Dipeptide Derivatives Research Articles

Synthesis and Biological Evaluation of Amino Acid and Peptide Conjugates of 5-Bromovaleric Acid.

Among various carboxylic acid derivatives, valeric acid or pentanoic acid is found to be widely distributed in nature. It is a straight-chain alkyl carboxylic acid containing five carbon atoms. Due to the therapeutic value of valeric acid, it is used as a versatile nucleus in the pharmaceutical field. Valeric acid derivatives are associated with a broad spectrum of biological activities, like anticonvulsant, antiplatelet, antidiabetic, and plant growth activities. It has previously been revealed that peptide derivatives of carboxylic acids are accountable for enhanced antimicrobial activity. Therefore, it was hypothesized that coupling peptides with valeric acid would increase the antimicrobial properties of the target compounds. So, the objective of the present study was to synthesize peptide derivatives of 5-bromovaleric acid and evaluate their antibacterial and antifungal activities. 5-bromovaleric acid was synthesized by the reaction of cyclopentanone and hydrogen peroxide in the presence of copper bromide and sodium bromide. Additionally, 5-bromovaleric acid was coupled with amino acid methyl esters, dipeptides, tripeptides, and tetrapeptides in the presence of dicyclohexylcarbodimide (DCC) and N-methylmorpholine (NMM) as a base under continuous stirring for 36 hours to produce its peptide derivatives. The results obtained showed that 5-bromovaleric acid possesses more potent antibacterial activity than N-terminal 5-bromovaleric acid conjugates of selected di-, tri, and tetra peptide Cterminal methyl esters against ciprofloxacin as a standard. The selected dipeptide and tripeptide Nterminal 5-bromovaleric acid-conjugated C-terminal methyl ester derivatives were more active than the selected tetrapeptide methyl ester analogue. Using fluconazole as a reference, the antifungal efficacy of 5-bromovaleric acid against C. albicans and A. niger declined as it was combined with C-terminal methyl esters of selected dipeptides, tripeptides, and tetrapeptides. The novel selected peptide derivatives had less antibacterial and antifungal action than the parent 5-bromovaleric acid. Antibacterial and antifungal investigations showed that 5- bromopentanoic acid peptide derivatives might impair antimicrobial efficacy. Further, attaching 5- bromopentanoic acid to di, tri, and tetra peptides did not boost their antibacterial potential.

Interfacial Assembly of Peptide Carbon Dot Hybrids Enables Photoinduced Electron Transfer with Improved Photoresponse.

Assemblies at the interface represent a powerful tool for integrating organic and inorganic components into hybrid nanostructures. Carbon dots are both excellent electron donors and acceptors, offering opportunities for their potential uses in light-harvesting applications. To further improve their functions, integration of acceptor carbon dots into donor organic nanostructures is of great interest for improving photophysical properties useful for photoinduced electron transfer. Here, a one-step protocol for the interfacial assembly of a two-component hybrid consisting of carbon dots and perylene containing an l-phenylalanine-based dipeptide through noncovalent bonding is developed. The perylene-containing dipeptide derivative formed micrometer-long nanofibers on the water surface through J-aggregate formation. Spectroscopic studies reveal photoluminescence quenching of the donor dipeptide upon increasing the concentration of acceptor carbon dots in the hybrid, suggesting photoinduced electron transfer from the donor peptides to acceptor carbon dots. The hybrids integrated in a planar device architecture show a significantly improved photoresponse because of the favorable interactions between the donor-acceptor components. The one-step integration of donor-acceptor hybrids on the water surface offers opportunities for light harvesting and related applications.

Allosteric Inhibition of the β2-Adrenergic Receptor: Design and Synthesis of Cmpd-15 Analogs.

We designed and synthesized 27 new amide and dipeptide derivatives containing a substituted phenylalanine as negative allosteric modulators (NAMs) for the beta-2 adrenergic receptor (β2AR). These analogs aimed to improve the activity of our lead compound, Cmpd-15, by introducing variations in three key regions: the meta-bromobenzyl methylbenzamide (S1), para-formamidophenylalanine (S2), and 1-cyclohexyl-1-phenylacetyl (S3) groups. The synthesis involved the Pd-catalyzed β-C(sp3)-H arylation of N-acetylglycine with 1-iodo-4-substituent-benzenes as the key step. GloSensor cAMP accumulation assay revealed that six analogs (A1, C5, C6, C13, C15 and C17) surpass Cmpd-15 in β2AR allosteric function. This highlights the crucial role of the S1 region (meta-bromobenzyl methylbenzamide) in β2AR allostery while suggesting potential replaceability of the S2 region (para-formamidophenylalanine). These findings serve as a valuable springboard for further optimizing Cmpd-15, potentially leading to smaller, more active, and more stable β2AR-targeting NAMs.

