Amination-modified lignin recovery of aqueous phosphate for use as binary slow-release fertilizer.

To address the global phosphorus crisis and solve the problem of eutrophication in water bodies, the recovery of phosphate from wastewater for use as a slow-release fertilizer and to improve the slow-release performance of fertilizers is considered an effective way. In this study, amine-modified lignin (AL) was prepared from industrial alkali lignin (L) for phosphate recovery from water bodies, and then the recovered phosphorus-rich aminated lignin (AL-P) was used as a slow-release N and P fertilizer. Batch adsorption experiments showed that the adsorption process was consistent with the Pseudo-second-order kinetics and Langmuir model. In addition, ion competition and actual aqueous adsorption experiments showed that AL had good adsorption selectivity and removal capacity. The adsorption mechanism included electrostatic adsorption, ionic ligand exchange and cross-linked addition reaction. In the aqueous release experiments, the rate of nitrogen release was constant and the release of phosphorus followed a Fickian diffusion mechanism. Soil column leaching experiments showed that the release of N and P from AL-P in soil followed the Fickian diffusion mechanism. Therefore, AL recovery of aqueous phosphate for use as a binary slow-release fertilizer has great potential to improve the environment of water bodies, enhance nutrient utilization and address the global phosphorus crisis.

Highly Enantioselective Synthesis of N-Unprotected Unnatural α-Amino Acid Derivatives by Ruthenium-Catalyzed Direct Asymmetric Reductive Amination.

An unprecedented highly enantioselective Ru-catalyzed direct asymmetric reductive amination of α-keto amides with ammonium salts has been disclosed, efficiently offering valuable enantioenriched N-unprotected unnatural α-amino acid derivatives bearing a broad range of aryl or alkyl α-substituents. This protocol features easily accessible substrates, good functional-group tolerance and excellent enantiocontrol, making it a good complementary approach to the known methods. Moreover, this method is also applicable to the preparation of N-unprotected unnatural α-amino acid derivatives containing an additional stereogenic center at the ß-position through a dynamic kinetic resolution (DKR) process. Convenient transformations of the obtained products into chiral N-unprotected unnatural α-amino acids, drug intermediates, peptides, and organocatalysts/ligands further showcase the utility of this method.

Effect of Phosphorus Precursor, Reduction Temperature, and Support on the Catalytic Properties of Nickel Phosphide Catalysts in Continuous-Flow Reductive Amination of Ethyl Levulinate.

Levulinic acid and its esters (e.g., ethyl levulinate, EL) are platform chemicals derived from biomass feedstocks that can be converted to a variety of valuable compounds. Reductive amination of levulinates with primary amines and H2 over heterogeneous catalysts is an attractive method for the synthesis of N-alkyl-5-methyl-2-pyrrolidones, which are an environmentally friendly alternative to the common solvent N-methyl-2-pyrrolidone (NMP). In the present work, the catalytic properties of the different nickel phosphide catalysts supported on SiO2 and Al2O3 were studied in a reductive amination of EL with n-hexylamine to N-hexyl-5-methyl-2-pyrrolidone (HMP) in a flow reactor. The influence of the phosphorus precursor, reduction temperature, reactant ratio, and addition of acidic diluters on the catalyst performance was investigated. The Ni2P/SiO2 catalyst prepared using (NH4)2HPO4 and reduced at 600 °C provides the highest HMP yield, which reaches 98%. Although the presence of acid sites and a sufficient hydrogenating ability are important factors determining the pyrrolidone yield, the selectivity also depends on the specific features of EL adsorption on active catalytic sites.

Reductive Amination of 5-Hydroxymethylfurfural to 2,5-Bis(aminomethyl)furan over Alumina-Supported Ni-Based Catalytic Systems.

