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Double [3 + 2] cycloadditions for diastereoselective synthesis of spirooxindole pyrrolizidines

  • Xiaofeng Zhang EMAIL logo , Xiaoming Ma , Weiqi Qiu , JohnMark Awad and Wei Zhang EMAIL logo
Published/Copyright: December 19, 2022
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 11 Issue 1

Abstract

One-pot two sequential [3 + 2] cycloadditions of azomethine ylides with different dipolarophiles for diastereoselective synthesis of spirooxindole pyrrolizidines are introduced. This one-pot synthesis involving five components generates a highly condensed ring system bearing seven stereocenters diastereoselectively. The new method has high pot, atom, and step economy. Only two equivalents of water are released as a side product.

Graphical abstract

Keywords: double [3 + 2] cycloaddition; 1,3-dipolar; one-pot; azomethine ylides; pyrrolizidines

1 Introduction

Pyrrolidine, pyrrolizidine, and spirooxindole pyrrolidines are privileged heterocycles found in natural products and synthetic drugs [1,2,3,4] such as supinidine [5], slaframine [6], (−)-isoretronecanol [7,8], hyacinthacine A1 [9], pteropodine [10], spirotryprostatin A [11], and an antibacterial agent [12] (Figure 1). In addition to traditional cyclization [13] and carboamination [14] reactions, [3 + 2] cycloadditions [15,16,17] of stabilized [18,19,20,21], metalated [22,23,24,25], and non-stabilized azomethine ylides are an important approach for the synthesis of pyrrolidine derivatives [26,27,28,29,30,31,32]. We have developed a number of azomethine ylide-based double [3 + 2] cycloadditions for making polycyclic scaffolds (Scheme 1) [33,34,35]. Using different dipolarophiles, such as maleimides or olefinic oxindoles, for inter- and intramolecular [3 + 2] cycloadditions could afford products with fused- and spiro-ring skeletons (Scheme 1a and c) [36,37]. Introduced in this article is a double cycloaddition of stabilized azomethine ylides derived from amino esters and maleimides with olefinic oxindoles to form a spirooxindole-pyrrolizidine scaffold (Scheme 1b).

Figure 1 Bioactive pyrrolidine, pyrrolizidine, and spirooxindole-pyrrolidine compounds.
Figure 1

Bioactive pyrrolidine, pyrrolizidine, and spirooxindole-pyrrolidine compounds.

Scheme 1 Double [3 + 2] cycloadditions with different dipolarophiles: (a) reported synthesis in ref. [35], (b) this work, and (c) reported synthesis in ref. [36].
Scheme 1

Double [3 + 2] cycloadditions with different dipolarophiles: (a) reported synthesis in ref. [35], (b) this work, and (c) reported synthesis in ref. [36].

2 Materials and methods

Amino ester-involved diastereoselective [3 + 2] cycloaddition for making compound I shown in Scheme 1 has been well established [29,31,32,36]. Following the literature procedures [36], the three-component [3 + 2] cycloaddition of glycine methyl ester 2a, N-ethylmaleimide 3a, and 4-bromobenzaldehyde 4a was performed in MeCN under microwave heating at 125°C for 15 min. Without purification, the reaction mixture of adduct 5a was used for the second intermolecular [3 + 2] cycloaddition with 4-bromobenzaldehyde 4a and olefinic oxindole 6a for making product 1a. The reaction conditions including solvents, catalysts, and temperature were screened and optimized. As it has been reported that acids could facilitate the cycloaddition of azomethine ylides [38,39,40]. In this work, the addition of TFA increased the LC yield of 1a from 23% to 73% (Table 1, entries 1–6). Other solvents, such as toluene and EtOH, did not improve the yield (Table 1, entries 7 and 8). Microwave heating at 125°C or 150°C for 1h gave 1a in 37% and 26% LC yields, respectively (Table 1, entries 9 and 10). Replacing TFA with AcOH or BzOH as an acid catalyst did not improve the yield. Thus, the optimized condition for one-pot synthesis was to use 1.1:1.0:2.3:1.0 of 2a:3a:4a:6a in MeCN under microwave heating at 125°C for 15 min for making 5a. The reaction mixture was then reacted with 6a and another equivalent of 4a at 125°C for 18 h in the presence of TFA catalyst to give 1a in 62% of isolated yield as a single diastereomer (Table 1, entry 5). The double [3 + 2] cycloaddition reactions using maleimide and then olefinic oxindole as dipolarophiles effectively assembled spirooxindole-pyrrolizidine 1a with two new rings, six bonds, and seven stereocenters.

