Reactivity of 6-imidatopurines with benzylhydrazine

Mycobacterium tuberculosis is a bacterium responsible for thousands of deaths worldwide [1]. Its acquired resistance referred to multi-drug resistance (MDR) is due to the restrictive choice of antibiotics, the prolonged course of therapy, globalization and continuous patient noncompliance [2]. Hence, MDR tuberculosis has led researchers worldwide in the quest to find novel drugs to combat these threatening new strains. In our research group, 6-imidatopurines of general structure 1 (Figure 1) were identified as precursors to generate 6-amidinopurines of general structure 2 (Scheme 1) [3,4]. When reacting compounds of structure 1 with a selected hydrazide a (Scheme 1) in the experimental conditions established by our research group, compounds with structure 2 are promptly obtained. When the same reaction conditions were used with benzylhydrazine to obtain products 2 (Scheme 1) an unexpected new derivative was isolated. The proton NMR spectrum of the new derivative showed the absence of the alkyl moiety. Furthermore, the data was not compatible with the purine nucleus. The HMBC and HMQC data showed that the new compound contained the pyrimidopyrimidine core. All the results will be shown and a possible mechanistic approach will be presented and discussed in order to understand the formation of the new derivative.info:eu-repo/semantics/publishedVersio

General synthetic approach to 2-phenolic adenine derivatives

A simple and general “one pot” procedure for the synthesis of 2,9-diarylpurines with one or multiple hydroxyl groups in the 2- aryl unit is described, from the reaction of 5-amino-4-amidinoimidazoles with phenolic aldehydes.National NMR Network, Fundação para a Ciência e a Tecnologia (FCT). F.C.T. (project nºF-COMP-01-0124-FEDER-022716 (ref. FCT PEst-/QUI/UI0686/2011) FEDER-COMPETE, FCT-Portugal and the PhD grant to C. Correia (SFRH/BD/22270/2005)

Synthesis of novel 6-enaminopurines

Two different approaches have been used for the synthesis of 6-enaminopurines 6 from 5-amino-4-cyanoformimidoyl imidazoles 1. In the first approach imidazoles 1 were reacted with ethoxymethylenemalononitrile or ethoxymethylenecyanoacetate under mild experimental conditions and this led to 9-substituted-6-(1-amino-2,2-dicyanovinyl) purines 6a-f or 9-substituted-6-(1-amino-2-cyano-2-methoxycarbonylvinyl) purines 6g-k. These reactions are postulated to occur through an imidazo-pyrrolidine intermediate 7, which rapidly rearranges to the 6-enaminopurine 6. In the second approach 6-methoxyformimidoyl purines 3, prepared in two efficient steps from 5-amino-4-cyanoformimidoyl imidazoles 1, were reacted with malononitrile and methylcyanoacetate with a mild acid catalysis (ammonium acetate or piperidinium acetate) to give 6-enaminopurines 6a, 6d, 6f, 6g and 6k in very good yields. Only low yields were obtained for the 6-enaminopurine 6j, as competing nucleophilic attack on C-8 of either 3d or 6j causes ring opening with formation of pyrimido-pyrimidines 11 and 10a respectively.Universidade do Minho. Fundação para a Ciência e Tecnologia - PRAXIS/C/QUI/10101/1998

Analytical evaluation of fining treatments for white wines contaminated by Ochratoxin A

Mycotoxins are toxic secondary metabolites produced by certain molds. Ochratoxin A (OTA) is one of the most relevant. Its chemical structure is a dihydro-isocoumarin connected at the 7-carboxy group to a molecule of L--phenylalanine via an amide bond. OTA in wine is a risk to consumer health [1]. According to the Regulation No. 123/2005 of the European Commission, the maximum limit for OTA in wine is 2 µg/kg [2]. Then, it is important to control its occurrence. So, the aim of this work was to know the effect of different fining agents on OTA removal from white wine.This work was funded by FEDER funds through the COMPETE and by national funds through FCT, Ref. FCOMP-01-0124-FEDER-028029 and PTDC/AGR-TEC/3900/2012, respectively. Luís Abrunhosa received support through grant SFRH/BPD/43922/2008 from FC

6-Amidinopurines as convenient precursors to pyrimido[5,4-d]pyrimidines for sar studies on Mycobacterium tuberculosis

Thanks are due to University of Minho and Fundação para a Ciência e Tecnologia for financial support (project nºF-COMP-01-0124-FEDER-022716 (ref. FCT PEst-/QUI/UI0686/2011) FEDER-COMPETE, FCT-Portugal and PhD grant awarded to Ana Bacelar SRFH/BD/24959/2005). The NMR spectrometer (Bruker 400 Avance III) is part of the National NMR Network supported with funds from FCT.nºF-COMP-01-0124-FEDER-02271