General synthesis of unnatural 4-, 5-, 6-, and 7-bromo-d-tryptophans by means of a regioselective indole alkylation

Asymmetric synthesis of Fmoc-threo-HOAsn for the total synthesis of nicrophorusamide A

Fmoc-protected β-hydroxyasparagine is an essential structural motif in organic chemistry, widely present in natural products and clinically important drugs, such as antibiotics. Here, a diastereoselective synthesis of Fmoc-protected HOAsn from a simple Garner's aldehyde has been developed. The Fmoc protected Garner's aldehyde reacted with triphenylmethyl isocyanide and formic acid at 60 °C, affording good yield with excellent diastereoselectivity. The application of the Passerini reaction product Fmoc-protected HOAsn for Fmoc-SPPS towards the synthesis of nicrophorusamide A and its analogues has also been reported, which is conducive to systematic SAR studies.

Asymmetric Synthesis and Biological Evaluation of Both Enantiomers of 5- and 6-Boronotryptophan as Potential Boron Delivery Agents for Boron Neutron Capture Therapy

This research investigates boronated tryptophans as potential boron delivery agents for boron neutron capture therapy (BNCT) of cancer. We synthesized both enantiomers of 5- and 6-boronotryptophans (1a and 1b) using simple and inexpensive methods. Their uptake was assessed in two human cancer cell lines, CAL27 (head and neck cancer) and U87-MG (brain cancer), and compared to l-p-boronophenylalanine (l-BPA) as a reference. To determine whether these tryptophan derivatives are substrates for large amino acid transporter 1, we performed molecular dynamics simulations to explore their transport mechanism. Our findings reveal differences in boron compound accumulation between the cancer cell lines, indicating that tryptophan derivatives could serve as effective boron carriers when the clinically used boron carrier, BPA, is ineffective.

Sex-specific metabolic dysregulation in digestive glands of green mussels following exposure to triazophos

As a ubiquitous environmental pollutant in China, triazophos (TP) is known to have neurotoxicity, oxidative stress, and reproductive toxicity to mussels. To investigate the molecular mechanisms of TP toxicity, metabolic changes in the digestive glands of Perna viridis in different sexes were examined after treated with 35 μg/L TP. Notably, 158 significant different metabolites (SDMs) were detected in TP-treated mussels and more than half of the SDMs were lipids and lipid-like molecules, which suggested that TP disturbed the lipid metabolism of P. viridis. In addition, metabolites associated with neurotoxicity and reproductive disturbance were also detected in female and male mussels. Moreover, a larger number of SDMs were found in male mussels (120 SDMs) than females (99 SDMs), and 60 common metabolites exhibited consistent variation tendency and similar magnitude in both sexes. The metabolic alternations in female and male mussels displayed similar protective mechanisms and also sex-specific responses, male mussels were more sensitive to TP exposure. This research provided new data about the molecular mechanisms of TP toxicity and the gender specific changes in mussels after treated by chemicals.

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

An unusual photoredox-catalyzed radical decarboxylative cyclization cascade reaction of γ,γ-dimethylallyltryptophan (DMAT) derivatives containing unactivated alkene moieties has been developed, providing green and efficient access to various six-, seven-, and eight-membered ring 3,4-fused tricyclic indoles. This type of cyclization, which was hitherto very difficult to comprehend in ergot biosynthesis and to accomplish by more conventional procedures, enables the synthesis of ergot alkaloid precursors. In addition, this work describes a mild, environmentally friendly method to activate, reductively and oxidatively, natural carboxylic acids for decarboxylative C-C bond formation by exploiting the same photocatalyst.

Biomimetic Total Synthesis of Clavicipitic Acid: A DDQ-Mediated Intramolecular Cross-Dehydrogenative Coupling Approach

Clavicipitic acid, a communesin alkaloid precursor, has attracted significant attention due to its unique azepino[5,4,3-cd]indole framework. Herein, we report a novel biomimetic synthesis of clavicipitic acid diastereomers by utilizing a DDQ-mediated cross-dehydrogenative coupling (CDC) reaction. The synthesis involves Suzuki coupling for the prenylation of a 4-bromotryptophan derivative, followed by an intramolecular CDC reaction to construct the azepinoindole core. The trans isomer was obtained as the major product, and the two diastereomers were separable. The CDC reaction conditions, including temperature, solvent, and protecting groups, were investigated, and a plausible mechanism for the observed diastereoselectivity was proposed.

Concise catalytic asymmetric synthesis of (R)-4-amino Uhle's ketone

A practical and asymmetric synthesis of (R)-4-amino-5-oxo-1,3,4,5-tetrahydrobenz[cd]indole, an enantiopure framework shared by most ergot alkaloids, was accomplished. Our method involves a Rh(i)-catalyzed 6-exo-trig intramolecular cyclization of an appropriate 4-pinacolboronic ester d-tryptophan aldehyde followed by the oxidation of the resulting secondary benzylic alcohol with a Cu(i)-ABNO catalyst and final deprotection under acidic conditions. This new procedure offers significant advantages over previous synthetic approaches, including brevity, mild reaction conditions, preservation of chiral integrity, and high overall yield and avoids the use of stoichiometric amounts of strongly basic and pyrophoric organometallic reagents.