On–Off Mechano-responsive Switching of ESIPT Luminescence in Polymorphic <i>N</i>‑Salicylidene-4-amino-2-methylbenzotriazole

We report the synthesis of a luminescent <i>N</i>-salicylidene aniline derivative, <i>N</i>-salicylidene-4-amino-2-methylbenzotriazole (<b>1</b>), and the study of its polymorphism and photophysical properties. Three phases showing yellow (<b>1-Y</b>), orange (<b>1-O</b>), and red (<b>1-R</b>) fluorescence have been isolated and characterized by thermal and single crystal X-ray analysis. The photoluminescence results from excited-state intramolecular proton transfer process and the quantum yield is strongly dependent on polymorphism (Φ_1‑Y = 0.87, Φ_1‑O = 0.11, Φ_1‑R = 0.028). The poorly emitting <b>1-R</b> can be easily prepared, converted to the bright <b>1-Y</b> by grinding, and reverted to <b>1-R</b> through melting and annealing, giving rise to a luminescence on–off mechano-responsive cycle. The different photophysical properties are explained with the variable π-overlap and molecular conformation changes in the three polymorphs, characterized by a very similar crystal packing. By DFT calculations, the absorption properties were explained as dependent on the torsion angle between the two planar portions of the molecule, which affects the equilibrium between enol and keto forms in the ground state

Lentisone, a New Phytotoxic Anthraquinone Produced by Ascochyta lentis, the Causal Agent of Ascochyta Blight in Lens culinaris

An aggressive isolate of Ascochyta lentis obtained from lentil (Lens culinaris L.) produced various metabolites in vitro. The metabolites were isolated from the culture filtrates and characterized by spectroscopic, chemical, and optical methods. A new phytotoxic anthraquinone, named lentisone, was isolated and characterized as (1<i>S*</i>,2<i>S*</i>,3<i>S*</i>)-1,2,3,8-tetrahydroxy-1,2,3,4-tetrahydro-6-methylanthraquinone together with the well-known pachybasin (1-hydroxy-3-methylanthraquinone), tyrosol, and pseurotin A. Lentisone, tyrosol, and pseurotin A were phytotoxic to lentil, with lentisone the most toxic of all. The toxicity of these compounds is light-dependent. Finally, lentisone was also found to be phytotoxic to chickpea, pea, and faba bean, with toxicity in the latter higher than in any other tested legume, including lentil

Phomentrioloxin: A Phytotoxic Pentasubstituted Geranylcyclohexentriol Produced by <i>Phomopsis</i> sp., a Potential Mycoherbicide for <i>Carthamus lanatus</i> Biocontrol

A new phytotoxic geranylcyclohexenetriol, named phomentrioloxin, was isolated from the liquid culture of <i>Phomopsis</i> sp., a fungal pathogen proposed for the biological control of <i>Carthamus lanatus</i>, a widespread and troublesome thistle weed belonging to the Asteraceae family causing severe crop and pastures losses in Australia. The structure of phomentrioloxin was established by spectroscopic, X-ray, and chemical methods as (1<i>S</i>,2<i>S</i>,3<i>S</i>,4<i>S</i>)-3-methoxy-6-(7-methyl-3-methylene-oct-6-en-1-ynyl)­cyclohex-5-ene-1,2,4-triol. At a concentration of 6.85 mM, the toxin causes the appearance of necrotic spots when applied to leaves of both host and nonhost plants. It also causes growth and chlorophyll content reduction of fronds of <i>Lemna minor</i> and inhibition of tomato rootlet elongation. Finally, in preliminary bioassays, phomentrioloxin did not show any antibacterial, fungicidal, or zootoxic activities

Phomentrioloxin: A Phytotoxic Pentasubstituted Geranylcyclohexentriol Produced by <i>Phomopsis</i> sp., a Potential Mycoherbicide for <i>Carthamus lanatus</i> Biocontrol

A new phytotoxic geranylcyclohexenetriol, named phomentrioloxin, was isolated from the liquid culture of <i>Phomopsis</i> sp., a fungal pathogen proposed for the biological control of <i>Carthamus lanatus</i>, a widespread and troublesome thistle weed belonging to the Asteraceae family causing severe crop and pastures losses in Australia. The structure of phomentrioloxin was established by spectroscopic, X-ray, and chemical methods as (1<i>S</i>,2<i>S</i>,3<i>S</i>,4<i>S</i>)-3-methoxy-6-(7-methyl-3-methylene-oct-6-en-1-ynyl)­cyclohex-5-ene-1,2,4-triol. At a concentration of 6.85 mM, the toxin causes the appearance of necrotic spots when applied to leaves of both host and nonhost plants. It also causes growth and chlorophyll content reduction of fronds of <i>Lemna minor</i> and inhibition of tomato rootlet elongation. Finally, in preliminary bioassays, phomentrioloxin did not show any antibacterial, fungicidal, or zootoxic activities

