Journal of Chemistry

Volume 2013 (2013), Article ID 269434, 5 pages

http://dx.doi.org/10.1155/2013/269434

Research Article

Synthesis and Antiviral Activity of Hydrogenated Ferulic Acid Derivatives

Can Cui,¹ Zhi-Peng Wang,¹ Xiu-jiang Du,¹ Li-Zhong Wang,¹ Shu-Jing Yu,¹ Xing-Hai Liu,² Zheng-Ming Li,¹ and Wei-Guang Zhao¹

¹State Key Laboratory of Elemento-Organic Chemistry, National Pesticide Engineering Research Center (Tianjin), Nankai University, Tianjin 300071, China

²College of Chemical Engineering & Materials Sciences, Zhejiang University of Technology, Hangzhou 310014, China

Received 23 January 2013; Accepted 19 March 2013

Academic Editor: Alberto Ritieni

Copyright © 2013 Can Cui et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

A series of hydrogenated ferulic acid amide derivatives 4 were synthesized. The molecular structures of the synthesized compounds were analyzed by NMR and HRMS. The biological activity study showed that some of them displayed excellent protection activity and curative activity against TMV at 500 μg/mL.

1. Introduction

Viruses are among the most agriculturally important groups of plant pathogens, causing serious economic losses in many major crops by reducing yield and quality [1]. Although plant viruses are genetically rather simple, they are difficult to prevent or control and have devastating impact on crop growth. So, plant virus is often referred to as “plant cancer” for several reasons. It is reported that three class pesticides are discovered. For example, nucleoside medicines as ribavirin, tiazofurin, selenazofurin, and benzamide riboside, nonnucleosides such as dufulin and mycophenolic acid, and natural product as ningnanmycin can inhibit virus replication effectively and suppress virus symptoms.

Ferulic acid is isolated from many staple foods, such as fruits, vegetables, cereals, and coffee. It and its derivatives exhibited diversity activity, such as anticancer [2, 3], antiatherogenic [4], anticarcinogenic [5], and antibacterial agents [6], as well as anti-inflammatory activity [7, 8]. In view of these facts mentioned earlier, and also as a part of our work on the synthesis of bioactive lead compounds for drug discovery, the title compounds were designed. We herein report a series of hydrogenated ferulic acid amide derivatives 4 that have been found to possess potent antiviral activities.

2. Results and Discussion

2.1. Chemistry

All of the hydrogenated ferulic acid amide derivatives were prepared from a key intermediate hydrogenated ethyl ferulate, which was easily prepared by catalytic hydrogenation of the ferulic acid 1 using Pd/C and H₂ (1 atm), as shown in Scheme 1. Traditional methods of synthesis of amide suffer from disadvantages, such as long reaction time and inconvenience of handling. In this paper, an eco-friendly and high-yielding method for hydrogenated ferulic acid amides 3 from hydrogenated ethyl ferulate 2 and substituted 2-amino-1-phenylethanol was applied. It can be obtained under microwave irradiation at 130°C in free-solvent conditions for 30 min in generally good yields. As was mentioned earlier, alkylation of the compounds 3 yielded the compounds 4 followed by alkylation with bromoalkane to give the N-(2-alkoxy-2-phenylethyl) hydrogenated ferulic acid amide derivatives 4.

Scheme 1: Reagents and conditions: (i) 10% Pd/C, H₂, EtOH, EA; (ii) isobutyl chloroformate, NMM; (iii) R₁Br, TBAB, NaOH, 65°C.

2.2. Spectrum

In the ¹H NMR spectra of title compounds, the NH proton signals of title compounds were appeared at    ppm. All the alkyl or aryl groups showed the normal location. All the title compounds of HRMS matched with the theoretical values.

2.3. Antiviral Activity

To make a judgment of the antiviral potency of the title compounds, the commercially available plant virucide ribavirin was used as the control. The in vivo antiviral results of all the title compounds against TMV are listed in Table 1. The results showed that title compounds exhibited varying degrees of activities against TMV. Compound 4g displayed good protection activity (22.8%) at 500 g/mL, which is the same of ribavirin at 500 g/mL (32.6%). Compounds 4a and 4f showed the same curative activity level (24.2% and 28.9%, resp.) as ribavirin at 500 g/mL (32.6%).

Table 1: Antiviral activities of the title compounds at 500 μg/mL.