Table 1

Double [3 + 2] cycloaddition conditions for 1a

Entry Solvent Acid T (°C) t (h) 1a (%)a
1 MeCN — 90 72 Trace
2 MeCN TFA 90 36 23
3 MeCN TFA 125 36 70
4 MeCN TFA 150 36 67
5 MeCN TFA 125 18 73 (62)
6 MeCN TFA 125 12 61
7 Toluene TFA 125 18 11
8 EtOH TFA 125 18 39
9 MeCN TFA 125b 1 37
10 MeCN TFA 150b 1 26
11 MeCN AcOH 125 18 49
12 MeCN BzOH 125 18 31

aLC yield, isolated yield in parenthesis and conventional heating. bMicrowave irradiation.

3 Results

With the optimized reaction conditions in hand, double [3 + 2] cycloaddition of amino esters 2 with two equivalents of aldehyde 4 and one equivalent each of dipolarophiles 3 and 6 was carried out to afford spirooxindole-pyrrolizidine analogs 1a–g in 53–66% as single diastereomers (Figure 2). However, product 1f was not obtained due to the olefinic oxindole with the Ph instead of CO2R as R1, which may decrease the reactivity of the second cycloaddition.

Figure 2 Double [3 + 2] cycloadditions using two equivalents of same aldehyde 4. Isolated yield: reaction conditions are same as in Table 1, entry 5.
Figure 2

Double [3 + 2] cycloadditions using two equivalents of same aldehyde 4. Isolated yield: reaction conditions are same as in Table 1, entry 5.

Different dipolarophiles 4 and 4′ could be used for the first and second cycloaddition reactions, respectively, to give product 7 with two substitution variations Ar and Ar′. Same procedures for making product 1 shown in Figure 2 were used for the synthesis to afford 7a–h in 49–69% yields (Figure 3). The reaction of thiophene-2-carbaldehyde for the first cycloaddition gave product 7h in 49% yield. However, the reaction of heteroaromatic aldehydes, such as isonicotinaldehyde and furan-2-carbaldehyde, for the second cycloaddition failed to produce 7i and 7j. Product 7k was also not obtained in which the R1 is −COMe instead of −CO2Me.

Figure 3 Double [3 + 2] cycloadditions using different aldehydes 4 and 4′. Isolated yield: reaction conditions are same as in Table 1, entry 5.
Figure 3

Double [3 + 2] cycloadditions using different aldehydes 4 and 4′. Isolated yield: reaction conditions are same as in Table 1, entry 5.

4 Discussion

The one-pot double cycloadditions are diastereoselective to afford products 1 or 7 as single diastereomers. Control experiments were conducted to compare the diastereoselectivity difference of the double cycloaddition reactions with or without intermediate isolation. The cycloaddition with ethyl maleimide as a dipolarophile afforded 5a in 89% yield and 11:1 dr (Scheme 2a), while the reaction with an olefinic oxindole as dipolarophile afforded 8a in 81% yield and 5:1 dr (Scheme 2b). The isolated 5a was then reacted with an olefinic oxindole for the second cycloaddition to afford 1a in 64% and 8:1, but the reaction of 8a with ethyl maleimide failed to give product 9a. The proton at the β-ester group is more acidic, which could lead to the formation of more stable intermediate II, and prevents the cycloaddition of ylide I to form expected product 9a. Compared to the one-pot synthesis of 1a (62% as a single diastereomer) shown in Table 2, the synthesis involving the isolation of intermediate 5a gave 1a in 57% (two steps, dr 8:1). Lower yields and diastereoselectivity for the double cycloadditions involving intermediate isolation were also observed in our previous work [35,37].

