Organic & Biomolecular Chemistry最新文献

[16]Thiatriphyrin(2.2.1)s containing one thiophene and two pyrroles connected via five meso-carbons were synthesized by condensing a new precursor, meso-fused thiatripyrrane, with an appropriate aryl aldehyde in CH₂Cl₂ under acid-catalyzed inert conditions followed by open air oxidation with DDQ. These are the first examples in a new series of stable triphyrin(2.2.1)s and both experimental and theoretical studies indicated the nonaromatic nature of the macrocycles. The macrocycles showed strong absorptions in the UV-visible region and exhibited easier oxidations and difficult reductions. The protonated derivatives generated by the addition of TFA to the macrocycles in CHCl₃ showed distinct colour changes with significant bathochromic shifts in absorption bands. DFT optimized structures of one of the [16]thiatriphyrins and its protonated derivative revealed that the thiophene ring was almost perpendicular whereas the two pyrrole rings were almost in plane with the mean plane defined by the five meso-carbons and TD-DFT studies were in agreement with the experimental observations.

A practical transition metal-free approach for the selective benzylation of NH-sulfoximines has been disclosed by using simple elemental iodine as the catalyst and tert-butyl hydroperoxide (TBHP) as the terminal oxidant. Comparing with known methods for the construction of N-benzylated sulfoximines, our protocol shows broad substrate scope with respect to both diarylmethanes and alkylarenes, and can be conducted in air with good functional group tolerance.

The [3 + 2] cycloaddition of dicyanoepoxides with benzylidene Meldrum's acid under microwave irradiation and solvent-free conditions was explored for the synthesis of trioxaspirodecanes. This method presents a highly diastereo- and regioselective route to spiro cycloadducts, delivering similar stereoselectivity to conventional reflux in toluene but with shorter reaction times and improved yields.

We have devised a copper-catalysed tandem annulation reaction to generate a new class of bicyclic nucleoside analogues (BCNAs), namely, amino-substituted thiazolopyrimidine ribonucleosides. The reaction between triacetyl-5-iodo-cytidine and an appropriate organic isothiocyanate in the presence of a Cu salt and ligand resulted in the formation of an amino-substituted thiazolopyrimidine moiety. This reaction was found to be compatible with a range of aliphatic and aromatic isothiocyanates, affording the corresponding products in moderate to good yields. The methodology was extended to diacetyl-2'-deoxy-5-iodo-cytidine and we could also establish the applicability of the methodology on a gram scale. Finally, acetyl deprotection of amino-substituted thiazolopyrimidine ribonucleosides was achieved by treatment with NH₃ in MeOH.

2-Arylbenzoxazinone undergoes direct ortho-C-H thiolation by using diaryl disulfide in the presence of a Ru(II)-phosphine catalytic system and an Ag additive. The protocol has been generalized with benzoxazinone substrates having different substituents and a series of disulfides. ortho-Selenylation has also been performed successfully using diphenyl diselenide under similar catalytic conditions. Based on control experiments and reported literature studies, a probable mechanistic pathway has been suggested.

Correction for ‘Total syntheses of Kavaratamide A and 5-epi-Kavaratamide A’ by Tieshun Ren et al., Org. Biomol. Chem., 2025, https://doi.org/10.1039/d4ob01409j.

Herein, we report a cascade annulation of readily available isocyanobiaryls with simple aldehydes via photoredox catalysis, providing a straightforward approach towards valuable 6-hydroxyalkylated phenanthridines. Mechanistic studies indicated the generation of a key acyl radical from aldehydes by hydrogen atom abstraction with a bromine radical. This protocol exhibits exceptional chemoselectivity, excellent tolerance of various functional groups and mild reaction conditions. Its synthetic utility was demonstrated by a gram-scale reaction and various facile manipulations of the free hydroxyl group to furnish diverse phenanthridine derivatives.

In this study, we explored the chemical modification of toll-like receptor 9 (TLR9) agonist DNA using a highly fluorescent thymine analogue, ThexT, focusing on its structural and photophysical characteristics. ThexT-labelled CpG oligonucleotides effectively demonstrated intracellular localisation within macrophage cell lines. Notably, immunostimulatory activity varied depending on the site of ThexT incorporation within the TLR9 agonist sequence. The introduction of fluorescent nucleobases offers a useful approach for visualising immunostimulatory oligonucleotides and for modulating immune responses.

We present a visible-light-promoted radical cascade cyclization reaction via sulfonylmethylation, cyano insertion, and radical cyclization of unactivated alkenes bearing cyano groups. This strategy enables the rapid synthesis of sulfonylmethylated phenanthridines under mild conditions with broad substrate compatibility, operational simplicity, and mild reaction conditions. The developed approach provides a novel pathway for assembling complex polycyclic nitrogen-containing frameworks, addressing a critical synthetic challenge and expanding the toolbox of photochemical transformations in organic synthesis.

The labile tautomerism of N-unsubstituted 5-acyl-4-pyridones, which exist in the form of 4-pyridone or 4-hydroxypyridine depending on the solvent, has been demonstrated. This equilibrium determines the reactivity of pyridones and their ability to undergo substitution reactions of the OH group. A regioselective and convenient method for the construction of functionalized pyrazolo[4,3-c]pyridines (30-93%) based on the intramolecular amination reaction of 4-pyridones with hydrazines has been developed. The heterocyclization of N-alkyl-4-pyridones is accompanied by a dealkylation reaction. The reaction with hydroxylamine as a nucleophile can be used for the construction of the isoxazolo[4,5-c]pyridine core. Methods have been developed for further modification of the 5-azaindazole fragment via alkylation and decarboxylation. The antiproliferative properties of the prepared 5-azaindazoles were studied in relation to cancer (Hep-2, MCF) and normal cell lines (FH and Vero), and the compounds demonstrated relevant biological activity for further design of new molecules for antitumor therapy.