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The phytopathogenic fungus Botrytis cinerea, which causes gray mold disease, has become a limiting factor on agricultural production. B. cinerea field control is made mainly using chemical fungicides, which has led to the spreading of resistant populations of this fungus. Thus, the quest of new fungicides molecules has been focused on synthesis of natural product-inspired compounds. The main aim of this work is to synthesize prenylated phenol derivatives and to assess their potential application as antifungal agents with minimal phytotoxic effects. Thus, new prenylphenols (4, 5, and 7) have been obtained by microwave irradiation with yields ranging from 2.4% to 42.9%, whereas compounds 8 and 9 were synthesized with yields of 25.6% and 54.1%, respectively. The effect of different concentrations of these compounds on B. cinerea spore germination, and their phytotoxic effect on tomato (Solanum lycopersicum L.) seed germination and root growth, were evaluated. Obtained results indicate that biological activities of all tested compounds are concentration-dependent. Interestingly, compound 7 exhibits the highest antifungal activity against B. cinerea spores (IC50 < 50 µg/mL) with minimal phytotoxicity on tomato seed germination and root growth. In contrast, compounds 2 and 3 are active against spores (IC50 = 461 and 325 µg/mL, respectively) but, at the same time, their phytotoxicity is important at the highest concentrations. These results indicated that the presence of hydroxyl and methyl substituents on the aromatic ring of these compounds induces variations in biological activities, and compound 7 could be a promising candidate as a sporicidal agent.

The reactions of phenol (or ortho -allylphenol) with paraformaldehyde and substituted anilines (or allylamine) yielded 3-allyl-, 3-aryl- or 8-allyl-3-aryl-1,3-benzoxazines. A study of the corrosion inhibitory activity of the synthesized compounds revealed that the degree of protection ( Z ) in the case of 8-allyl homologues in a 15% HCl solution reaches 96–98%. The absence of an allyl substituent at the C 8 carbon atom of the benzoxazine core leads to a decrease in protection to 75–76%.

Background (Hydroxy)cinnamyl alcohols and allylphenols, including coniferyl alcohol and eugenol, are naturally occurring aromatic compounds widely utilised in pharmaceuticals, flavours, and fragrances. Traditionally, the heterologous biosynthesis of (hydroxy)cinnamyl alcohols from (hydroxy)cinnamic acids involved CoA-dependent activation of the substrate. However, a recently explored alternative pathway involving carboxylic acid reductase (CAR) has proven efficient in generating the (hydroxy)cinnamyl aldehyde intermediate without the need for CoA activation. In this study, we investigated the application of the CAR pathway for whole-cell bioconversion of a range of (hydroxy)cinnamic acids into their corresponding (hydroxy)cinnamyl alcohols. Furthermore, we sought to extend the pathway to enable the production of a variety of allylphenols and allylbenzene. Results By screening the activity of several heterologously expressed enzymes in crude cell lysates, we identified the combination of Segniliparus rugosus CAR (SrCAR) and Medicago sativa cinnamyl alcohol dehydrogenase (MsCAD2) as the most efficient enzymatic cascade for the two-step reduction of ferulic acid to coniferyl alcohol. To optimise the whole-cell bioconversion in Escherichia coli , we implemented a combinatorial approach to balance the gene expression levels of SrCAR and MsCAD2. This optimisation resulted in a coniferyl alcohol yield of almost 100%. Furthermore, we extended the pathway by incorporating coniferyl alcohol acyltransferase and eugenol synthase, which allowed for the production of eugenol with a titre of up to 1.61 mM (264 mg/L) from 3 mM ferulic acid. This improvement in titre surpasses previous achievements in the field employing a CoA-dependent coniferyl alcohol biosynthesis pathway. Our study not only demonstrated the successful utilisation of the CAR pathway for the biosynthesis of diverse (hydroxy)cinnamyl alcohols, such as p -coumaryl alcohol, caffeyl alcohol, cinnamyl alcohol, and sinapyl alcohol, from their corresponding (hydroxy)cinnamic acid precursors but also extended the pathway to produce allylphenols, including chavicol, hydroxychavicol, and methoxyeugenol. Notably, the microbial production of methoxyeugenol from sinapic acid represents a novel achievement. Conclusion The combination of SrCAR and MsCAD2 enzymes offers an efficient enzymatic cascade for the production of a wide array of (hydroxy)cinnamyl alcohols and, ultimately, allylphenols from their respective (hydroxy)cinnamic acids. This expands the range of value-added molecules that can be generated using microbial cell factories and creates new possibilities for applications in industries such as pharmaceuticals, flavours, and fragrances. These findings underscore the versatility of the CAR pathway, emphasising its potential in various biotechnological applications.

The two-dimensional cyclic potential energy surfaces for internal rotation of the allyl substituent and its vinyl fragment in o-allylphenol (o-APh) depending on the OH group orientation relative to the allyl substituent were constructed by a B3LYP/6-31G method. It is shown that o-APh exists in the gas phase as a mixture of eight non-planar rotamers (A, B, C, D, E, F, G, and H) and their eight optical isomers (A1, B1, C1, D1, E1, F1, G1, and H1). An intramolecular H-bond (IHB) O–H...π occurs only in four rotamers (A, B, A1, and B1). The content of such rotamers in the gas phase is 47.2% (as calculated by the B3LYP/cc-pVTZ method). Taking into account the solvation effect in the polarizable continuum model (PCM) for a solution of o-APh in cyclohexane decreases the total content of rotamers with an IHB (A and B) to 37.7%. The ratio of rotamers with OH groups bonded by an IHB and with free OH groups that is predicted theoretically agrees with the value measured experimentally from IR spectra of o-APH in CCl4 solution.