Scheme 2 Control reactions. (i) TEA, MeCN, μW 125°C, 15 min, (ii) MeCN, TFA (1.0 equivalent), 125°C, 18 h conventional heating. (a) Pathway for 1a and (b) Pathway for 9a.
Scheme 2

Control reactions. (i) TEA, MeCN, μW 125°C, 15 min, (ii) MeCN, TFA (1.0 equivalent), 125°C, 18 h conventional heating. (a) Pathway for 1a and (b) Pathway for 9a.

The reaction mechanism for the one-pot double cycloadditions and the stereochemistry of the products are proposed in Scheme 3. The first cycloaddition of an acyclic W-shape azomethine ylide with a maleimide is in a suprafacial fashion affords 5- endo diastereoselectively. The stereochemistry of the related intermediates 5 has been confirmed by X-ray structure in our reported double 1,3-dipolar cycloaddition of stabilized azomethine ylides [33,36] to give the final products, which have Ar′ trans with Ar and CO2Me. The second cycloaddition of a cyclic S-shaped azomethine ylide with olefinic oxindole 6 affords product 1 or 7. The diastereoselectivity of the final products generated from the second 1,3-dipolar cycloaddition is similar to the compounds reported in the literature, which have X-ray crystal analysis [41,42,43,44]. The cycloaddition of E-olefinic oxindole and S-shaped azomethine ylide is in an endo fashion (for the C(O)NMe group) to afford the product with CO2Me and CO2Et in trans positions.

Scheme 3 Proposed mechanism for diastereoselective double [3 + 2] cycloadditions.
Scheme 3

Proposed mechanism for diastereoselective double [3 + 2] cycloadditions.

5 Conclusions

In summary, one-pot double [3 + 2] cycloadditions of stabilized azomethine ylides using maleimides and olefinic oxindoles as two different dipolarophiles for diastereoselective synthesis of spirooxindole-pyrrolidine compounds are accomplished. This is a highly efficient reaction process to assemble a polycyclic scaffold with six new bonds and seven stereogenic centers, and only two equivalents of water were generated as a side product. It is a new example of green synthesis that has a good pot, atom, and step economy.

Acknowledgement

The authors thank Jason Evans for performing HRMS analysis.

  1. Funding information: This work was partly supported by the NIH grant T32 CA 236754-1 (Xiaofeng Zhang).

  2. Author contributions: Xiaofeng Zhang: writing – original draft, writing – review and editing, methodology, formal analysis, project administration, data collection, and investigation; Xiaoming Ma and Weiqi Qiu: methodology and formal analysis; JohnMark Awad: writing – review and editing; Wei Zhang: supervision, data investigation, writing – review, and editing.

  3. Conflict of interest: One of the corresponding authors (Wei Zhang) is a member of the Editorial Board of Green Processing and Synthesis.

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Received: 2022-08-09
Revised: 2022-09-25
Accepted: 2022-10-05
Published Online: 2022-12-19

