Carbazole alkaloids have a fragrant tricyclic bone structure composed of a ring central pyrrole intertwined between two benzene rings. Due to the intriguing structural properties and promising therapeutic properties of these natural product, great strides have been made in the carbazole alkaloids field [1,2]. Heterocycles are a subclass of pharmacologically active compounds. Carbazoles, especially naturally occurring carbazole, have significant anti-cancer properties. For example, in 1965, Chakraborty isolated the first natural product of carbazole, murrayafoline A, from the Murraya koenigii tree; Murrayafoline A is an antibiotic  and an antitumor product . Carbazole products are used in a wide range of high-tech applications, including organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), dye solar cells (DSSCs), and sensors [5,6]. Carbazoles have been extensively studied for its biological properties, including antimicrobial , antiprotozoal , and pesticide activity, as well as anti-inflammatory [9,13], antiviral , antifungal , antibacterial , anti-inflammation , antioxidative , antiplatelet aggregative , and neuroprotective activity . Three carbazole alkaloids, O-methylmukonal, 3-formyl-2,7-dimethoxycarbazole, and clauszoline-J, demonstrated promising anti-HIV-1 activity, with EC50 values of 2.7, 7.4, and 8.2 µg/mL, respectively, and PTI values of 56.7, 8.0, and 1.6, respectively .
Materials and procedures
All starting chemical compounds were obtained from Fluka or Aldrich. Using Gallenkamp and a Thomas capillary freezing point apparatus, melting points (MP) were determined in open glass capillaries and they were uncorrected. SHIMAZU INFRARED -8400 Fourier transform infrared spectrophotometer used the KBr disc's INFRARED spectra. Purified and commercially available primary components and reagents were employed in their entirety. To record 1H-NMR and 13C-NMR spectra, a 500 MHz spectrometer was used. Agilent technologies model ultrashield nuclear resonance (NMR) spectra were acquired in dimethyl sulfoxide (DMSO-d6), and chemical shifts are given in (ppm) downfield using tetramethylsilane (TMS) as a reference. UV-vis spectra were acquired with a shimadzu spectrophotometer and an Apel PD-303 spectrophotometer, both made in Japan.
α-Chloro-N-carbazoleacetamide preparation (1) 
The carbazole compound solution (1.5 gram, 0.009 mole) in dry dimethylformamide (6 mL) was cooled to 0 ℃ and NaH (0.21 gm., 0.009 mol) was added to the solution in small amount on a periodic basis. Chloroacetyl chloride (0.66 mL, 0.009 mol) was added via syringe to the slurring and the mixture reaction was gradually brought to a temperature comparable to that of the surrounding air. After 14 hours, the reaction was quenched with water from the ethanol solvent via filtration and recrystallization. The table below summarizes the physical properties and IR absorption bands of the material (1).
α-Hydrazino -N- carbazoleacetamide preparation (2) 
In absolute ethanol, 1.5 gm of compound (1) (0.006 mol.) and 0.75 mL of hydrazine hydrate (0.012 mole.) were dissolved with constant stirring. After cooling the mixture, a white precipitate formed after it was refluxed in a water bath for 5 hours. Precipitate was present in the filtrate. The following table summarizes the product's physical and infrared spectral properties (1).
Preparation of α-hydrazino-N-carbazoleacetamide Schiff base derivatives (3-8) 
Two to three drops of glacial acetic acid were added to the hot stirred solution of the hydrazide (2) (0.5 gm, 0.002 mol) in ethanol (5 mL). The para-substituted aromatic aldehyde (0.002 moles) added at (70-80) ºC for (4-6) hours were used to heat the reaction mixture. Filtration was used to remove any remaining liquid from the separated solid. The physical properties and FTIR spectral properties are listed in Table 2.
