physical and spectroscopic data derived from the former enantiomer are consistent with the proposition that the title natural product is, in fact, a mixture of (+)-1 and its Δ2,3-double bond isomer. Journal compilation