Unraveling the Source of Self-Induced Diastereomeric Anisochronism in Chiral Dipeptides.

Mastering of analytical methods for accurate quantitative determinations of enantiomeric excess is a crucial aspect in asymmetric catalysis, chiral synthesis, and pharmaceutical applications. In this context, the phenomenon of Self-Induced Diastereomeric Anisochronism (SIDA) can be exploited in NMR spectroscopy for accurate determinations of enantiomeric composition, without using a chiral auxiliary that could interfere with the spectroscopic investigation. This phenomenon can be particularly useful for improving the quantitative analysis of mixtures with low enantiomeric excesses, where direct integration of signals can be tricky. Here, we describe a novel analysis protocol to correctly determine the enantiomeric composition of scalemic mixtures and investigate the thermodynamic and stereochemical features at the basis of SIDA. Dipeptide derivatives were chosen as substrates for this study, given their central role in drug design. By integrating the experiments with a conformational stochastic search that includes entropic contributions, we provide valuable information on the dimerization thermodynamics, the nature of non-covalent interactions leading to self-association, and the differences in the chemical environment responsible for the anisochronism, highlighting the importance of different stereochemical arrangement and tight association for the distinction between homochiral and heterochiral adducts. An important role played by the counterion was pointed out by computational studies.

PH-Induced conversion of bolaamphiphilic vesicles to reduction-responsive nanogels for enhanced Nile Red and Rose Bengal delivery

This study details the preparation and investigation of molecular nanogels formed by the self-assembly of bolaamphiphilic dipeptide derivatives containing a reduction-sensitive disulfide unit. The described bolaamphiphiles, featuring amino acid terminal groups, generate cationic vesicles at pH 4, which evolve into gel-like nanoparticles at pH 7. The critical aggregation concentration has been determined, and the nanogels' size and morphology have been characterized through Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Circular Dichroism (CD) spectroscopy reveals substantial molecular reconfigurations accompanying the pH shift. These nanogels enhance the in vitro cellular uptake of the lipophilic dye Nile Red and the ionic photosensitizer Rose Bengal into Human colon adenocarcinoma (HT-29) cells, eliminating the need for organic co-solvents in the former case. Fluorescence measurements with Nile Red as a probe indicate the reduction-sensitive disassembly of the nanogels. In photodynamic therapy (PDT) applications, Rose Bengal-loaded nanogels demonstrate notable improvements, with flow cytometry analysis evidencing increased apoptotic activity in the study with HT-29 cells.

Selective Defluorination of Trifluoromethyl Substituents by Conformationally Induced Remote Substitution

AbstractThe selective reduction of an aromatic trifluoromethyl substituent to a difluoromethyl substituent may be achieved by base‐promoted elimination to form a difluoro‐p‐quinomethide which is trapped by an intramolecular nucleophile. High yields are obtained when the nucleophilic trap entails the conformationally favoured cyclisation of an aminoisobutyric acid (Aib) derivative. The resulting cyclised difluoromethyl‐substituted arylimidazolidinone products are readily converted to versatile difluoromethyl‐substituted aldehydes by reduction and hydrolysis. Defluorination is successful on a range of benzenoid (both para and ortho CF3‐substituted) and heterocyclic substrates. Double defluorination may likewise be achieved sequentially, or in a single step, from an Aib dipeptide derivative.

Selective Defluorination of Trifluoromethyl Substituents by Conformationally Induced Remote Substitution.

The selective reduction of an aromatic trifluoromethyl substituent to a difluoromethyl substituent may be achieved by base-promoted elimination to form a difluoro-p-quinomethide which is trapped by an intramolecular nucleophile. High yields are obtained when the nucleophilic trap entails the conformationally favoured cyclisation of an aminoisobutyric acid (Aib) derivative. The resulting cyclised difluoromethyl-substituted arylimidazolidinone products are readily converted to versatile difluoromethyl-substituted aldehydes by reduction and hydrolysis. Defluorination is successful on a range of benzenoid (both para and ortho CF3-substituted) and heterocyclic substrates. Double defluorination may likewise be achieved sequentially, or in a single step, from an Aib dipeptide derivative.

