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TitleSynthesis of pure stereoisomers of benzo[b]thienyldehydrophenylalanines by Suzuki cross-coupling : preliminary studies of antimicrobial activity
Author(s)Abreu, Ana S.
Ferreira, Paula M. T.
Monteiro, Luís S.
Queiroz, Maria João R. P.
Ferreira, Isabel C. F. R.
Calhelha, Ricardo C.
Estevinho, Letícia M.
KeywordsAmino acids
Suzuki coupling
Issue date2004
Citation"Tetrahedron". 60 (2004) 11821-11828.
Abstract(s)Several benzo[b]thienyldehydrophenylalanines were synthesized from pure stereoisomers of the methyl ester of N-(tert-butoxycarbonyl)-beta-bromodehydrophenylalanine as an extension of our previously reported method for the synthesis of dehydrotryptophan analogues to dehydrophenylalanine derivatives. The latter were obtained in high yields by N-deprotection and bromination of N,N-bis-(tert-butoxycarbonyl)-(Z)-dehydrophenylalanine using TFA and NBS. This was carried out in two steps or in a one pot procedure resulting in different E/Z ratios. These compounds were coupled under Suzuki cross-coupling conditions [Pd(PPh3)4, Na2CO3, DME/H2O] with several boronic benzo[b]thienyl acids in good to high yields maintaining the stereochemistry of the starting materials. The best yields were obtained when the boronic acid was in position 7 of the benzo[b]thiophene and with the E isomer of the brominated dehydrophenylalanine. In some cases it was possible to increase the lower yields by changing the Pd source to PdCl2(PPh)2. A model dipeptide was prepared coupling a benzo[b]thienyldehydrophenylalanine with the methyl ester of alanine. Preliminary antimicrobial studies were performed with both isomers of one of the beta,beta-diaryldehydroalanines obtained. The results show that the compounds are selective and very active (very low MICs) against Gram positive bacteria (B. cereus and B. subtilis) the Z-isomer being more active. The compounds are also active against Candida albicans presenting similar MICs.
AccessOpen access
Appears in Collections:CDQuim - Artigos (Papers)

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