(S)-2-Tryptoline-3-carboxylic acid methyl ester

(R)-ricinoleic acid methyl ester obtained from commercial castor oil was transformed in a three-step procedure into its S-enantiomer in overall 36% yield using ionic liquid (1-butyl-3-methylimidazolium acetate) in the key step process. The developed procedure provides easy access to (S)-ricinoleic acid and its methyl ester of over 95% enantiomeric excess. Optical rotations of the newly obtained compounds as well as their chromatographic and spectral characteristics are provided and discussed in the context of enantiopurity both of the substrate material and the final products.

We report herein the synthesis of 4-amino-2,8-dichloropyrido[3,2-d]pyrimidine derivatives 2 and their regioselective diversification through S(N)Ar and metal-catalyzed cross-coupling reactions. While amination of 2 took place selectively at C-2, the regioselectivity of thiol or thiolate addition depended on the reaction conditions. Selective C-8 addition was obtained in DMF with Hünig's base and C-2 addition in (i)PrOH. These C-2 or C-8 regioselective thiolations provided an opportunistic way to selectively activate either of the two positions toward the metal-catalyzed cross-coupling reaction. The chloride could be efficiently substituted by Suzuki-Miyaura reaction and the sulfanyl group by Liebeskind-Srogl cross-coupling reaction, demonstrating the orthogonality of both reactive centers. The development of regioselective conditions for these different transformations yielded the synthesis of 4-amino-2,6,8-trisubstituted pyrido[3,2-d]pyrimidine derivatives, with various substituents.

Treatment with plant elicitors can be a promising method to induce Pinus pinaster tolerance against the pinewood nematode (PWN), Bursaphelenchus xylophilus, by promoting plant antioxidant system, micronutrient accumulation and by modulating plant-associated bacterial populations. To test this hypothesis, plants were sprayed with methyl jasmonate (MeJA), salicylic acid (SA) or benzo (1,2,3)-thiadiazole-7-carbothioic acid-S-methyl ester (BTH), and evaluated until 35 days after-inoculation (dai) for: i) extent of foliar symptoms; ii) nematode density inside stem tissues; iii) proxies for oxidative damage and antioxidant activity, iv) micronutrient concentration and v) bacterial diversity. Compared with non-elicited plants, plant elicitation, particularly with BTH, significantly decreased nematodes density inside stem tissues (by 0.63-fold). Concordantly, without elicitation plant mortality reached 12.5% while no mortality was observed in elicited plants. BTH-elicited plants had significantly higher concentrations of anthocyanins and carotenoids at the end of the assay than SA-elicited and MeJA-elicited plants, which possibly contributed to the lower PWN colonization and degree of foliar symptoms observed. Accordingly, MeJA and SA led to increased lipid peroxidation at 28 dai (by 2.64- and 2.52-fold, respectively) in comparison with BTH (by 1.10-fold), corroborating its higher potential in increasing plant antioxidative response during infection. Moreover, carotenoids showed a negative correlation with nematode migration, whereas polyphenols showed a positive correlation. Elicitors also induced changes in the bacterial community of infected P. pinaster plants, increasing the diversity of specific populations. Finally, elicitors induced significant changes in micronutrients accumulation in plant tissues, namely a decrease in the concentration of B, Mn and Ni in plants treated with BTH compared to those treated with the other elicitors. Altogether, results suggest that elicitation with MeJA, SA and, particularly, BTH, increases tolerance against B. xylophilus by promoting plant antioxidant system, changing the accumulation of essential micronutrients and modulating plant-associated bacterial diversity.