Postassembly Modification of Peptides by Histidine-Directed β-C(sp3)-H Arylation of Alanine at the Internal Positions: Overcoming the Inhibitory Effect of Peptide Bonds.

Peptide modification by C(sp3)-H functionalization of residues at the internal positions remains underdeveloped due to the inhibitory effect of backbone amides. In this study, using histidine (His) as an endogenous directing group, we developed a novel method for the β-C(sp3)-H functionalization of alanine (Ala) at diverse positions of peptides. Through this approach, a wide range of linear peptides were modified on the side-chain of Ala adjacent to His to afford the functionalized peptides in moderate to good yield and excellent position selectivity. Furthermore, conjugation of peptides with functional molecules such as glucuronide, oleanolic acid, dipeptide, and fluorophore derivatives was achieved.

Co-occurrence network analysis reveals the alterations of the skin microbiome and metabolome in adults with mild to moderate atopic dermatitis.

Skin microbiome can be altered in patients with atopic dermatitis (AD). An understanding of the changes from healthy to atopic skin can help develop new targets for treatment by identifying microbial and molecular biomarkers. This study investigates the skin microbiome and metabolome of healthy adult subjects and lesion (ADL) and non-lesion (ADNL) of AD patients by 16S rRNA gene sequencing and mass spectrometry, respectively. Samples from AD patients showed alterations in the diversity and composition of the skin microbiome, with ADL skin having the greatest divergence. Staphylococcus species, especially S. aureus, were significantly increased in AD patients. Metabolomic profiles were also different between the groups. Dipeptide derivatives are more abundant in ADL, which may be related to skin inflammation. Co-occurrence network analysis of the microbiome and metabolomics data revealed higher co-occurrence of metabolites and bacteria in healthy ADNL compared to ADL. S. aureus co-occurred with dipeptide derivatives in ADL, while phytosphingosine-derived compounds showed co-occurrences with commensal bacteria, for example, Paracoccus sp., Pseudomonas sp., Prevotella bivia, Lactobacillus iners, Anaerococcus sp., Micrococcus sp., Corynebacterium ureicelerivorans, Corynebacterium massiliense, Streptococcus thermophilus, and Roseomonas mucosa, in healthy and ADNL groups. Therefore, these findings provide valuable insights into how AD affects the human skin metabolome and microbiome.IMPORTANCEThis study provides valuable insight into changes in the skin microbiome and associated metabolomic profiles in an adult population with mild to moderate atopic dermatitis. It also identifies new therapeutic targets that may be useful for developing personalized treatments for individuals with atopic dermatitis based on their unique skin microbiome and metabolic profiles.

Design, Molecular Docking, Synthesis, and Antimicrobial Evaluation of new Dipeptide derivatives of Ceftizoxime sodium

Newer cephalosporins that can be orally administered with significant oral bioavailability and resist β-lactamases are continuously and significantly requested. A method of using a potent third-generation cephalosporin, ceftizoxime, was suggested to synthesize new dipeptide derivatives. These derivatives were successfully synthesized by linking a dipeptide moiety, which includes L-Tryptophan-L-valine, L-Tryptophan-L-alanine, L-Tryptophan-L-histidine, and L-Tryptophan-L-phenylalanine as dipeptides to the aminothiazole moiety of ceftizoxime by an amide bond. Their chemical structures were confirmed by spectral analysis, including 1H-NMR,13CNMR, and FT-IR spectroscopy. Molecular docking for these new derivatives was performed on penicillin-binding proteins (PBPs) type 2a (3ZG0) of Methicillin-resistant Staphylococcus aureus, type 2X (5OJ0) of Streptococcus pneumonia and type 1b (5HLA) of E. coli, and has recorded higher affinity binding represented as PLP fitness on target enzymes. The binding scores were significant and may indicate better antimicrobial activities when compared with ceftizoxime. This improvement in affinity binding can be explained by the presence of indole and/or imidazole moieties in those derivatives. The indole and imidazole moieties are actual pharmacophores with various biological activities and may contribute to affinity binding, and the derivatives are considered molecular hybrids. Furthermore, a preliminary evaluation of the antibacterial activity of the synthesized derivatives was performed against two significant bacterial species (MRSA and E. coli), which showed better activity in compression to ceftizoxime. Moreover, the derivatives were tested on the protein oligopeptide (POT) family system and have recorded very interesting results for possible oral absorption when compared with Ceftizoxime, Val-acyclovir, and Val-Val-Acyclovir, as reference drugs. The Swiss ADME server was also used to analyze the pharmacokinetic characteristics and identify those likely to be absorbed orally.

