Tetrahedron Letters最新文献

A simple and efficient metal-free strategy has been developed for the synthesis of 1,5-disubstituted pyrazole derivatives by using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) medium and ultrasound irradiation. The condensation reactions of β-enaminone and aromatic hydrazine have taken place at room temperature with the assistance of sonication. The protocol provides rapid access to various N-aryl substituted pyrazole compounds with excellent functional group tolerance and yields. Notably, the eco-friendly and cost-effective method allows the conversion within a short time and under mild conditions.

Achieving the synthesis of densely-functionalized, cage-like alkaloids has long proven quite challenging, with the success of individual events often being acutely sensitive to minute differences in the geometry and strain of the substrate, particularly as each successive ring is constructed. As such, consideration of what ring to form last has proven to be of particular design significance. In this review, we analyze seminal examples where the E-ring of various structurally related caged indole alkaloids has been targeted as the site of terminal ring closure. As these examples demonstrate, a terminating E-ring approach can enable highly efficient syntheses, but often bespoke solutions are required, given the near-consistent failure of conventional cyclization strategies to forge such rings.

In this work two known monoacyl glycerols, glycerol 1-monopalmitate and glycerol 1-monostearate, were isolated for the first time from B. mycoides, B. weihenstephanensis and B. toyonensis. These monoacyl glycerol compounds showed good antifungal activity specially, against Lasiodiplodia theobromae, which is the fungus affecting cacao. A study of the cell damage done by these monoacyl glycerols was performed in three phytopathogens, resulting in severe damage of reproductive structures, indicating for the first time the potent antifungal activity of these compounds. It could be a promising result to apply in agriculture crops. This work contributes with the research about Bacillus species secreting metabolites, since this is the first time that is reported about the mono acyl glycerols as compounds secreted by Bacillus species. Furthermore, this work explores the role that Bacillus genus can play in controlling important fungi in agriculturally important crops such as cacao.

In this paper, M-TzDha-COF composed of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (Tz) and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (Dha) was synthesized by grafting carboxyl groups onto COF framework via the solvent-free esterification. M-TzDha-COF retains the porous structure and has good crystallinity and high thermal stability. M-TzDha-COF exhibits selective adsorption and efficient removal of methylene blue dye with the maximum adsorption capacity of 95 mg·g⁻¹. M-TzDha-COF can adsorb methylene blue rapidly and maintain high adsorption efficiency after several cyclic applications. The adsorption of methylene blue on M-TzDha-COF is consistent with the pseudo-second-order adsorption kinetic model and Langmuir adsorption model. Adsorption is caused by three interactions: π-π stacking between the triazine group and methylene blue, electrostatic interaction between the carboxyl group and the methylene blue cationic portion, and hydrogen bonding interaction. Fast kinetics, high adsorption capacity and good reusability make carboxyl functionalized COF have great potential in removing methylene blue dye from water.

An investigation on the aqueous ethanol extract of the powdered twigs of Aphania oligophylla has afforded a skeletal new sesquiterpenoid aphanoid A (1) and one new aromadendrane-type sesquiterpenoid aphanoid B (2), as well as six known sesquiterpenoids (3–8). Their structures including the absolute configurations were characterized based on spectroscopic data analysis and X-ray crystallography. Compound 1 featuring an unprecedented tricyclo[6.3.1.0^3,5]dodecane scaffold, is likely rearranged from the bicyclogermacrene-type sesquiterpenoid. Among those compounds, 2 at 10 μL showed moderate antimalarial effect.

An efficient and concise method is hereby reported for the synthesis of pyrido[3,4-c]pyridazin-8(7H)-ones from the commercially available material, methyl 4,6-dichloropyridazine-3-carboxylate. The four-step reaction process involves Suzuki coupling, Buchwald coupling, ammoniation, and intramolecular cyclization. The advantage of this route represents the development of a novel C5 site-selective Suzuki monocoupling of 3,5-dichloropyridazine, with an overall yield of over 73 %.

3‑Amino oxindole Schiff base has been used as an efficient substrate company with p‑quinone methides for a new highly diastereoselective and enantioselective 1,6-conjugate addition in the presence of a O-allyl-N-(9-anthracenylmethyl) cinchonidinium bromide phase transfer catalyst under mild reaction conditions. A broad series of chiral quaternary 3-amino oxindoles with 4-hydroxybenzyl scaffold were smoothly obtained in good to excellent yields with excellent diastereoselectivities (>20:1) and enantioselectivities (up to 99 % ee). A typical scale-up preparation and subsequent hydrolysis of a pyridine substrate was successfully performed and a potential valuable chiral amino-pyridine bifunctional chiral building block was obtained, which is structurally feasible as chiral ligand for asymmetric metallic catalysis.

Alkylphosphorus compounds have been widely used in ligands, flame retardants, bioorganic and medical chemistry, agrochemicals, chelating agents, and organic synthesis. However, traditional methods for C(sp³)P bond construction are somewhat unsatisfactory. In recent years, a number of outstanding phosphorylation reactions have been achieved, which might open vast opportunities for the synthesis of alkylphosphonates. This digest review covers the recent advances in C(sp³)P cross-coupling reactions using readily available P(O)H compounds and phosphites as phosphorus sources since 2020, and the corresponding reactions are categorized into two types according to alkyl substrates bearing C(sp³)H bonds or C(sp³)LG (LG = leaving group) bonds.

This review explores the coinage metal-catalyzed or-mediated oxidative heteroarylation of activated arenes or arenes possessing DG and focuses on the role of directing groups in influencing the efficiency and selectivity of product conversions. This leads to the construction of new CC and CN bonds. The synthesized heteroaryl products by this method are part of the many natural products, and have significance in pharmaceuticals, agrochemicals, and advanced material chemistry.

In this paper we reported a new range of amphiphilic Janus dendrimers, which consist of sodium carboxylate and chlorambucil molecules as the peripheral groups, as novel potential anticancer dendritic drug delivery agents. The dendrons and structural features of the Janus dendrimers were analyzed by different techniques (¹H, ¹³C one- and two-dimension NMR spectroscopy, FTIR, UV–vis and mass spectrometry). The amphiphilic dendrimers were loaded with the water-insoluble anticancer drug, chlorambucil, by a covalent bond. The hydrophilic group, sodium carboxylate, was obtained from the Behera’s amine moieties. The Janus dendrimers take advantage of a dendritic display to carry different amounts of chlorambucil molecules. The Janus dendrimers chlorambucil-sodium-carboxylate as terminal groups were more active than its tert-butyl and OH substituted analogues against cancer cells. These results provide an effective entry to the development of new drug nanocarriers.