Mono- and bimetallic Ni-based catalysts were prepared by screening 6 supports and 14 secondary metals for reductive amination of 5-hydroxymethylfurfural (5-HMF) into 2,5-bis(aminomethyl)furan (BAMF), among which γ-Al2 O3 and Mn were the best candidates. By further optimization of the reaction conditions at 0.4 g catalyst loading for 0.5 g substrate of 5-HMF and 160 °C of reaction temperature, 10Ni/γ-Al2 O3 and 10NiMn(4 : 1)/γ-Al2 O3 achieved the highest BAMF yields of 86.3 and 82.1 %, respectively. Although the BAMF yield values were comparable with that over Raney Ni, the turnover frequencies based on the initial BAMF yield and unit weight of Ni for 10NiMn(4 : 1)/γ-Al2 O3 , 10Ni/γ-Al2 O3 , and Raney Ni were calculated as 0.41, 0.09, and 0.04 h-1 , respectively. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that the existence of MnOx well dispersed on the γ-Al2 O3 support and its electron transfer effect with Ni particles on the surface of the support contributed to the high efficiency and better recyclability for the five-time reused 10NiMn(4 : 1)/γ-Al2 O3 catalyst.

Ammonia inhibits energy metabolism in astrocytes in a rapid and glutamate dehydrogenase 2-dependent manner.

Astrocyte dysfunction is a primary factor in hepatic encephalopathy (HE) impairing neuronal activity under hyperammonemia. In particular, the early events causing ammonia-induced toxicity to astrocytes are not well understood. Using established cellular HE models, we show that mitochondria rapidly undergo fragmentation in a reversible manner upon hyperammonemia. Further, in our analyses, within a timescale of minutes, mitochondrial respiration and glycolysis were hampered, which occurred in a pH-independent manner. Using metabolomics, an accumulation of glucose and numerous amino acids, including branched chain amino acids, was observed. Metabolomic tracking of 15N-labeled ammonia showed rapid incorporation of 15N into glutamate and glutamate-derived amino acids. Downregulating human GLUD2 [encoding mitochondrial glutamate dehydrogenase 2 (GDH2)], inhibiting GDH2 activity by SIRT4 overexpression, and supplementing cells with glutamate or glutamine alleviated ammonia-induced inhibition of mitochondrial respiration. Metabolomic tracking of 13C-glutamine showed that hyperammonemia can inhibit anaplerosis of tricarboxylic acid (TCA) cycle intermediates. Contrary to its classical anaplerotic role, we show that, under hyperammonemia, GDH2 catalyzes the removal of ammonia by reductive amination of α-ketoglutarate, which efficiently and rapidly inhibits the TCA cycle. Overall, we propose a critical GDH2-dependent mechanism in HE models that helps to remove ammonia, but also impairs energy metabolism in mitochondria rapidly.

Asymmetric Amination of meso-Epoxide with Vegetable Powder as a Low-Toxicity Catalyst.

This paper describes the scope and limitation of substrates subjected to asymmetric amination with epoxides catalyzed by a soluble soybean polysaccharide (Soyafibe S-DN), which we recently discovered from the reaction of 1,2-epoxycyclohexane with cyclopropylamine. Various meso-epoxides reacted with various amines afforded the corresponding products with good enantiomeric selectivity. Since it was found that pectin was found to have a catalytic ability after screening commercially available polysaccharides, we studied 33 different vegetable powders having pectic substances, and we found that many vegetable powders showed catalytic ability. These results should guide in using vegetable components as low-toxic catalysts for the production of pharmaceuticals.

Dimethyl Labeling-Based Quantitative Proteomics of Recalcitrant Cocoa Pod Tissue.

Dimethyl labeling is a type of stable-isotope labeling suitable for creating isotopic variants of peptides and thus be utilized for quantitative proteomics experiments. Labeling is achieved through a reductive amination/alkylation reaction using the low-cost reagents formaldehyde and cyanoborohydride, resulting in dimethylation of free amine groups of Lys and N-termini. Availability of isotopomeric forms of these reagents allows for the generation of up to six different isotopic variants. Here we describe the application of dimethylation to create two isotopic variants, light and heavy, differing in 4 Da, to label the total tryptic digest peptides of cocoa pod extracted from healthy pods from cultivars susceptible and resistant to the fungal disease called "frosty pod" caused by Moniliophthora roreri.

