The O-acetyl-4-O-methyl-(glucurono)xylans were isolated from E. urograndis by extraction with dimethyl sulfoxide, analysed for monosaccharide composition and structurally characterized by NMR spectroscopy. These xylans contained one 4-O-methyl-glucuronic acid substituent and 5.5 acetyl groups for approximately 10 xylose residues. About 10% of 4-O-methyl-glucuronic acid (MeGlcA) units were branched at O-2. The O-acetyl-4-O-methyl-(glucurono)-xylans were composed of the following (1 → 4)-linked β-D-xylopyranosyl structural elements: unsubstituted (51 mol%), 2-O-acetylated (12 mol%), 3-O-acetylated (20 mol%), 2,3-di-O-acetylated (6 mol%) and [MeGlcA α-(1 → 2)] [3-O-acetylated] (11 mol%). The weight-average molar mass and polydispersity of this xylan were 34.9 kDa and 1.16, respectively, as measured by size-exclusion chromatography.

Com o objetivo de avaliar o potencial agroquímico de uma série de compostos com atividade fungicida, foram preparadas e caracterizadas por análises elementares e espectroscopias no infravermelho e de RMN, três novas bis-gama-lactonas análogas ao avenaciolídeo, onde o grupo octila presente nesse produto natural foi substituído por grupos heptila, hexila e pentila. Os efeitos desses compostos e de seus precursores sintéticos no desenvolvimento micelial e na germinação de conídias de Colletotrichum gloesporioides foram avaliados in vitro. As bis-gama-lactonas análogas ao avenaciolídeo foram ativas, enquanto todos os precursores sintéticos não apresentaram atividade nas condições testadas. Este artigo descreve, ainda, a preparação e caracterização de 15 intermediários sintéticos inéditos.

In a study of the antifungal activity of selected compounds as potentials agrochemicals, we have prepared and characterized by elemental analyses, infrared and NMR spectroscopies three new bis-gamma-lactones analogous to avenaciolide, where the octyl group of this natural product was replaced by heptyl, hexyl and pentyl groups. The effects on the mycelia development and conidia germination of Colletotrichum gloesporioides of these compounds and their synthetic precursors were evaluated in vitro. The title compounds were active in the tested conditions, while all the synthetic precursors were inactive. The preparation and characterization of 15 new synthetic intermediates are also described.