Browsing by Author "Xavier, N. M."
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- Synthesis and biological evaluation of sugars containing α,β-Unsaturated γ-LactonesPublication . Xavier, N. M.; Silva, S.; Madeira, P. J. A; Florêncio, M. H.; Silva, Filipa; Justino, Jorge; Thiem, J.; Rauter, A. P.The stereocontrolled synthesis of new sugar derivatives carrying the α,β-unsaturated δ-lactone (butenolide) moiety is described. Sugar-fused or sugar-linked butenolides can be constructed by an efficient reaction sequence involving Wittig olefination of 3- or 5-keto sugars and intramolecular cyclization of the intermediate γ-hydroxy α,β-unsaturated esters. The antimicrobial activities of the products and that of a known sugar-derived pyranoid α,β-unsaturated δ-lactone were investigated against six pathogenic bacteria and six fungi. The pyranoid α,β-unsaturated δ-lactone 29 proved to be the most active compound in this series towards the plant pathogenic fungi Colletotrichum coffeanum (coffee berry disease) and Pyricularia oryzae (rice blast disease).
- Synthesis of sugars embodying conjugated carbonyl systems and related triazole derivatives from carboxymethyl glycoside lactones: evaluation of their antimicrobial activity and toxicityPublication . Xavier, N. M.; Goulart, Margarida; Neves, Ana Maria; Justino, Jorge; Chambert, S.; Rauter, A. P.; Queneau, Y.The synthesis of a series of pyranoid derivatives comprising a conjugated carbonyl function and related triazole derivatives, structurally suitable for bioactivity evaluation, was achieved in few steps starting from readily available carboxymethyl glycoside lactones (CMGL). 3-Enopyranosid-2-uloses were generated by oxidation/elimination of tri-O-acylated 2-hydroxy pyranosides. Subsequent Wittig olefination provided stereoselectively 2-C-branched-chain conjugated dienepyranosides with (E)-configuration around the exocyclic double bond. A heterogeneous CuI/Amberlyst-catalyzed 'click' chemistry protocol was used to convert glycosides bearing a propargyl moiety into the corresponding 1,2,3-triazoles. These new molecules were screened for their in vitro antibacterial and antifungal activities and those containing conjugated carbonyl systems demonstrated the best efficacy. (N-Dodecylcarbamoyl)methyl enone glycerosides were the most active ones among the enones tested. The alpha-anomer displayed very strong activities against Bacillus cereus and Bacillus subtilis and strong activity toward Enterococcus faecalis and the fungal pathogen Penicillium aurantiogriseum. The corresponding beta-anomer presented a very strong inhibitory effect against two fungal species (Aspergillus niger and P. aurantiogriseum). (N-Dodecyl-/N-propargyl/or N-benzylcarbamoyl) methyl dienepyranosides exhibited selectively a strong activity toward E. faecalis. Further acute toxicity evaluation indicated low toxic effect of the (N-dodecylcarbamoyl)methyl enone glyceroside alpha-anomer and of the carbamoylmethyl dienepyranosides N-protected with propargyl or benzyl groups