Natural product-based semisynthesis and biological evaluation of thiol/amino-Michael adducts of xanthatin derived from Xanthium strumarium as potential pesticidal agents.

Xanthatin, a natural sesquiterpene lactone, occurs as one of the major constituents of Xanthium plants (Compositae) and exhibits many important biological properties. To discover natural products-based pesticides, forty-nine Michael-type thiol/amino adducts of xanthatin were synthesized and characterized, while their pesticidal activities were investigated. Among them, compounds 2c, 2h, 2i, and 2t exhibited more potent antifungal activity against Botrytis cinerea (IC50 = 0.96, 0.38, 6.33, and 7.21 µg/mL, respectively) than xanthatin and the two commercial fungicides. Compounds 2t and 2u displayed broad-spectrum and excellent antifungal effects against all tested phytopathogenic fungi, while their IC50 values ranged from 7.21 to 75.88 µg/mL. Compounds 2a, 2f, 2l, 2m, 2v, 7c, 7e, 7h, 7i, and 7j showed moderate larvicidal activity against Plutella xylostella Linnaeus. Furthermore, compounds 2b, 7g, and 7h demonstrated significant ovicidal activity against P. xylostella with the LC50 values of 14.04, 10.00, and 11.95 mg/L, respectively. These findings suggest that thiol/amino appended in the C-13 position of xanthatin may improve antifungal and ovicidal activities for the derivatives. It was also noticed that the exocyclic double bond of xanthatin is crucial for its larvicidal activity. This work also provides some important hints for further design, synthesis, and structural modification of the xanthanolides sesquiterpene lactones toward development of the new environmentally friendly pesticides for sustainable agricultural production.

Design and synthesis of 3-benzylaminocoumarin-7-O-sulfamate derivatives as steroid sulfatase inhibitors.

Steroid sulfatase (STS) is a sulfatase enzyme that catalyzes the conversion of sulfated steroid precursors to free steroid. The inhibition of STS could abate estrogenic steroids that stimulate the proliferation and development of breast cancer, and therefore STS is a potential target for adjuvant endocrine therapy. In this study, a series of 3-benzylaminocoumarin-7-O-sulfamate derivatives targeting STS were designed and synthesized. Structure-relationship activities (SAR) analysis revealed that attachment of a benzylamino group at the 3-position of coumarin improved inhibitory activity. Compound 3j was found to have the highest inhibition activity against human placenta isolated STS (IC50  0.13 µM) and MCF-7 cell lines (IC50 1.35 µM). Kinetic studies found compound 3j to be an irreversible inhibitor of STS, with KI and kinact value of 86.9 nM and 158.7 min-1, respectively.

Generation of amine dehydrogenases with increased catalytic performance and substrate scope from ε-deaminating L-Lysine dehydrogenase.

Amine dehydrogenases (AmDHs) catalyse the conversion of ketones into enantiomerically pure amines at the sole expense of ammonia and hydride source. Guided by structural information from computational models, we create AmDHs that can convert pharmaceutically relevant aromatic ketones with conversions up to quantitative and perfect chemical and optical purities. These AmDHs are created from an unconventional enzyme scaffold that apparently does not operate any asymmetric transformation in its natural reaction. Additionally, the best variant (LE-AmDH-v1) displays a unique substrate-dependent switch of enantioselectivity, affording S- or R-configured amine products with up to >99.9% enantiomeric excess. These findings are explained by in silico studies. LE-AmDH-v1 is highly thermostable (Tm of 69 °C), retains almost entirely its catalytic activity upon incubation up to 50 °C for several days, and operates preferentially at 50 °C and pH 9.0. This study also demonstrates that product inhibition can be a critical factor in AmDH-catalysed reductive amination.