N- [3-chloro-4-(4-substituted phenyl)-2- oxoazetidine-1-yl) amino] aceto- 9H-carbazol-9-yl) (9-14) 
At 0-5 °C, a solution of Schiff bases (3-8) (0.001 mole.) in dry DMF (5 mL) was added to solutions of chloroacetyl chloride (0.086 mL, 0.001 mole.) and trimethylamine (0.15 mL, 0.001 mole) in dry DMF (3 mL). After refluxing the mixture at 110 °C for (14-16) hours, it was cooled to room temperature. The product compound (9-14) was rinsed with cold water & recrystallized using an appropriate solvent. The physical properties, infrared spectral and yield of compounds are listed in Table 3.
Synthesis of N- [2-oxo-3-phenyl-4-(4-substituted phenyl-1,3-diazetidine-1-yl amino) acetamide] carbazol-9-yl. (15-20)
N- [(2-oxo-3-phenyl-4-(4-substituted phenyl)- 1,3- diazetidine-1-yl) amino) aceto] carbazol-9-yl)- 2-thione. (20-26) 
Mixture of Schiff base (3-8) (0.02mol) with dry DMF (12 mL) (phenyl isocyanate, phenylisothiocyanate) (0.02 mol) was added in few amounts with continuous stirring also, the mixture was gradually heated, then refluxed for (6-7) hours. Then, it was filtered and dried. Physical properties of compounds (15-26) and INFRARED spectral are shown in Table 4.
Antioxidant activity (DPPH radical scavenging assay)
The antioxidant activity of compounds (1-26) was assessed using the stable DPPH free radical according to a known procedure . Three different concentrations 100, 200 and 400 μg/mL of the synthesized compounds (1-26) were mixed with EtOH solution (up to 2mL) including 0.0002 μg/mL of DPPH. The absorbance of the reaction mixture was measured at 517 nm after incubation for 30 min at room temperature, using spectrophotometer. Ascorbic acid was used as a control at the same concentrations of the tested compounds. Percentage inhibitions of compounds (1-26) and that of ascorbic acid were calculated using the following formula:
DPPH inhibition effect7 (%) =((Ac-As)/Ac) *100
Ac=Absorbance reading of the control
As=Absorbance reading of the sample
Results and discussion
In this research, new α-Chloro-N-carbazole acetamide (1), α-hydrazino-N- carbazole acetamide (2), it’s Schiff bases derivatives (3-8), and β-Lactams (9-14), 1,3-diazetidine (15-26) were synthesized, as shown in Scheme 1.
Carbazole reaction with sodium hydrate and chloroacetylchloride to give compound (1) was confirmed by physical properties which are listed in Table 1. Infrared spectral data showed the absorption at 3051 and 2923, 2854 cm-1 for ν (C-H Aromatic and ʋ C-H alpha.) respectively 1699 cm-1 for ʋ (C=O) amide  750 cm-1 for (C-Cl). The compound (1) reacted with hydrazine hydrate to give α-hydrazino-N-carbazole acetamide (2). FITR spectrum data showed absorption at 3440, 3051, (2923, 2852), 3440 overlap, 3315 cm-1 could be attributed to N-H, ʋ C-H Aromatic and ʋ C-H Alpha. ʋ NH2 Asym. and Sym. Respectively and 1680 cm-1 for ʋ (C=O). While the 1H-NMR spectra data of compound (2) ppm in DMSO-d6 solvent  shown in Table (5) (3.25) (s,2H, -COCH2-); 4.25 (s,2H, NH2); 7.1-7.5 (m,8H, Ar-H); 8.13 (s,1H, -NH-). 13C-NMR spectra for compound (2) shown in Table 6. The Schiff bases (3-8) were synthesized by condensation reaction of α-hydrazino-N-carbazole acetamide (2) with different substituted aromatic aldehydes with a little drop of glacial acetic acid in absolute ethanol to form Schiff’s bases (3-8) (Scheme 1). The sterchaning absorption bands showed at (3465- 3380) cm-1 for ʋ(N-H) and confirmed the formation of compound (3-8) from the appearance of the bands at (1660-1650) cm-1 to ʋ (N=C) of Schiff’s, bases (3-8), respectively . With the disappearance of ʋ (NH2), all details of infrared spectral data to compounds (3-8) were in Table 2. 1H-NMR spectrum of compound 7 was shown in Table 5, a singlet signal at δ= (3.38) ppm for (O=C-CH2) proton, a singlet signal at δ = (6.80) ppm due to (-NH-N -) proton, multiplate signal at δ = (7.16-8.18) ppm is due to aromatic rings (Ar-H) protons, a singlet signal at δ = (8.60) ppm due to(-N=CH-). 1H-NMR spectrum of compound (8) shown in Table 5, 3.23 (s,6H, N(CH3)2), 3.37), 3.37 (s,2H, O=C-CH2), 6.81 (s,1H, -NH-N), -NH-N), 7.15-8.18 (m,12H, Ar -H), 8.52 (s,1H, N=CH). 13C-NMR spectra for compound (7,8) shown in Table 6.