Compound
R₁
R₂
Anti-TMV activities

Protection effect
Curative effect

4a
m-MeO
Benzyl
0
24.2

4b
m-NO₂
Benzyl
10.4
0

4c
m-NO₂
Propynyl
0
0

4d
p-NO₂
Benzyl
0
0

4e
p-benzyloxy
Benzyl
0
12.3

4f
p-benzyloxy
Propynyl
15.2
28.9

4g
p-benzyloxy
Allyl
22.8
20.7

Ribavirin

32.6
38.5

3. Experimental

3.1. Materials and Methods

¹H NMR spectra were measured on a Bruker AC-P500 instrument using TMS as an internal standard and CDCl₃ as solvent. Melting points were determined on an X-4 binocular microscope melting point apparatus (Beijing Tech Instruments Co., Beijing, China) and were uncorrected. HRMS were recorded on an IonSpec 7.0 T Fourier Transform Ion Cyclotron Resonance (FTICR) Mass Spectrometer. All chemicals or reagents were purchased from standard commercial suppliers.

3.2. Synthesis

All of the hydrogenated ferulic acid amide derivatives were prepared as shown in Scheme 1.

To a solution of 3-(3,4-dimethoxyphenyl)acrylic acid (15 g, 72 mmol) in ethyl acetate (150 mL) and ethanol (150 mL), Pd/C (1.5 g, 10%) was added under the N₂ atmosphere. The mixture was refluxed for 72 h. After the reaction was completed, the Pd/C was filtered, and the solvent was evaporated. The combined organic phases were washed with brine, dried over MgSO₄, and evaporated to afford white solid, yield 92%, m.p. 92–94°C (ref. 96–97°C).

To a solution of 3-(3,4-dimethoxyphenyl)propanoic acid (1.44 g, 6.84 mmol) in THF under −20°C, isobutyl chloroformate (0.89 g, 6.84 mmol) and NMM (0.7 g, 7.18 mmol) were added. The mixture was stirred for 30 min. A solution of 2-amino-1-(4-nitrophenyl)ethanol (7.18 mmol) in THF was dropwise in the mixture, then it was stirred for 12 h at room temperature. After the reaction was completed, the THF was evaporated, and the residue was diluted with water and extracted several times with dichloromethane. The combined organic phases were washed with brine, dried over MgSO₄, and evaporated. The remainder was purified by chromatography on silica gel using petroleum ether (60–90°C) and ethyl acetate as the eluent to afford compound 3.

3-(3,4-Dimethoxyphenyl)-N-(2-hydroxy-2-(3-methoxyphenyl)ethyl)propanamide 3a. Yellow solid, yield 85%, m.p. 112–113°C, ¹H NMR (400 MHz, CDCl₃) 2.49 (d,  Hz, 2H, CH₂CH₂), 2.91 (t,  Hz, 2H, CH₂CH₂), 3.32 (s, 1H, ArCHCH₂), 3.69 (s, 1H, ArCHCH₂), 3.83 (s, 9H, p-CH₃O +  p-CH₃O +  p-CH₃O), 4.77 (s, 1H, ArCH), 5.80 (br, 1H, CONH), 7.01–6.67 (m, 6H, Ar-H).

3-(3,4-Dimethoxyphenyl)-N-(2-hydroxy-2-(3-nitrophenyl)ethyl)propanamide 3b. Yellow oil, yield 82%, ¹H NMR (400 MHz, CDCl₃) 2.50 (t,  Hz, 2H, CH₂CH₂), 2.90 (t,  Hz, 2H, CH₂CH₂), 3.30–3.36 (m, 1H, CH₂CH), 3.63–3.68 (m, 1H, CH₂CH), 3.85 (s, 6H, p-CH₃O +  o-CH₃O), 4.90 (dd,  Hz,  Hz, 1H, CH₂CH), 6.03 (br, 1H, CONH), 6.70–6.79 (m, 3H, Ar-H), 7.63–8.20 (m, 4H, Ar-H).

3-(3,4-Dimethoxyphenyl)-N-(2-hydroxy-2-(4-nitrophenyl)ethyl)propanamide 3c. White solid, yield 51%, m.p. 133–135°C, ¹H NMR (400 MHz, CDCl₃) 2.47–2.52 (m, 2H, CH₂CH₂), 2.92 (t,  Hz, 2H, CH₂CH₂), 3.26–3.32 (m, 1H, CH₂CH), 3.66–3.71 (m, 1H, CH₂CH), 3.87 (s, 6H, p-CH₃O +  o-CH₃O), 4.91 (dd,  Hz,  Hz, 1H, CH₂CH), 5.73 (s, 1H, CONH), 6.71–6.81 (m, 3H, Ar-H), 7.45 (d,  Hz, 2H, Ar-H), 8.17 (d,  Hz, 1H, Ar-H).

N-(2-(4-(Benzyloxy)phenyl)-2-hydroxyethyl)-3-(3,4-dimethoxyphenyl)propanamide 3d. Yellow solid, yield 67%, m.p. 132–133°C, ¹H NMR (400 MHz, CDCl₃) 2.45 (t,  Hz, 2H, CH₂CH₂), 2.91 (t,  Hz, 2H, CH₂CH₂), 3.24 (t,  Hz, 1H, ArCHCH₂), 3.80–3.66 (m, 1H, ArCHCH₂), 3.88 (s, 6H, p-CH₃O +  o-CH₃O), 4.22 (d,  Hz, 1H, ArCHCH₂), 4.37 (d,  Hz, 1H, ArCH₂), 4.48 (d,  Hz, 1H, ArCHCH₂), 5.10 (s, 2H, ArCH₂), 5.86 (br, 1H, CONH), 6.84–6.69 (m, 3H, Ar-H), 7.53–7.22 (m, 9H, Ar-H).