© 2022 Xiaofeng Zhang et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  47. A low-cost and eco-friendly fabrication of an MCDI-utilized PVA/SSA/GA cation exchange membrane
  48. Synthesis, microstructure, and phase transition characteristics of Gd/Nd-doped nano VO2 powders
  49. Biomediated synthesis of ZnO quantum dots decorated attapulgite nanocomposites for improved antibacterial properties
  50. Preparation of metal–organic frameworks by microwave-assisted ball milling for the removal of CR from wastewater
  51. A green approach in the biological base oil process
  52. A cost-effective and eco-friendly biosorption technology for complete removal of nickel ions from an aqueous solution: Optimization of process variables
  53. Protective role of Spirulina platensis liquid extract against salinity stress effects on Triticum aestivum L.
  54. Comprehensive physical and chemical characterization highlights the uniqueness of enzymatic gelatin in terms of surface properties
  55. Effectiveness of different accelerated green synthesis methods in zinc oxide nanoparticles using red pepper extract: Synthesis and characterization
  56. Blueprinting morpho-anatomical episodes via green silver nanoparticles foliation
  57. A numerical study on the effects of bowl and nozzle geometry on performances of an engine fueled with diesel or bio-diesel fuels
  58. Liquid-phase hydrogenation of carbon tetrachloride catalyzed by three-dimensional graphene-supported palladium catalyst
  59. The catalytic performance of acid-modified Hβ molecular sieves for environmentally friendly acylation of 2-methylnaphthalene
  60. A study of the precipitation of cerium oxide synthesized from rare earth sources used as the catalyst for biodiesel production
  61. Larvicidal potential of Cipadessa baccifera leaf extract-synthesized zinc nanoparticles against three major mosquito vectors
  62. Fabrication of green nanoinsecticides from agri-waste of corn silk and its larvicidal and antibiofilm properties
  63. Palladium-mediated base-free and solvent-free synthesis of aromatic azo compounds from anilines catalyzed by copper acetate
  64. Study on the functionalization of activated carbon and the effect of binder toward capacitive deionization application
  65. Co-chlorination of low-density polyethylene in paraffin: An intensified green process alternative to conventional solvent-based chlorination
  66. Antioxidant and photocatalytic properties of zinc oxide nanoparticles phyto-fabricated using the aqueous leaf extract of Sida acuta
  67. Recovery of cobalt from spent lithium-ion battery cathode materials by using choline chloride-based deep eutectic solvent
  68. Synthesis of insoluble sulfur and development of green technology based on Aspen Plus simulation
  69. Photodegradation of methyl orange under solar irradiation on Fe-doped ZnO nanoparticles synthesized using wild olive leaf extract
  70. A facile and universal method to purify silica from natural sand
  71. Green synthesis of silver nanoparticles using Atalantia monophylla: A potential eco-friendly agent for controlling blood-sucking vectors
  72. Endophytic bacterial strain, Brevibacillus brevis-mediated green synthesis of copper oxide nanoparticles, characterization, antifungal, in vitro cytotoxicity, and larvicidal activity
  73. Off-gas detection and treatment for green air-plasma process
  74. Ultrasonic-assisted food grade nanoemulsion preparation from clove bud essential oil and evaluation of its antioxidant and antibacterial activity
  75. Construction of mercury ion fluorescence system in water samples and art materials and fluorescence detection method for rhodamine B derivatives
  76. Hydroxyapatite/TPU/PLA nanocomposites: Morphological, dynamic-mechanical, and thermal study
  77. Potential of anaerobic co-digestion of acidic fruit processing waste and waste-activated sludge for biogas production
  78. Synthesis and characterization of ZnO–TiO2–chitosan–escin metallic nanocomposites: Evaluation of their antimicrobial and anticancer activities
  79. Nitrogen removal characteristics of wet–dry alternative constructed wetlands
  80. Structural properties and reactivity variations of wheat straw char catalysts in volatile reforming
  81. Microfluidic plasma: Novel process intensification strategy
  82. Antibacterial and photocatalytic activity of visible-light-induced synthesized gold nanoparticles by using Lantana camara flower extract
  83. Antimicrobial edible materials via nano-modifications for food safety applications
  84. Biosynthesis of nano-curcumin/nano-selenium composite and their potentialities as bactericides against fish-borne pathogens
  85. Exploring the effect of silver nanoparticles on gene expression in colon cancer cell line HCT116
  86. Chemical synthesis, characterization, and dose optimization of chitosan-based nanoparticles of clodinofop propargyl and fenoxaprop-p-ethyl for management of Phalaris minor (little seed canary grass): First report
  87. Double [3 + 2] cycloadditions for diastereoselective synthesis of spirooxindole pyrrolizidines
  88. Green synthesis of silver nanoparticles and their antibacterial activities
  89. Review Articles
  90. A comprehensive review on green synthesis of titanium dioxide nanoparticles and their diverse biomedical applications
  91. Applications of polyaniline-impregnated silica gel-based nanocomposites in wastewater treatment as an efficient adsorbent of some important organic dyes
  92. Green synthesis of nano-propolis and nanoparticles (Se and Ag) from ethanolic extract of propolis, their biochemical characterization: A review
  93. Advances in novel activation methods to perform green organic synthesis using recyclable heteropolyacid catalysis
  94. Limitations of nanomaterials insights in green chemistry sustainable route: Review on novel applications
  95. Special Issue: Use of magnetic resonance in profiling bioactive metabolites and its applications (Guest Editors: Plalanoivel Velmurugan et al.)
  96. Stomach-affecting intestinal parasites as a precursor model of Pheretima posthuma treated with anthelmintic drug from Dodonaea viscosa Linn.
  97. Anti-asthmatic activity of Saudi herbal composites from plants Bacopa monnieri and Euphorbia hirta on Guinea pigs
  98. Embedding green synthesized zinc oxide nanoparticles in cotton fabrics and assessment of their antibacterial wound healing and cytotoxic properties: An eco-friendly approach
  99. Synthetic pathway of 2-fluoro-N,N-diphenylbenzamide with opto-electrical properties: NMR, FT-IR, UV-Vis spectroscopic, and DFT computational studies of the first-order nonlinear optical organic single crystal
https://doi.org/10.1515/gps-2022-0088
Keywords for this article
double [3 + 2] cycloaddition; 1,3-dipolar; one-pot; azomethine ylides; pyrrolizidines
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Articles in the same Issue

