A novel synthesis of precocenes. Efficient synthesis and regioselectiveO-alkylation of dihydroxy-2,2-dimethyl-4-chromanones

Light-Driven Two-Step Preparation of 4-Chromanone Fused to Estrone Derivatives

A protocol involving the irradiation of some 3-(2-alkenyl)estrone and 3-(2-alkenyl)-17-norestrone derivatives under a nitrogen atmosphere in organic solvents (both hexane and MeOH) followed by base-mediated intramolecular oxa-Michael cyclization reaction was investigated under steady-state conditions. The solvent effect and nature of the acyl group on the preparative photoreaction were studied and the multiplicity of the excited state was also demonstrated. The ortho-regioisomers were obtained in modest to good yields. Intramolecular based-mediate cyclization reaction of these synthons led to the formation of a set of novel substituted 4-chromanone moieties fused to estrone (and 17-norestrone) in good yields. This two-step sequential procedure involving a photochemical/intramolecular thermal cyclization strategy will be useful for the preparation of wide heterocyclic-fused-steroid compounds.

The Synthesis, Fungicidal Activity, and in Silico Study of Alkoxy Analogues of Natural Precocenes I, II, and III

This study aimed to synthesize, characterize, and explore the eco-friendly and antifungal potential of precocenes and their derivatives. The organic synthesis of the mono-O-alkyl-2,2-dimethyl 2H-1-chromene series, including the natural product precocene I, and the di-O-alkyl 2,2-dimethyl-2H-1-chromene series, including the natural 2H-1-chromenes precocenes II and III, was achieved. The synthetic compounds were subjected to spectroscopic analysis, 1HNMR,13CNMR, and mass characterization. The antifungal activity of synthesized precocenes I, II, and III, as well as their synthetic intermediates, was evaluated by the poison food technique. Precocene II (EC50 106.8 µg × mL−1 and 4.94 µg mL−1), and its regioisomers 7a (EC50 97.18 µg × mL−1 and 35.30 µg × mL−1) and 7d (EC50 170.58 × µg mL−1), exhibited strong fungitoxic activity against Aspergillus niger and Rhizoctonia solani. Some of the novel chromenes, 11a and 11b, which had never been evaluated before, yielded stronger fungitoxic effects. Finally, docking simulations for compounds with promising fungitoxic activity were subjected to structure–activity relationship analyses against the polygalactouronases and voltage-dependent anion channels. Conclusively, precocenes and their regioisomers demonstrated promising fungitoxic activity; such compounds can be subjected to minor structural modifications to yield promising and novel fungicides.

Design, synthesis and biological evaluation of novel benzoxaborole derivatives as potent PDE4 inhibitors for topical treatment of atopic dermatitis

In this work, a series of structurally novel benzoxaborole derivatives were designed, synthesized and biologically evaluated as PDE4 inhibitors for battling atopic dermatitis (AD). Among them, the majority exhibited superior PDE4B inhibitory activities to that of the lead compound Crisaborole, an approved PDE4 inhibitor. In particular, 72, the most potent PDE4B inhibitor throughout this series, displayed 136-fold improved enzymatic activity (IC₅₀ = 0.42 nM) as compared to Crisaborole (IC₅₀ = 57.20 nM), along with favorable isoform specificity. In the phorbol ester (PMA)-induced mouse ear oedema model, 72 exerted remarkably greater efficacy than Crisaborole at the same dosage (P < 0.05). Moreover, the ointment of 72 exerted dramatically enhanced therapeutic potency than the ointment of Crisaborole (P < 0.05) in the calcipotriol-induced mouse AD model. In addition to the potent in vitro and in vivo activity, 72 displayed favorable safety in the repeated oral dose toxicity study and did not exhibit phototoxicity. With the above attractive biological performance, 72 is worthy of further functional investigation as a novel anti-AD therapeutic agent.

Facile Synthesis of Heterocycles Having Bacteriocidal Activity Incorporating Oleic Acid Residues

Synthesis of various heterocycles having fatty acid residues is described using ethyl-4-(hexadec-7-enyl)-3-oxobutanoate as starting material by reaction with different reagents. Preliminary antibacterial testing showed that the compounds ethyl-4-(hexadec-7-enyl)-3-oxobutanoate and 3-[octadec-9-ene-1-one]-chromen-2-one are the most promising.

Synthesis and insect antifeedant activity of precocene derivatives with lactone moiety

Starting from precocenes I and II, four of their derivatives with a lactone moiety were obtained. The compounds have been assessed as antifeedants against several diverse insect species including the storage pests the confused flour beetle (Tribolium confusum Duv., larvae and adults), the granary weevil beetle (Sitophilus granarius L., adults), and the khapra beetle (Trogoderma granarium Ev., larvae) and against the herbivorous pest insects Colorado potato beetle (Leptinotarsa decemlineata Say, adults and larvae) and aphids (Myzus persicae Sulz.). Precocenes, especially precocene II, showed a very strong antifeedant effect against all storage pests and aphids. The introduction of a lactone moiety caused a decrease in antifeedant activity against these species. Both precocenes were moderately active against L. decemlineata adults. The best antifeedants to this species were precocene derivatives, especially iodolactones. The introduction of iodine into a molecule had a great effect on the antifeedant activity of those compounds.

