2′-Aminoanalogues of the cruciferous phytoalexins spirobrassinin, 1-methoxyspirobrassinin and 1-methoxyspirobrassinol methyl ether: Synthesis and anticancer properties

A method for the synthesis of new 2′-aminoanalogues of spiroindoline phytoalexins is reported. 2′-Aminonalogues of spirobrassinin, 1-methoxyspirobrassinin and 2,2′-diamino analogues of 1-methoxyspirobrassinol methyl ether were prepared by substitution of the methylsulphanyl group on the dihydrothiazole ring of corresponding phytoalexins. Final products were obtained by heating the phytoalexins with aniline or substituted aniline in the absence of solvent at 120 or 140 °C. By replacement of the SCH 3 moiety of ( S )-(−)- or ( R )-(+)-spirobrassinin, enantiomers of 2′-aminoanalogues of spirobrassinin were also synthesized. Determination of their enantiomeric compositions using HPLC with chiral stationary phase revealed partial enantiomeric enrichment. The occurence of a SIDA effect of our 2′-aminonalogue of spirobrassinin was evaluated by examination of a non-racemic mixture in non-polar C 6 D 6 . Complete enantioresolution and distinct signals for two enantiomers were observed for a number of 1 H and 13 C NMR resonances. New synthesized compounds were supplied for testing the antiproliferative effect on a panel of six human cancer cell lines. 2′-Aminoanalogue with CF 3 functionality exhibited more significant inhibitory effects than natural phytoalexins spirobrassinin.