Combining a solution-phase derived library with in-situ cellular bioassay: Prompt screening of amide-forming minilibraries using MTT assay

We constructed a minilibrary using a solution-phase synthesis through coupling of three core amino compounds (5′-amino-5′-deoxy uridine, 5′-amino-2′,5′-di-deoxy arabinosyl uridine, and butan-1-amine) with 30 carboxylic acids via amide bond formation. The simplified structural core compound butan-1-amine was selectively coupled with 9 carboxylic acids as control. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay of the crude mixtures showed that analogues derived from fenbufen, butylfenbufen C15; ethacrynic acid, butyl ethacrynic amide C18; and sphingosines, Sph-1, Sph-2 and U27 had an increased cytotoxicity against MCF-7 cells as well as A549 cells. Structural elucidation with molecular docking suggested that cytotoxicity of these compounds is mainly due to the inhibition of enzymes regulating cellular apoptosis.