Dihydrolevoglucosenone (Cyrene) as a Biobased Green Alternative to Organic Solvents for the Preparation of Supramolecular Gels Consisting of Self-Assembling Dipeptide Derivatives

Dihydrolevoglucosenone (Cyrene) as a Biobased Green Alternative to Organic Solvents for the Preparation of Supramolecular Gels Consisting of Self-Assembling Dipeptide Derivatives

Interrupted Polonovski Strategy for the Synthesis of Functionalized Amino Acids and Peptides.

The α-functionalization of carbamate-protected hydroxylamine glycine derivatives, acting as imine surrogates via an interrupted Polonovski reaction, is described to access functionalized amino acid derivatives. The addition of C, N, O, and S nucleophiles was achieved in a one-pot procedure in 37% to 92% yield. This method could be extended to dipeptide derivatives for the functionalization of both the C-terminus and N-terminus.

Carica papaya Flower Extracts Possess Antioxidant and 5α-reductase Inhibitory Activities.

Carica papaya has been widely used commercially for skin care due to its therapeutic benefits. The potential of its flower to promote hair growth has been traditionally recognized in other countries but not in the Philippines. In this study, we explored the effect of various extracts of C. papaya flower in the biological activities associated with hair loss, including 5α-reductase inhibition and antioxidation, as well as identified the putative compounds present in the most potent extract. The flowers of C. papaya were macerated separately with ethanol, ethyl acetate, and hexane to obtain their corresponding crude extracts. These extracts were subjected to antioxidant tests via 2,2'-diphenyl-1-picrylhydrazyl (DPPH), and ferric-reducing antioxidant power (FRAP) assays. The total phenolic and flavonoid contents (TPC and TFC) of the crude extracts were determined, as well as the ability of the extracts to inhibit 5α-reductase. The compounds present in the most potent extract were determined using ultraperformance liquid chromatography quadrupole time of flight mass spectrometer (UPLC/MS-QToF). Ethyl acetate extract displayed significantly higher DPPH activity (0.001755 ± 0.00092 ascorbic acid equivalent antioxidant capacity) and 5α-reductase inhibitory activity (115.18 ± 11.61 mg dutasteride/g) compared to ethanol (DPPH: p=0.0121; 5α-reductase: p=0.0016) and hexane (DPPH: p=0.0038; 5α-reductase: p<0.0001) extracts. Similarly, ethyl acetate extract gave the highest FRAP (0.4842 ± 0.0936 mg ascorbic acid/g) activity, TFC (0.0403 mg quercetin/g), and TPC (0.0463 mg gallic acid/g) among the extracts. Forty-nine compounds were annotated in the ethyl acetate extract, with seven (7) putatively identified as fatty acids (9-hydroxy-10,12-pentadecadienoic acid, 9,12,15-octadecatrienoic acid), hydroxyflavone (5-methylkaempferol), alkaloid (allomatrine), dipeptide derivative (aurantiamide acetate), bufotalinin, and 6β-acetoxy-5-epilimonin based on the Traditional Chinese Medicine Library. These results suggest that local C. papaya flowers can be a source of hair growth-promoting agents via their antioxidant and 5α-reductase inhibitory potential.

Coumarin-amino acid hybrids as promising anticancer agents: design, synthesis, docking studies and CK2 inhibition.

A series of mono-peptide, di-peptide and tri-peptide derivatives linked to a coumarin scaffold (5a-c, 7a-c, and 9a-c) were synthesized via the azide-coupling method from corresponding hydrazides 4, 6, and 8. These compounds were tested for anticancer activity against HepG-2, PC-3, and Hct-116 cell lines. Compounds, 7c, and 5b showed significant cytotoxicity, outperforming doxorubicin, with IC50 values of 34.07, 16.06, and 16.02 μM for 7c and 42.16, 59.74, and 35.05 μM for 5b. Compound 7b also displayed promising results with IC50 values of 72.13, 70.82, and 61.01 μM. Moreover, the key structural features of amino acids indicated that mono-peptide and di-peptide derivatives play a key role in increasing their anticancer activities compared with tri-peptides. In addition, the most potent compound 5b also exhibited strong CK2 kinase inhibition with an IC50 value of 0.117 ± 0.005 μM compared with roscovetine as a control drug with an IC50 value of 0.251 ± 0.011 μM. Finally, the binding mode of the chemical inhibitors at the active site of CK2 receptor was also investigated using a docking study which confirmed that the presence of the amino acid functionality is an important feature for anticancer activity and the synthesized compounds showed favorable ADME properties. Besides that, SAR analysis was implemented for the target compounds.