Schiff bases (3-8) were reacted with chloroacetyl chloride followed by the addition of triethylamine to produce the compounds of N- [3-chloro-4-(4-substituted phenyl)-2-oxoazetidene-1-yl) amino] aceto-9H-carbazol-9-yl) (9-14). The structure of azetidine-2-one has been confirmed by infrared spectroscopy. Infrared spectrum for compound (9-14) showed the appearance of the absorption band (3480, 3440, 3420, 3365, 3350, 3340) cm-1 for ʋ(N-H), (1701-1679) cm-1 and at (1683-1650) cm-1 for the ʋ(C=O) amide. Every detail of a compound's infrared spectral data (9-14) was indicated in Table 3. Table 7 shows the 1H-NMR spectrum of compound 9 at a signal of singlet δ = (3.23) ppm for (H2 C-C=O) protons, at a signal of singlet δ = (4.40) ppm to (-CH-Cl azetidine ring) protons, at a signal of singlet δ = (4.80) ppm for (-CH azetidine ring), at a signal of singlet δ = (6.80) ppm to (-NH-N) protons, multiplate signals at δ = (7.15-8.19) ppm are Ar-H due to aromatic rings protons, 1H-NMR spectrum of compound (10) shown in Table 7, at a signal of singlet δ = (3.39) ppm due to (H2 C-C=O) protons, at a signal of singlet δ = (4.60) ppm for (-CH-Cl azetidine ring), at a signal of singlet δ=(5.00) ppm for (-CH azetidine ring), at a signal of singlet δ = (6.89) ppm to (-N-NH-) protons, at δ = (S, 7.16-8.18) ppm Ar-H to protons in aromatic rings, at signal of singlet δ=(8.90) ppm to (-OH) protons. Data for the compounds (9,10) 13C-NMR spectroscopy are shown in Table 8.
Schiff bases (3–8) react with phenyl isocyanate and phenyl isothiocyanate in dry DMF under reflux to form 1,3-diazetidine (15–26). The structure of 1,3-diazetidine derivatives has been definite by infrared spectroscopy. Infrared spectrum of the synthesized compounds (15-20) for phenyl isocyanate showed ʋ (N-H) at (3332-3298) cm-1, (1699-1672) cm-1 and at (1673-1660) cm-1 for the ʋ(C=O) amide.