Synthesis of Azacridone A

[reaction: see text] The first total synthesis of the only known naturally occurring azaacridone alkaloid (1) has been achieved in 10 steps from phloroglucinol. A variety of ortholithiation reactions are described, and a method for overcoming the originally unfavorable regiochemistry of one of them is provided.

Atom economy. Palladium-catalyzed formation of coumarins by addition of phenols and alkynoates via a net C-H insertion

A strategy to achieve ortho substitution of phenols initiated by an ortho-palladation to create coumarins was examined. Indeed, treatment of alkynoates with electron-rich phenols in the presence of a palladium catalyst and an acid does generate coumarins. The scope of the reaction with respect to the phenol and the alkynoates is defined. With unsymmetrical aromatic substrates, generally good regioselectivity that reflects the HOMO coefficients can be observed. In the course of these studies, numerous important naturally occurring coumarins have been synthesized, including fraxinol methyl ether, ayapin, herniarin, xanthoxyletin, and alloxanthoxyletin. The fact that a Pd(0) is the precatalyst rather than a Pd(+2) species and that an acid that reduces Pd(+2) salts, formic acid, functions better than other carboxylic acids raises doubts about the initial working hypothesis. A novel mechanism involving a palladium phenoxide formed from a hydridopalladium carboxylate and phenol is invoked to rationalize the results.

Inhibition of rat liver microsomal lipid peroxidation elicited by 2,2-dimethylchromenes and chromans containing fluorinated moieties resistant to cytochrome P-450 metabolism

2,2-Dimethylchromenes and chromans containing cytochrome P-450 resistant 2,2,2-trifluoroethoxy aryl substituents were synthesized and their activity as lipid peroxidation inhibitors evaluated and compared with that exhibited by the corresponding non-fluorinated derivatives. Lipid peroxidation was stimulated in rat liver microsomes by addition of Fe-ascorbate or NADPH, and determined with the TBARS (thiobarbituric acid reactive substances) test. In assays using Fe-ascorbate stimulation, only those derivatives with a OH group at C6 (i.e. 6 and 12) elicited good inhibitory activities (IC50 = 6.0 and 5.3 microM, respectively). In respect to the NADPH dependent incubations, inhibitory activity of compound 11 (IC50 = 6.0 microM) was the highest found within the 6,7-dialkoxy derivatives tested. Results on metabolism assays with this compound showed the generation of phenol 12 (i.e. the putative active antioxidant species); on the other hand, no metabolite resulting from dealkylation at C7 was detected, thus confirming the resistance conferred by the CF3CH2O group to the cytochrome P-450 promoted cleavage. Finally, in assays where incubations in the presence of NADPH were prolonged up to three hours, inhibitory activity of the non-fluorinated 6,7-dialkoxychroman 8 remained constant, thus suggesting that a continued release of the species responsible for the inhibitory activity was produced. However, inhibition elicited by the fluorinated analog 11 showed a small decrease during the third hour of incubation. This decrease could be attributed to the slight inhibition of the cytochrome P-450 metabolism exerted by substrates bearing the CF3CH2O substituent, which would decelerate the generation of the active phenol species.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of precocene analogs on the nematode Caenorhabditis remanei (var. Bangaloreiensis). I. Structure/activity relations

Precocenes (PI and PII) and 114 of their analogs (PAs) were synthetized and tested on C. remanei embryos for their precocene-like (P-like) activities resulting in unusual development at sublethal doses. The P-like activity was quantitated by plotting the probit of the percentage of the developmentally affected survivors against the (log) dose to obtain the EC plot and the half effective concentration (EC50). All five PAs (PI, PII, 7-ethoxy-PII, 7-(prop-2-ynyloxy)-PI, and 6-methoxy-7-(prop-2-ynyloxy)-PII) which exert both antiallatal activity in insects and P-like activity in nematodes are 7-alkoxy-substituted 2,2-dimethylchromenes. Both activities can be enhanced by an additional 6-MeO-substitution or by an asymmetric 6,7-dialkoxy-substitution, on condition that R-7 is longer than R-6. There are many more similarities than dissimilarities in the structural requirements needed for antiallatal and P-like activities. All but three nonantiallatal PAs effective in nematodes are 7-prop-2-ynyloxy-subsituted; two are symmetrically 6,7-disubstituted, and one is heterosubstituted (thio-PI). All PAs with antiallatal but without P-like activity are 7-monosubstituted with a relatively long alkoxy group. Certain substitutions favor antiallatal activity and others P-like activity. The severe nematocidal effect of 6,7-methylenedioxy-2,2-dimethylchromene (inert in insects) is not accompanied by P-like activity. The present findings lend some indirect support to the supposition that JH-producing cells and/or JH-dependent function(s) might exist in the nematodes.