Search Results (3)

Commercial ascorbyl-6-O-esters (AEs) are composed of saturated fatty acids with relatively high melting points, resulting in limited solubility in lipophilic media. Therefore, a lipase-catalysed synthesis and purification method for ascorbyl-6-O-oleate (AO) was proposed in this study. The esterification synthesis (i.e., bonding of oleoyl group to ascorbic acid) rate was 19.7% using acetone as the reaction solvent. The transesterification synthesis (i.e., exchange of acyl group with oleic acid (OA) in ascorbyl-6-O-palmitate (AP)) rate increased to 73.8% (AP:OA = 1:3, molar ratio). The esterification product was purified sequentially by liquid–liquid extraction using ethyl acetate and water, followed by hexane and acetonitrile, resulting in 94.8 area% AO confirmed by HPLC. When acetonitrile was replaced with 90% methanol, AO achieved 97.2 area%. Similarly, the transesterification product showed 94.3 area% AEs (AP:AO = 8.9:91.1) after recrystallisation and liquid–liquid extraction. Finally, all purified AO revealed peaks corresponding to the hydroxyl groups at the C-2 and C-3 carbons (11.10 and 8.41 ppm, ¹H-NMR), whereas OA selectively esterified at the C-6 carbon (¹³C-NMR). FT-IR confirmed the presence of the ester bond (1733 cm⁻¹) and olefin structure (3006 cm⁻¹) of OA, and LC-ESI-MS/MS identified AO peaks at m/z 439.3. DSC analysis showed broad endothermic curves at 23.1–46.7 °C when the purified AO samples were pre-cooled at −25 °C. Full article

The synthesis of indole phytoalexin-like analogs related to alkyl (((1-(4-substitutedphenyl)-3-oxo-3-phenylpropyl)thio)carbonothioyl)-ʟ-tryptophanate 1a–d and the evaluation of their antifungal activity against the phytopathogen Fusarium oxysporum is reported. The target compounds were synthesized in the following two stages: (1) the initial esterification of ʟ-tryptophan, which reacted with trimethyl silane chloride and simple aliphatic alcohols (R = Me, Et) under microwave irradiation (MWI) at 100 °C to obtain the respective alkyl ester 2a–b; (2) the resulting mixture of ʟ-tryptophanates 2a–b with carbon disulfide and (E)-chalcone 3a–b under MWI at 50 °C during 60 min, followed by purification through classical column chromatography (55–76% yields). The products were obtained as mixtures of (S,R) and (S,S) diastereoisomers. An LC-DAD-MS analysis allowed us to establish the ratio of these diastereoisomers, and subsequent DFT/B3LYP-based computational calculations of the NMR ¹H chemical shifts suggested that the major diastereoisomer involved an (S,R) absolute configuration, comprising more than 60% of the mixture. The compounds 1a–d were subjected to an antifungal activity test against the phytopathogen F. oxysporum using an amended medium-based assay. Compound series 1 showed inhibition percentages of 80% at the first concentration and IC₅₀ values between 0.33 and 5.71 mM, demonstrating greater potential as antifungal agents compared to other ʟ-tryptophan derivatives like alkyl (2S)-3-(1H-indol-3-yl)-2-{[(1Z)-3-oxobut-1-en-1-yl]amino}propanoate, which presented lower inhibition percentages. In summary, phytoalexin analogs derived from ʟ-tryptophan and (E)-chalcones significantly inhibited the mycelial growth of Fusarium oxysporum, indicating their potential as effective antifungal agents. Full article

The potassium salt of E- and Z-2,3-diphenylpropenoic acids prepared in situ could be esterified efficiently in DMSO with the appropriate alkyl halides at room temperature. In this way 10 previously undescribed esters of these acids were synthesised and characterised. Excellent yields were observed for most of the E isomers and the more hindered Z esters were also obtained in good yields, far better than those obtained applying the classical acid-catalysed esterification reaction. Full article