Higginsianins A and B, Two Diterpenoid α‑Pyrones Produced by <i>Colletotrichum higginsianum</i>, with <i>in Vitro</i> Cytostatic Activity

Two new diterpenoid α-pyrones, named higginsianins A (<b>1</b>) and B (<b>2</b>), were isolated from the mycelium of the fungus <i>Colletotrichum higginsianum</i> grown in liquid culture. They were characterized as 3-[5a,9b-dimethyl-7-methylene-2-(2-methylpropenyl)­dodecahydro­naphtho­[2,1-<i>b</i>]­furan-6-ylmethyl]-4-hydroxy-5,6-dimethylpyran-2-one and 4-hydroxy-3-[6-hydroxy-5,8a-dimethyl-2-methylene-5-(4-methylpent-3-enyl)­decahydro­naphthalen-1-ylmethyl]-5,6-dimethylpyran-2-one, respectively, by using NMR, HRESIMS, and chemical methods. The structure and relative configuration of higginsianin A (<b>1</b>) were confirmed by X-ray diffractometric analysis, while its absolute configuration was assigned by electronic circular dichroism (ECD) experiments and calculations using a solid-state ECD/TDDFT method. The relative and absolute configuration of higginsianin B (<b>2</b>), which did not afford crystals suitable for X-ray analysis, were determined by NMR analysis and by ECD in comparison with higginsianin A. <b>1</b> and <b>2</b> were the C-8 epimers of subglutinol A and diterpenoid BR-050, respectively. The evaluation of <b>1</b> and <b>2</b> for antiproliferative activity against a panel of six cancer cell lines revealed that the IC₅₀ values, obtained with cells reported to be sensitive to pro-apoptotic stimuli, are by more than 1 order of magnitude lower than their apoptosis-resistant counterparts (1 vs >80 μM). Finally, three hemisynthetic derivatives of <b>1</b> were prepared and evaluated for antiproliferative activity. Two of these possessed IC₅₀ values and differential sensitivity profiles similar to those of <b>1</b>

Higginsianins A and B, Two Diterpenoid α‑Pyrones Produced by <i>Colletotrichum higginsianum</i>, with <i>in Vitro</i> Cytostatic Activity

Two new diterpenoid α-pyrones, named higginsianins A (<b>1</b>) and B (<b>2</b>), were isolated from the mycelium of the fungus <i>Colletotrichum higginsianum</i> grown in liquid culture. They were characterized as 3-[5a,9b-dimethyl-7-methylene-2-(2-methylpropenyl)­dodecahydro­naphtho­[2,1-<i>b</i>]­furan-6-ylmethyl]-4-hydroxy-5,6-dimethylpyran-2-one and 4-hydroxy-3-[6-hydroxy-5,8a-dimethyl-2-methylene-5-(4-methylpent-3-enyl)­decahydro­naphthalen-1-ylmethyl]-5,6-dimethylpyran-2-one, respectively, by using NMR, HRESIMS, and chemical methods. The structure and relative configuration of higginsianin A (<b>1</b>) were confirmed by X-ray diffractometric analysis, while its absolute configuration was assigned by electronic circular dichroism (ECD) experiments and calculations using a solid-state ECD/TDDFT method. The relative and absolute configuration of higginsianin B (<b>2</b>), which did not afford crystals suitable for X-ray analysis, were determined by NMR analysis and by ECD in comparison with higginsianin A. <b>1</b> and <b>2</b> were the C-8 epimers of subglutinol A and diterpenoid BR-050, respectively. The evaluation of <b>1</b> and <b>2</b> for antiproliferative activity against a panel of six cancer cell lines revealed that the IC₅₀ values, obtained with cells reported to be sensitive to pro-apoptotic stimuli, are by more than 1 order of magnitude lower than their apoptosis-resistant counterparts (1 vs >80 μM). Finally, three hemisynthetic derivatives of <b>1</b> were prepared and evaluated for antiproliferative activity. Two of these possessed IC₅₀ values and differential sensitivity profiles similar to those of <b>1</b>