Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity

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Abstract

Non-covalent interactions are known to play a key role in biological compounds due to theirstabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings,such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act asmodel systems for natural bio-inorganic compounds [2]. A considerable series (twelve novelcompounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119SnMössbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-raycrystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, inthis latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded,through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding andaromatic interactions involving pyrimidine and phenylrings in both complexes drives their self-assembly. Noncovalentinteractions involving aromatic rings are keyprocesses in both chemical and biological recognition,contributing to overall complex stability and formingrecognition motifs. It is noteworthy that inPh2SnCl2(EtOH)2(dptp)2 π–π stacking interactions betweenpairs of antiparallel triazolopyrimidine rings mimick basepairinteractions physiologically occurring in DNA (Fig.1).Mössbauer spectra suggest for Et2SnCl2(dbtp)2 adistorted octahedral structure, with C-Sn-C bond angleslower than 180°. The estimated angle for Et2SnCl2(dbtp)2is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 ischaracterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure.The compounds were screened for their in vitro antibacterial activity on a group of referencestaphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegativepathogens [4] . We tested the biological activity of all the specimen against a group ofstaphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillinresistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P.aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed goodantibacterial activity with a MIC value of 5 μg mL-1 against S. aureus ATCC29213 and alsoresulted active against methicillin resistant S. epidermidis RP62A.
Lingua originaleEnglish
Numero di pagine0
Stato di pubblicazionePublished - 2011

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