Structural Features of Diacyldodecaheterocycles with Pseudo-C2-Symmetry: Promising Stereoinductors for Divergent Synthesis of Chiral Alcohols.

Pseudo-C2-symmetric dodecaheterocyclic structures, which possess two acyl/aroyl groups disposed on either a cis- or trans-relative configuration, were prepared from the naturally occurring (-)-(1R)-myrtenal. Addition of Grignard reagents (RMgX) to the diastereoisomeric mixture of these compounds unexpectedly showed that nucleophilic additions to the two prochiral carbonyl centers gave the same stereochemical result in both cis/trans diastereoisomers, making unnecessary the separation of this mixture. Noticeably, both carbonyl groups showed different reactivity because one of them is attached to an acetalic carbon and the other to a thioacetalic carbon. Furthermore, addition of RMgX to the carbonyl attached to the former carbon takes place through the re face, while addition to the second one proceeds through the si face, thus affording the corresponding carbinols in a highly diastereoselective process. This structural feature allowed the sequential hydrolysis of both carbinols, yielding separately (R)- and (S)-1,2-diols after reduction with NaBH4. The mechanism of the asymmetric Grignard addition was explained by density functional theory calculations. This approach contributes to the development of the divergent synthesis of structurally and/or configurationally different chiral molecules.

Antinociceptive activity of the ethanolic extract of Trixis angustifolia DC.

The antinociceptive activity of the ethanolic extract of Trixis angustifolia DC. (EETx) was investigated using the acetic acid-induced writhing and the hot-plate tests in mice. In the acetic acid-induced writhing test, mice treated with EETx (50, 100 and 200 mg/kg, p.o.) exhibited reduced writhing (38%, 67%, and 74%, respectively). In the hot-plate test, the three doses administrated increased the nociceptive response time. The phytochemical analysis of EETx led to the isolation of three known compounds, hygric acid (1), 5,6-Dihydroxy-7,8,4'-trimethoxyflavone (2) and xanthomicrol (3). Compound 1 was identified for the first time in this species. These results demonstrate that T. angustifolia has potential central and peripheral antinociceptive effects and support the ethnomedicinal use of this plant.

Trixis angustifolia hexanic extract displays synergistic antibacterial activity against M. tuberculosis.

A phytochemical and antibacterial study of Trixis angustifolia, a species endemic to Mexico, was performed allowing the isolation of six flavones. The minimal inhibitory concentration (MIC) of the hexanic extract, against Mycobacterium tuberculosis H37Rv was 25 µg/mL. The hexanic extract caused a significant inhibition of intracellular mycobacterial growth at 12.5 µg/mL. The biodirected assay of hexane extract enabled the detection of an active fraction (AF) against M. tuberculosis (MIC = 12.5 µg/mL), and a major flavone 1 (pebrellin) with no antimycobacterial activity (MIC > 200 µg/mL). A subsequent combination antimicrobial assay showed a synergistic antimycobacterial effect of AF in combination with pebrellin; the results of the synergistic activity suggest that the antimycobacterial activity found in T. angustifolia is due to the combined action of diverse metabolites present in the plant.