Inhibition of cobalamin-dependent methionine synthase by substituted benzo-fused heterocycles

Direct C-H Alkylation of Benzothiadiazoles via Organic Photoredox Catalysis

2,1,3-Benzothiadiazole is widely used as a privileged scaffold in pharmaceuticals and organic functional materials. Nonetheless, many current methods for the functionalization of 2,1,3-benzothiadiazole rely on preactivation, transition metal catalysts/promoters, or an elevated reaction temperature. Herein we disclose a transition-metal-free visible-light-induced photocatalytic method for the direct C-H alkylation of 2,1,3-benzothiadiazole using readily accessible carboxylic acid derivatives, i.e., N-hydroxyphthalimide esters (NHPEs), as alkylating reagents under room temperature. This mild and scalable method is highlighted by the late-stage installation of the benzothiadiazole scaffold in drugs and natural products.

Metal-Free, Rapid, and Highly Chemoselective Reduction of Aromatic Nitro Compounds at Room Temperature

In this study, we developed a metal-free and highly chemoselective method for the reduction of aromatic nitro compounds. This reduction was performed using tetrahydroxydiboron [B₂(OH)₄] as the reductant and 4,4'-bipyridine as the organocatalyst and could be completed within 5 min at room temperature. Under optimal conditions, nitroarenes with sensitive functional groups, such as vinyl, ethynyl, carbonyl, and halogen, were converted into the corresponding anilines with excellent selectivity while avoiding the undesirable reduction of the sensitive functional groups.

Methionine synthase supports tumour tetrahydrofolate pools

Mammalian cells require activated folates to generate nucleotides for growth and division. The most abundant circulating folate species is 5-methyl tetrahydrofolate (5-methyl-THF), which is used to synthesize methionine from homocysteine via the cobalamin-dependent enzyme methionine synthase (MTR). Cobalamin deficiency traps folates as 5-methyl-THF. Here, we show using isotope tracing that MTR is only a minor source of methionine in cell culture, tissues or xenografted tumours. Instead, MTR is required for cells to avoid folate trapping and assimilate 5-methyl-THF into other folate species. Under conditions of physiological extracellular folates, genetic MTR knockout in tumour cells leads to folate trapping, purine synthesis stalling, nucleotide depletion and impaired growth in cell culture and as xenografts. These defects are rescued by free folate but not one-carbon unit supplementation. Thus, MTR plays a crucial role in liberating THF for use in one-carbon metabolism.

Design, synthesis and biological activity of N5-substituted tetrahydropteroate analogs as non-classical antifolates against cobalamin-dependent methionine synthase and potential anticancer agents

Cobalamin-dependent methionine synthase (MetH) is involved in the process of tumor cell growth and survival. In this study, a novel series of N⁵-electrophilic substituted tetrahydropteroate analogs without glutamate residue were designed as non-classical antifolates and evaluated for their inhibitory activities against MetH. In addition, the cytotoxicity of target compounds was evaluated in human tumor cell lines. With N⁵-chloracetyl as the optimum group, further structure research on the benzene substituent and on the 2,4-diamino group was also performed. Compound 6c, with IC₅₀ value of 12.1 μM against MetH and 0.16-6.12 μM against five cancer cells, acted as competitive inhibitor of MetH. Flow cytometry studies indicated that compound 6c arrested HL-60 cells in the G₁-phase and then inducted late apoptosis. The molecular docking further explained the structure-activity relationship.

Metabolite Profiling: A Tool for the Biochemical Characterisation of Mycobacterium sp

Over the last decades, the prevalence of drug-resistance in Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, has increased. These findings have rekindled interest in elucidating the unique adaptive molecular and biochemistry physiology of Mycobacterium. The use of metabolite profiling independently or in combination with other levels of "-omic" analyses has proven an effective approach to elucidate key physiological/biochemical mechanisms associated with Mtb throughout infection. The following review discusses the use of metabolite profiling in the study of tuberculosis, future approaches, and the technical and logistical limitations of the methodology.

Past, present, and future of nitrous oxide

INTRODUCTION

For a drug that has been omnipresent for nearly 200 years, nitrous oxide's (N2O) future seems less certain than its illustrious past. Environmental concerns are coming to the fore and may yet outweigh important clinical benefits.

SOURCES OF DATA

After determining the scope of the review, the authors used PubMed with select phrases encompassing the words in the scope. Both preclinical and clinical reports were considered.

AREAS OF AGREEMENT

The analgesic and anaesthetic advantages of N2O remain despite a plethora of newer agents.

AREAS OF CONTROVERSY

N2O greenhouse gas effect and its inhibition of key enzymes involved in protein and DNA synthesis have provided further fuel for those intent on eliminating its further clinical use.

GROWING POINTS

The use of N2O for treatment-resistant depression has gained traction.

AREAS TIMELY FOR DEVELOPING RESEARCH

Comparative studies for N2O role in combatting the prescription opioid analgesic epidemic may well provide further clinical impetus.

Design, synthesis, and enzyme kinetics of novel benzimidazole and quinoxaline derivatives as methionine synthase inhibitors

Methionine synthase catalyzes the transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine, producing methionine and tetrahydrofolate. Benzimidazole and deazatetrahydrofolates derivatives have been shown to inhibit methionine synthase by competing with the substrate 5-methyltetrahydrofolate. In this study, a novel series of substituted benzimidazoles and quinoxalines were designed and assessed for inhibitory activity against purified rat liver methionine synthase using a radiometric enzyme assay. Compounds 3g, 3j, and 5c showed the highest activity against methionine synthase (IC₅₀: 20 μM, 18 μM, 9 μM, respectively). Kinetic analysis of these compounds using Lineweaver-Burk plots revealed characteristics of mixed inhibition for 3g and 5c; and uncompetitive inhibition for 3j. Docking study into a homology model of the rat methionine synthase gave insights into the molecular determinants of the activity of this class of compounds. The identification of these drug-like inhibitors could lead the design of the next generation modulators of methionine synthase.

13C and 15N NMR spectra of aminobenzimidazoles in solution and in the solid state

The (13)C [hexadeutero-dimethylsulfoxide (DMSO-d(6)), hexamethyl-phosphoramide (HMPA)-d(18)and solid-state] and (15)N (solid-state) NMR spectra of six C-aminobenzimidazoles have been recorded. The tautomerism of 4(7)-aminobenzimidazoles and 5(6)-aminobenzimidazoles has been determined and compared with B3LYP/6-311 + + G(d,p) calculations confirming the clear predominance of the 4-amino tautomer and the slight preference for the 6-amino tautomer. GIAO-calculated absolute shieldings compare well with experimental chemical shifts.