Regulating Transition-Metal Catalysis through Interference by Short RNAs.

Herein we report the discovery of a AuI -DNA hybrid catalyst that is compatible with biological media and whose reactivity can be regulated by small complementary nucleic acid sequences. The development of this catalytic system was enabled by the discovery of a novel AuI -mediated base pair. We found that AuI binds DNA containing C-T mismatches. In the AuI -DNA catalyst's latent state, the AuI ion is sequestered by the mismatch such that it is coordinatively saturated, rendering it catalytically inactive. Upon addition of an RNA or DNA strand that is complementary to the latent catalyst's oligonucleotide backbone, catalytic activity is induced, leading to a sevenfold increase in the formation of a fluorescent product, forged through a AuI -catalyzed hydroamination reaction. Further development of this catalytic system will expand not only the chemical space available to synthetic biological systems but also allow for temporal and spatial control of transition-metal catalysis through gene transcription.

Design, Synthesis and Therapeutic Potential of Some 6, 6'-(1,4- phenylene)bis(4-(4-bromophenyl)pyrimidin-2-amine)analogues.

BACKGROUND: A series of 6, 6'-(1,4-phenylene)bis(4-(4-bromophenyl)pyrimidin-2-amine) derivatives has been synthesized by Claisen-Schmidt condensation and its chemical structures was confirmed by FT-IR, 1H/13C-NMR spectral and elemental analyses. The molecular docking study was carried out to find the interaction between active bis-pyrimidine compounds with CDK-8 protein. The in vitro antimicrobial potential of the synthesized compounds was determined against Gram-positive and Gram-negative bacterial species as well fungal species by tube dilution technique. Antimicrobial results indicated that compound 11y was found to be most potent one against E. coli (MICec = 0.67 µmol/mL) and C. albicans (MICca = 0.17 µmol/mL) and its activity was comparable to norfloxacin (MIC = 0.47 µmol/mL) and fluconazole (MIC = 0.50 µmol/mL), respectively. CONCLUSION: Anticancer screening of the synthesized compounds using Sulforhodamine B (SRB) assay demonstrated that compounds 2y (IC50 = 0.01 µmol/mL) and 4y (IC50= 0.02 µmol/mL) have high antiproliferative potential against human colorectal carcinoma cancer cell line than the reference drug (5- fluorouracil) and these compounds also showed best dock score with better potency within the ATP binding pocket and may also be used lead for rational drug designing.

Microbiota facilitates the formation of the aminated metabolite of green tea polyphenol (-)-epigallocatechin-3-gallate which trap deleterious reactive endogenous metabolites.

The in vivo mechanism of tea polyphenol-mediated prevention of many chronic diseases is still largely unknown. Studies have shown that accumulation of toxic reactive cellular metabolites, such as ammonia and reactive carbonyl species (RCS), is one of the causing factors to the development of many chronic diseases. In this study, we investigated the in vivo interaction between (-)-epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in tea leaves, and ammonia and RCS. We found that EGCG could be oxidized to EGCG quinone in mice, and then rapidly react with ammonia to generate the aminated EGCG metabolite, 4'-NH2-EGCG. Both EGCG and its aminated metabolite could further scavenge RCS, such as methylglyoxal (MGO), malondialdehyde (MDA), and trans-4-hydroxy-2-nonenal (4-HNE), to produce the RCS conjugates of EGCG and the aminated EGCG. Both the aminated and the RCS conjugated metabolites of EGCG were detected in human after drinking four cups of green tea per day. By comparing the levels of the aminated and the RCS conjugated metabolites in EGCG exposed germ-free (GF) mice and specific-pathogen-free (SPF) mice, we demonstrated that gut microbiota facilitate the formation of the aminated metabolite of EGCG, the RCS conjugates of EGCG, and the RCS conjugates of the aminated EGCG. By comparing the trapping capacities of EGCG and its aminated metabolite under aerobic and anaerobic conditions, we found that oxygen is not essential for the trapping of reactive species by EGCG and 4'-NH2-EGCG suggesting that EGCG and its aminated metabolite could scavenge RCS in the GI track and in the circulation system. Altogether, this study provides in vivo evidences that EGCG has the capacity to scavenge toxic reactive metabolic wastes. This finding opens a new window to understand the underlying mechanisms by which drinking tea could prevent the development of chronic diseases.