  1. Research Articles
  2. Kinetic study on the reaction between Incoloy 825 alloy and low-fluoride slag for electroslag remelting
  3. Black pepper (Piper nigrum) fruit-based gold nanoparticles (BP-AuNPs): Synthesis, characterization, biological activities, and catalytic applications – A green approach
  4. Protective role of foliar application of green-synthesized silver nanoparticles against wheat stripe rust disease caused by Puccinia striiformis
  5. Effects of nitrogen and phosphorus on Microcystis aeruginosa growth and microcystin production
  6. Efficient degradation of methyl orange and methylene blue in aqueous solution using a novel Fenton-like catalyst of CuCo-ZIFs
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  8. Efficient pilot-scale synthesis of the key cefonicid intermediate at room temperature
  9. Synthesis and characterization of noble metal/metal oxide nanoparticles and their potential antidiabetic effect on biochemical parameters and wound healing
  10. Regioselectivity in the reaction of 5-amino-3-anilino-1H-pyrazole-4-carbonitrile with cinnamonitriles and enaminones: Synthesis of functionally substituted pyrazolo[1,5-a]pyrimidine derivatives
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  13. Aspects of the physiochemical properties of SARS-CoV-2 to prevent S-protein receptor binding using Arabic gum
  14. Sonochemical synthesis of protein microcapsules loaded with traditional Chinese herb extracts
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  16. Fabrication of silicotungstic acid immobilized on Ce-based MOF and embedded in Zr-based MOF matrix for green fatty acid esterification
  17. Superior photocatalytic degradation performance for gaseous toluene by 3D g-C3N4-reduced graphene oxide gels
  18. Catalytic performance of Na/Ca-based fluxes for coal char gasification
  19. Slow pyrolysis of waste navel orange peels with metal oxide catalysts to produce high-grade bio-oil
  20. Development and butyrylcholinesterase/monoamine oxidase inhibition potential of PVA-Berberis lycium nanofibers
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  22. Green synthesis, characterization, cytotoxicity, and antimicrobial activity of iron oxide nanoparticles using Nigella sativa seed extract
  23. Vitamin supplements enhance Spirulina platensis biomass and phytochemical contents
  24. Malachite green dye removal using ceramsite-supported nanoscale zero-valent iron in a fixed-bed reactor
  25. Green synthesis of manganese-doped superparamagnetic iron oxide nanoparticles for the effective removal of Pb(ii) from aqueous solutions
  26. Desalination technology for energy-efficient and low-cost water production: A bibliometric analysis
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  29. Calcium oxide addition and ultrasonic pretreatment-assisted hydrothermal carbonization of granatum for adsorption of lead
  30. Fe3O4@SiO2 nanoflakes synthesized using biogenic silica from Salacca zalacca leaf ash and the mechanistic insight into adsorption and photocatalytic wet peroxidation of dye
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  32. Synergistic in vitro anticancer actions of decorated selenium nanoparticles with fucoidan/Reishi extract against colorectal adenocarcinoma cells
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  35. Integration of microwave co-torrefaction with helical lift for pellet fuel production
  36. Cytotoxicity of green-synthesized silver nanoparticles by Adansonia digitata fruit extract against HTC116 and SW480 human colon cancer cell lines
  37. Optimization of biochar preparation process and carbon sequestration effect of pruned wolfberry branches
  38. Anticancer potential of biogenic silver nanoparticles using the stem extract of Commiphora gileadensis against human colon cancer cells