Synthesis and Evaluation of Biological Activities for a Novel 1,2,3,4-Tetrahydroisoquinoline Conjugate with Dipeptide Derivatives: Insights from Molecular Docking and Molecular Dynamics Simulations.

Peptide synthesis has opened new frontiers in the quest for bioactive molecules with limitless biological applications. This study presents the synthesis of a series of novel isoquinoline dipeptides using advanced spectroscopic techniques for characterization. These compounds were designed with the goal of discovering unexplored biological activities that could contribute to the development of novel pharmaceuticals. We evaluated the biological activities of novel compounds including their antimicrobial, antibacterial, and antifungal properties. The results show promising activity against Escherichia coli and potent antibacterial activity against MTCC 443 and MTCC 1688. Furthermore, these compounds demonstrate strong antifungal activity, outperforming existing standard drugs. Computational binding affinity studies of tetrahydroisoquinoline-conjugated dipeptides against E. coli DNA gyrase displayed significant binding interactions and binding affinity, which are reflected in antimicrobial activities of compounds. Our integrative significant molecular findings from both wet and dry laboratories would help pave a path for the development of antimicrobial therapeutics. The findings suggest that these isoquinoline-conjugated dipeptides could be excellent candidates for drug development, with potential applications in the fight against bacterial and fungal infections. This research represents an exciting step forward in the field of peptide synthesis and its potential to discover novel bioactive molecules with significant implications for human health.

A Desmethylphosphinothricin Dipeptide Derivative Effectively Inhibits Escherichia coli and Bacillus subtilis Growth.

New antibiotics are unquestionably needed to fight the emergence and spread of multidrug-resistant bacteria. To date, antibiotics targeting bacterial central metabolism have been poorly investigated. By determining the minimal inhibitory concentration (MIC) of desmethylphosphinothricin (Glu-γ-PH), an analogue of glutamate with a phosphinic moiety replacing the γ-carboxyl group, we previously showed its promising antibacterial activity on Escherichia coli. Herein, we synthetized and determined the growth inhibition exerted on E. coli by an L-Leu dipeptide derivative of Glu-γ-PH (L-Leu-D,L-Glu-γ-PH). Furthermore, we compared the growth inhibition obtained with this dipeptide with that exerted by the free amino acid, i.e., Glu-γ-PH, and by their phosphonic and non-desmethylated analogues. All the tested compounds were more effective when assayed in a chemically-defined minimal medium. The dipeptide L-Leu-D,L-Glu-γ-PH had a significantly improved antibacterial activity (2 μg/mL), at a concentration between the non-desmethytaled (0.1 μg/mL) and the phosphonic (80 μg/mL) analogues. Also, in Bacillus subtilis, the dipeptide L-Leu-D,L-Glu-γ-PH displayed an activity comparable to that of the antibiotic amoxicillin. This work highlights the antibacterial relevance of the phosphinic pharmacophore and proposes new avenues for the development of novel antimicrobial drugs containing the phosphinic moiety.

In vitro study on antitumor activity of aurantiamide acetate extracted from Polygonum capitatum

Aurantiamide acetate is a dipeptide derivative with antibacterial, antiviral, anti-inflammatory and analgesic activities. However, its antitumor activity has not been documented. This study aimed to prepare aurantiamide acetate from Polygonum capitatum and investigate its antitumor activity in vitro. The petroleum ether extract fraction of 80% ethanol extract from P. capitatum was separated by silica gel column chromatography. Aurantiamide acetate was obtained and identified by physicochemical properties, MS and NMR spectral data. The inhibitory effect of different doses of this compound on the proliferation of human umbilical vein endothelial cells (HUVECs), human gastric cancer BGC-823 cells, lung cancer A549 cells and colorectal cancer Caco-2 cells was detected by CCK-8 method. Morphological changes of BGC-823 cells were observed under the inverted microscope. The effect of aurantiamide acetate on BGC-823 apoptosis and cycle was detected by flow cytometry. The expression of Bax and caspase-3 in BGC-823 cells was detected by Western blotting. Aurantiamide acetate inhibited BGC-823, A549 and Caco-2 cell proliferation at the concentrations from 25 μmol/L to 100 μmol/L, but had no inhibitory effect on HUVECs at the concentrations from 12.5 μmol/L to 100 μmol/L. The inhibitory effect of Aurantiamide acetate was most pronounced on BGC-823 cell proliferation at IC50 of 56.73 μmol/L, most probably by increasing the protein expression of caspase-3 and Bax in BGC-823 cells, and arresting cell cycle in G2/M phase. This is the first time that we isolated aurantiamide acetate from P. capitatum with a purity of 98.21%, and found that Aurantiamide acetate could in inhibit the proliferation of various cancer cell types in vitro. This finding may provide a new resource for developing anti-tumor drugs in future.