A selenium-catalysed para-amination of phenols.

Antioxidant enzyme glutathione peroxidase (GPx) decomposes hydroperoxides by utilizing the different redox chemistry of the selenium and sulfur. Here, we report a Se-catalysed para-amination of phenols while, in contrast, the reactions with sulfur donors are stoichiometric. A catalytic amount of phenylselenyl bromide smoothly converts N-aryloxyacetamides to N-acetyl p-aminophenols. When the para position was substituted (for example, with tyrosine), the dearomatization 4,4-disubstituted cyclodienone products were obtained. A combination of experimental and computational studies was conducted and suggested the weaker Se-N bond plays a key role in the completion of the catalytic cycle. Our method extends the selenium-catalysed processes to the functionalisation of aromatic compounds. Finally, we demonstrated the mild nature of the para-amination reaction by generating an AIEgen 2-(2'-hydroxyphenyl)benzothiazole (HBT) product in a fluorogenic fashion in a PBS buffer.

Direct Asymmetric Reductive Amination for the Synthesis of (S)-Rivastigmine.

In this article we demonstrate how asymmetric total synthesis of (S)-rivastigmine has been achieved using direct asymmetric reductive amination as the key transformation in four steps. The route started with readily available and cheap m-hydroxyacetophenone, through esterification, asymmetric reductive amination, N-diphenylmethyl deprotection and reductive amination, to provide the final (S)-rivastigmine in 82% overall yield and 96% enantioselectivity. In the asymmetric reductive amination, catalysed by the iridium⁻phosphoramidite ligand complex and helped by some additives, the readily prepared 3-acetylphenyl ethyl(methyl)carbamate directly reductively coupled with diphenylmethanamine to yield the chiral amine product in 96% ee and 93% yield.

Reductive amination derivatization for the quantification of garlic components by isotope dilution analysis.

In this work, we synthesized internal standards for four garlic organosulfur compounds (OSCs) by reductive amination with 13C, D2-formaldehyde, and developed an isotope dilution analysis method to quantitate these organosulfur components in garlic samples. Internal standards were synthesized for internal absolute quantification of S-allylcysteine (SAC), S-allylcysteine sulfoxide (alliin), S-methylcysteine (SMC), and S-ethylcysteine (SEC). We used a multiple reaction monitoring (MRM) to detect 13C, D2-formaldehyde-modified OSCs by ultrahigh-performance liquid phase chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) and obtained MS spectra showing different ratios of 13C, D2-formaldehyde-modified and H2-formaldehyde-modified compounds. The resulting labeled and unlabeled OSCs were exhibited correlation coefficient (R2) ranged from 0.9989 to 0.9994, respectively. The average recoveries for four OSCs at three concentration levels ranged from 89% to 105%. By 13C, D2-formaldehyde and sodium cyanoborohydride, the reductive amination-based method can be utilized to generate novel internal standard for isotope dilution and to extend the quantitative application.

Preparation of Quenchbodies by protein transamination reaction.