  39. Fabrication and characterization of lysine hydrochloride Cu(ii) complexes and their potential for bombing bacterial resistance
  40. First report of biocellulose production by an indigenous yeast, Pichia kudriavzevii USM-YBP2
  41. Biosynthesis and characterization of silver nanoparticles prepared using seeds of Sisymbrium irio and evaluation of their antifungal and cytotoxic activities
  42. Synthesis, characterization, and photocatalysis of a rare-earth cerium/silver/zinc oxide inorganic nanocomposite
  43. Developing a plastic cycle toward circular economy practice
  44. Fabrication of CsPb1−xMnxBr3−2xCl2x (x = 0–0.5) quantum dots for near UV photodetector application
  45. Anti-colon cancer activities of green-synthesized Moringa oleifera–AgNPs against human colon cancer cells
  46. Phosphorus removal from aqueous solution by adsorption using wetland-based biochar: Batch experiment
  47. A low-cost and eco-friendly fabrication of an MCDI-utilized PVA/SSA/GA cation exchange membrane
  48. Synthesis, microstructure, and phase transition characteristics of Gd/Nd-doped nano VO2 powders
  49. Biomediated synthesis of ZnO quantum dots decorated attapulgite nanocomposites for improved antibacterial properties
  50. Preparation of metal–organic frameworks by microwave-assisted ball milling for the removal of CR from wastewater
  51. A green approach in the biological base oil process
  52. A cost-effective and eco-friendly biosorption technology for complete removal of nickel ions from an aqueous solution: Optimization of process variables
  53. Protective role of Spirulina platensis liquid extract against salinity stress effects on Triticum aestivum L.
  54. Comprehensive physical and chemical characterization highlights the uniqueness of enzymatic gelatin in terms of surface properties
  55. Effectiveness of different accelerated green synthesis methods in zinc oxide nanoparticles using red pepper extract: Synthesis and characterization
  56. Blueprinting morpho-anatomical episodes via green silver nanoparticles foliation
  57. A numerical study on the effects of bowl and nozzle geometry on performances of an engine fueled with diesel or bio-diesel fuels
  58. Liquid-phase hydrogenation of carbon tetrachloride catalyzed by three-dimensional graphene-supported palladium catalyst
  59. The catalytic performance of acid-modified Hβ molecular sieves for environmentally friendly acylation of 2-methylnaphthalene
  60. A study of the precipitation of cerium oxide synthesized from rare earth sources used as the catalyst for biodiesel production
  61. Larvicidal potential of Cipadessa baccifera leaf extract-synthesized zinc nanoparticles against three major mosquito vectors
  62. Fabrication of green nanoinsecticides from agri-waste of corn silk and its larvicidal and antibiofilm properties
  63. Palladium-mediated base-free and solvent-free synthesis of aromatic azo compounds from anilines catalyzed by copper acetate
  64. Study on the functionalization of activated carbon and the effect of binder toward capacitive deionization application
  65. Co-chlorination of low-density polyethylene in paraffin: An intensified green process alternative to conventional solvent-based chlorination
  66. Antioxidant and photocatalytic properties of zinc oxide nanoparticles phyto-fabricated using the aqueous leaf extract of Sida acuta
  67. Recovery of cobalt from spent lithium-ion battery cathode materials by using choline chloride-based deep eutectic solvent
  68. Synthesis of insoluble sulfur and development of green technology based on Aspen Plus simulation
  69. Photodegradation of methyl orange under solar irradiation on Fe-doped ZnO nanoparticles synthesized using wild olive leaf extract
