Issue 42, 2013

Enantioselective synthesis of encecaline-derived potent antimalarial agents

Abstract

The high antiplasmodial activity of racemic benzylamines rac-1 and rac-2 stimulated the synthesis of pure enantiomers. Ellman's chiral sulfinamides (S)-6 and (R)-6 were used as chiral auxiliaries. Condensation of prochiral ketone 5 with enantiomerically pure sulfinamides (S)-6 and (R)-6 and subsequent NaBH4 reduction provided predominantly unlike configured diastereomers (S,R)-8 and (R,S)-8 (ratio unlike-8 : like-8 = 90 : 10). The same transformation of phenol 4 led to the diastereomeric sulfinamides (S,R)-12 and (S,S)-12 in the ratio 60 : 40. Acid hydrolysis of the diastereomerically pure sulfinamides followed by monobenzylation yielded the enantiomerically pure benzylamines (R)-1, (S)-1, (R)-2 and (S)-2. The enantiomeric purity of the products was proven by chiral HPLC and the absolute configuration by CD-spectroscopy. Generally, benzylamines with (R)-configuration show higher antiplasmodial activity than their corresponding (S)-configured enantiomers. Phenol (R)-2 represents a very potent lead against P. falciparum, with an IC50 value of only 0.026 μM against the NF54 strain. The very high eudismic ratio of 34 indicates the enantioselective interaction of phenol (R)-2 with a particular target protein of P. falciparum.

Graphical abstract: Enantioselective synthesis of encecaline-derived potent antimalarial agents

Supplementary files

Article information

Article type
Paper
Submitted
02 Aug 2013
Accepted
02 Sep 2013
First published
09 Sep 2013

Org. Biomol. Chem., 2013,11, 7342-7349

Enantioselective synthesis of encecaline-derived potent antimalarial agents

D. Harel, D. Schepmann, R. Brun, T. J. Schmidt and B. Wünsch, Org. Biomol. Chem., 2013, 11, 7342 DOI: 10.1039/C3OB41583J

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