Quenchbody (Q-body) is an antibody fragment labeled with fluorescent dye(s), which functions as a biosensor via the antigen-dependent removal of the quenching effect on fluorophores. It is based on the principle that the fluorescence of the dye(s) attached to the antibody N-terminal region is quenched primarily by the tryptophan residues present in the variable regions, and this quenching is released when the antigen binds to the antibody, resulting in increased fluorescence intensity. Hence Q-body is utilized in various immunoassays for the rapid and sensitive detection of analytes. So far, Q-bodies have been prepared by using a cell-free translation system or by combining Escherichia coli expression and post-labeling steps. However, the above methods need antibody gene cloning, and are time-consuming. In this study, we report a novel approach to prepare Q-bodies by protein N-terminal transamination. We used the antigen-binding fragment (Fab) of an antibody against the bone-Gla-protein (BGP), a biomarker for bone diseases, which was expressed in E. coli. The purified Fab was treated with Rapoport's salt to convert the amino group at the N-terminus to a ketone group, which in turn was allowed to react with fluorescent probes that have aminooxy or hydrazide groups, to prepare a Q-body. The Q-body prepared by this method could detect the BGP-C7 antigen at concentrations as low as 10 nM. Since the approach can label the protein N-terminus directly, it could be applied for preparing Q-bodies from natural antibodies and for the rapid screening of high-performance Q-bodies.

Preparation of Pd/Fe3O4 nanoparticles by use of Euphorbia stracheyi Boiss root extract: A magnetically recoverable catalyst for one-pot reductive amination of aldehydes at room temperature.

We describe a method for supporting palladium nanoparticles on magnetic nanoparticles using Euphorbia stracheyi Boiss root extract as the natural source of reducing and stabilizing agent. The progress of the reaction was monitored using UV-visible spectroscopy. The nanocatalyst was characterized by FE-SEM, TEM, XRD, EDS, FT-IR spectroscopy and ICP. The nanocatalyst was applied as an efficient, magnetically recoverable, highly reusable and heterogeneous catalyst for one-pot reductive amination of aldehydes at room temperature. The nanocatalyst was easily recovered by applying an external magnet and reused several times without considerable loss of activity.

A novel reductive amination method with isotopic formaldehydes for the preparation of internal standard and standards for determining organosulfur compounds in garlic.

Garlic (Allium sativum) is a long-cultivated plant that is widely utilized in cooking and has been employed as a medicine for over 4000 years. In this study, we fabricated standards and internal standards (ISs) for absolute quantification via reductive amination with isotopic formaldehydes. Garlic has four abundant organosulfur compounds (OSCs): S-allylcysteine, S-allylcysteinine sulfoxide, S-methylcysteine, and S-ethylcysteine are abundant in garlic. OSCs with primary amine groups were reacted with isotopic formaldehydes to synthesize ISs and standards. Cooked and uncooked garlic samples were compared, and we utilized tandem mass spectrometry equipped with a selective reaction monitoring technique to absolutely quantify the four organosulfur compounds.

Bioconjugation of Oligodeoxynucleotides Carrying 1,4-Dicarbonyl Groups via Reductive Amination with Lysine Residues.

We evaluated the efficacy of bioconjugation of oligodeoxynucleotides (ODNs) containing 1,4-dicarbonyl groups, a C4'-oxidized abasic site (OAS), and a newly designed 2'-methoxy analogue, via reductive amination with lysine residues. Dicarbonyls, aldehyde and ketone at C1- and C4-positions of deoxyribose in the ring-opened form of OAS allowed efficient reaction with amines. Kinetic studies indicated that reductive amination of OAS-containing ODNs with a proximal amine on the complementary strand proceeded 10 times faster than the corresponding reaction of an ODN containing an abasic site with C1-aldehyde. Efficient reductive amination between the DNA-binding domain of Escherichia coli DnaA protein and ODNs carrying OAS in the DnaA-binding sequence proceeded at the lysine residue in proximity to the phosphate group at the 5'-position of the OAS, in contrast to unsuccessful conjugation with abasic site ODNs, even though they have similar aldehydes. Theoretical calculation indicated that the C1-aldehyde of OAS was more accessible to the target lysine than that of the abasic site. These results demonstrate the potential utility of cross-linking strategies that use dicarbonyl-containing ODNs for the study of protein-nucleic acid interactions. Conjugation with a lysine-containing peptide that lacked specific affinity for ODN was also successful, further highlighting the advantages of 1,4-dicarbonyls.