  70. A facile and universal method to purify silica from natural sand
  71. Green synthesis of silver nanoparticles using Atalantia monophylla: A potential eco-friendly agent for controlling blood-sucking vectors
  72. Endophytic bacterial strain, Brevibacillus brevis-mediated green synthesis of copper oxide nanoparticles, characterization, antifungal, in vitro cytotoxicity, and larvicidal activity
  73. Off-gas detection and treatment for green air-plasma process
  74. Ultrasonic-assisted food grade nanoemulsion preparation from clove bud essential oil and evaluation of its antioxidant and antibacterial activity
  75. Construction of mercury ion fluorescence system in water samples and art materials and fluorescence detection method for rhodamine B derivatives
  76. Hydroxyapatite/TPU/PLA nanocomposites: Morphological, dynamic-mechanical, and thermal study
  77. Potential of anaerobic co-digestion of acidic fruit processing waste and waste-activated sludge for biogas production
  78. Synthesis and characterization of ZnO–TiO2–chitosan–escin metallic nanocomposites: Evaluation of their antimicrobial and anticancer activities
  79. Nitrogen removal characteristics of wet–dry alternative constructed wetlands
  80. Structural properties and reactivity variations of wheat straw char catalysts in volatile reforming
  81. Microfluidic plasma: Novel process intensification strategy
  82. Antibacterial and photocatalytic activity of visible-light-induced synthesized gold nanoparticles by using Lantana camara flower extract
  83. Antimicrobial edible materials via nano-modifications for food safety applications
  84. Biosynthesis of nano-curcumin/nano-selenium composite and their potentialities as bactericides against fish-borne pathogens
  85. Exploring the effect of silver nanoparticles on gene expression in colon cancer cell line HCT116
  86. Chemical synthesis, characterization, and dose optimization of chitosan-based nanoparticles of clodinofop propargyl and fenoxaprop-p-ethyl for management of Phalaris minor (little seed canary grass): First report
  87. Double [3 + 2] cycloadditions for diastereoselective synthesis of spirooxindole pyrrolizidines
  88. Green synthesis of silver nanoparticles and their antibacterial activities
  89. Review Articles
  90. A comprehensive review on green synthesis of titanium dioxide nanoparticles and their diverse biomedical applications
  91. Applications of polyaniline-impregnated silica gel-based nanocomposites in wastewater treatment as an efficient adsorbent of some important organic dyes
  92. Green synthesis of nano-propolis and nanoparticles (Se and Ag) from ethanolic extract of propolis, their biochemical characterization: A review
  93. Advances in novel activation methods to perform green organic synthesis using recyclable heteropolyacid catalysis
  94. Limitations of nanomaterials insights in green chemistry sustainable route: Review on novel applications
  95. Special Issue: Use of magnetic resonance in profiling bioactive metabolites and its applications (Guest Editors: Plalanoivel Velmurugan et al.)
  96. Stomach-affecting intestinal parasites as a precursor model of Pheretima posthuma treated with anthelmintic drug from Dodonaea viscosa Linn.
  97. Anti-asthmatic activity of Saudi herbal composites from plants Bacopa monnieri and Euphorbia hirta on Guinea pigs
  98. Embedding green synthesized zinc oxide nanoparticles in cotton fabrics and assessment of their antibacterial wound healing and cytotoxic properties: An eco-friendly approach
  99. Synthetic pathway of 2-fluoro-N,N-diphenylbenzamide with opto-electrical properties: NMR, FT-IR, UV-Vis spectroscopic, and DFT computational studies of the first-order nonlinear optical organic single crystal
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