Design and synthesis of novel carbohydrate-amino acid hybrids and their antioxidant and anti-β-amyloid aggregation activity

Herein we report the synthesis of new furanoid sugar amino acids and thioureas, prepared by coupling aromatic amino acids and dipeptides with isothiocyanato- functionalized ribofuranose ring. Since carbohydrate-derived structures possess many biological activities, synthesized compounds were evaluated as anti-amyloid and antioxidant agents. The anti-amyloid activity of the studied compounds was evaluated based on their potential to destroy amyloid fibrils of intrinsically disordered Aβ40 peptide and globular hen egg-white (HEW) lysozyme. The destructive efficiency of the compounds differed between the studied peptides. While the destruction activity of the compounds on the HEW lysozyme amyloid fibrils was negligible, the effect on Aβ40 amyloid fibrils was significantly higher. Furanoid sugar α-amino acid 1 and its dipeptide derivatives 8 (Trp-Trp) and 11 (Trp-Tyr) were the most potent anti-Aβ fibrils compounds. The antioxidant properties of synthesized compounds were estimated by three complementary in vitro assays (DPPH, ABTS, and FRAP). The ABTS assay was the most sensitive for assessing the radical scavenging activity of all tested compounds compared to the DPPH test. Significant antioxidant activity was detected for compounds in the group of aromatic amino acids depending on the present amino acid, with the highest activity in the case of dipeptides 11 and 12 containing the Tyr and Trp moiety. Regarding the FRAP assay, the best reducing antioxidant potential revealed Trp-containing compounds 5, 10, and 12.

Synthesis and Study of Anticancer and Antioxidant Activities of 2-oxoquinoline Hydrazide Derivatives

In this work, hydrazone, thiosemicarbazide, diamide, and dipeptide derivatives were prepared from the glycine and β-alanine hydrazide of 4-hydroxy-2-oxoquinoline. The desired derivative resulted from substitution, hydrazinolysis, condensation, and azide coupling reactions. The fabricated derivatives were screened for anticancer characteristics toward human’s colon carcinoma (HCT-116) cell line using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide viability assay, while antioxidant property was examined using an in vitro H2O2 scavenging method. The β-alanine hydrazide derivative 3a showed a remarkable IC50 value of 18.8 μg/mL, whereas its corresponding thiosemicarbazide 5b exhibited moderate activeness with an IC50 value of 26.89 μg/mL. Conversely, the dipeptide derivative 7 with a Gly-β-Ala sequence showed better activity than the β-Ala-Gly derivative 8a. The IC50 values of 27.28 and 61.4 μg/mL, respectively, were achieved. According to an H2O2 scavenging activity test, the hydrazide of β-Ala derivative 2a displayed the best H2O2 scavenging property, with an IC50 value of 38.7 μg/mL.

Synthesis of optically active SARS-CoV-2 Mpro inhibitor drug nirmatrelvir (Paxlovid): an approved treatment of COVID-19.

Nirmatrelvir (Paxlovid) is an FDA approved drug that targets SARS-COV-2 3CLprotease. We report an optically active synthesis of nirmatrelvir that avoids a critical epimerization step. Our initial coupling of gem-dimethyl bicyclo[3.1.0]proline methyl ester with tert-leucine-trifluoroacetamide using standard coupling reagents, EDC and HOBt, provided the corresponding dipeptide derivative in excellent yield, however, a significant epimerization was observed at the tert-leucine bearing chiral center. To circumvent this epimerization problem, we developed a ZnCl2-mediated direct N-trifluroacetylation of Boc-derivatives for the synthesis of nirmatrelvir. This protocol has been utilized for N-acyl bond formation with other anhydrides without epimerization. The present synthetic route can be useful for the synthesis of structural variants of nirmatrelvir without significant epimerization.