1H-NMR spectrum of compound (17) has been shown in Table 7 at a signal of singlet δ = (3.22) ppm to (-CH3 )protons, at signals of singlet δ = (3.36) ppm to(H2C-C=O )protons, at a signal’s of singlet δ = (4.45) ppm, for (-CH diazetidine ring), at a signal of singlet δ = (6.99) ppm is due to (-NH-N-) protons, a signals at δ = (7.15-8.67) ppm (Ar-H) due to aromatic rings protons. 1H-NMR spectrum of compound (18) has been shown in Table (7) at a signal of singlet δ = (3.40) ppm for (H2C-C=O) protons, at signal of singlet δ= (5.65) ppm for (-CH diazetidine ring), at a signal of singlet δ = (6.99) ppm is due to (-NH-N) protons, a signal at δ = (7.15-8.68) ppm (Ar-H) due to aromatic rings protons. 13CNMR spectral data of compound (17,18) is shown in Table 8. Infrared spectrum for compounds (20-26) for phenyl isothiocyanate showed ʋ (N-H) at (3461-3205) cm-1 and bands of ʋ (C=O) at (1699-1679) cm-1, in addition to the disappearance bands of ʋ (N=C) with appearance of ʋ(C=S) at (1452-1450) cm-1. Infrared spectral data for compounds (15-26) is listed in a Table 4 that includes all information. 1H-NMR spectrum of compound (21) shown in Table 7 showed at a signal of singlet δ = (3.38) ppm to (O=C-CH2) protons, a signal of singlet δ = (5.63) ppm for (-CH diazetidine ring), at a signal of singlet δ = (6.90) ppm is to (-NH-N) protons, a signal at δ = (7.16-8.44) ppm (Ar-H) for aromatic rings protons. 1H-NMR spectrum of compound (26) shown in Table 7; at a signal of singlet δ = (3.05) ppm to N(CH3)2 protons, at a signal of singlet δ = (3.36) ppm to(H2C-C=O) protons at a signal of singlet δ = (5.50) ppm for (H-C- diazetidine ring), at a signal of singlet δ = (6.81) ppm is to (-N-NH-) protons, a signals at δ = (7.12-8.13) ppm (Ar-H) to aromatic rings protons. 13C-NMR spectral data of compounds (21,26) was shown in Table 8.
Antioxidants are critical compounds that inhibit or neutralize free radicals, thereby protecting cells from oxidative damage . As with any other radical chain reaction, autoxidation consists of three steps: initiation, propagation, and termination . As a result, the development of effective antioxidant agents requires sufficient attention during the drug design and discovery process . The antioxidant activity of the compounds was determined in vitro using DPPH scavenging activity.
DPPH scavenging activity
All the compounds (1-26) and starting carbazole showed comparable or slight less activity to the standard (ascorbic acid). It was predestined by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay method at various concentrations (100 ,200 and 400 µg/mL). The compound is known as an antioxidant or a non-antioxidant by changing the color of the compound (DPPH) from violet to colorless, or there is a change in the color of the compound (DPPH), and this change depends on the color of the compound used. The compound is considered an antioxidant if there is a change in color (DPPH). Compounds (3,4,5,7,9,10,11,13,15,18 ,21,22,24, 25,26) exhibited the best results among all compounds. Some compounds (3,9,15,21) bearing a nitro group (electron withdrawing group) at para position showed high antioxidant activity when compared to some compounds that have methoxyl group (electron donating group). Compounds (7,13,25) substituted with halogen groups –Cl (electron withdrawing group) exhibit good antioxidant activity. Compounds that showed less antioxidant activity are (1,2,6,8,12,14,20) and carbazole. These compounds possessed good reducing power ability at medium concentration (200 µg/mL) among other compounds and exhibited close or higher antioxidant activity than the standard solution (ascorbic acid). Figure 1 represented the DPPH scavenging activity of the newly synthesized compound.
New β-lactam derivatives were synthesized and identified by [FT-IR, 1H-NMR & 13C-NMR], physical and chemical properties, all this new synthesis of carbazole derivatives were studied in-vitro antioxidant activity; the results display that test had a good biological activity.
I would like to thank all member staff of the department of Chemistry, University of Baghdad.
How to cite this article: Mohammed Hasan Mohammed AL-Dahlaki, Suaad M.H. Al-Majidi. The synthesis, identification, and evaluation of some new antioxidant activities β-lactam from N-carbazole derivatives. Eurasian Chemical Communications, 2022, 4(3), 209-221. Link: http://www.echemcom.com/article_144206.html
Copyright © 2022 by SPC (Sami Publishing Company) + is an open access article distributed under the Creative Commons Attribution License(CC BY) license (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.