RX (7.56 mmol) was added to a mixture of 3 (3.78 mmol), 30% aqueous sodium hydroxide solution (18.9 mmol), and catalytic amount of hexadecyl trimethyl ammonium bromide (0.4 mmol) in 6 mL of CH₂Cl₂ at room temperature. The reaction mixture was heated at reflux for 8 h. Subsequently, the mixture was diluted with water and extracted several times with dichloromethane. The combined organic phases were washed with brine, dried over MgSO₄, and evaporated. The remainder was purified by chromatography on silica gel using petroleum ether (60–90°C) and ethyl acetate as the eluent to afford the title compounds 4a–4g.

N-(2-(Benzyloxy)-2-(3-methoxyphenyl)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4a. Yellow oil, yield 85%, ¹H NMR (400 MHz, CDCl₃) 2.42 (t,  Hz, 2H, CH₂CH₂), 2.88 (t,  Hz, 2H, CH₂CH₂), 3.25–3.16 (m, 1H, ArCHCH₂), 3.77–3.69 (m, 1H, ArCHCH₂), 3.87–3.80 (m, 9H, p-CH₃O + p-CH₃O + o-CH₃O), 4.22 (d,  Hz, 1H, ArCH), 4.38 (dd,  Hz,  Hz, 1H, ArCHCH₂), 4.49 (d,  Hz, 1H, ArCH), 5.81 (s, 1H, CONH), 6.80–6.70 (m, 3H, Ar-H), 6.87–6.81 (m, 3H, Ar-H), 7.38–7.24 (m, 5H, Ar-H). HRMS (ESI) m/z Calcd for C₂₇H₃₁NO₅Na⁺ [M+Na]⁺ 472.2094, found 472.2091.

N-(2-(Benzyloxy)-2-(3-nitrophenyl)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4b. Yellow oil, yield 82%, ¹H NMR (400 MHz, CDCl₃) 2.44 (t,  Hz, 2H, CH₂CH₂), 2.88 (t,  Hz, 2H, CH₂CH₂), 3.28–3.22 (m, 1H, CH₂CH), 3.75–3.72 (m, 1H, CH₂CH), 3.86 (s, 3H, o-CH₃O), 3.88 (s, 3H, p-ArOCH₃), 4.28 (d,  Hz, 1H, Ar-CH), 4.51 (d,  Hz, 1H, Ar-CH), 4.56 (d,  Hz, 1H, CH₂CH), 5.81 (br, 1H, CONH), 6.84–6.72 (m, 3H, Ar-H), 7.43–7.32 (m, 4H, Ar-H), 7.57 (t,  Hz, 1H, Ar-H), 7.67 (d,  Hz, 1H Ar-H), 8.21 (d,  Hz, 1H, Ar-H), 8.27 (s, 1H, Ar-H). HRMS (ESI) m/z Calcd for C₂₆H₂₈N₂O₆Na⁺ [M+Na]⁺ 487.1840, found 487.1835.

3-(3,4-Dimethoxyphenyl)-N-(2-(3-nitrophenyl)-2-(prop-2-yn-1-yloxy)ethyl)propanamide 4c. Yellow oil, yield 95%, ¹H NMR (400 MHz, CDCl₃) 2.40 (m, 3H, CH₂CH₂+ C≡CH), 2.80 (d,  Hz, 2H, CH₂CH₂), 3.22–3.08 (m, 1H, ArCHCH₂), 3.66 (m, 1H, ArCHCH₂), 3.88–3.72 (m, 7H, p-CH₃O +  o-CH₃O + OCH₂CH), 4.09 (m, 1H, OCH₂CH), 4.64 (dd,  Hz,  Hz, 1H, ArCHCH₂), 6.02 (br, 1H, CONH), 6.78–6.61 (m, 3H, Ar-H), 7.46 (s, 1H, Ar-H), 7.56 (s, 1H, Ar-H), 8.24–8.03 (m, 2H, Ar-H). HRMS (ESI) m/z Calcd for C₂₂H₂₄N₂O₆Na⁺ [M+Na]⁺ 435.1527, found 435.1526.

N-(2-(Benzyloxy)-2-(4-nitrophenyl)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4d. Yellow solid, yield 76.8%, m.p. 133–135°C, ¹H NMR (400 MHz, CDCl₃) 2.43 (t,  Hz, 2H, CH₂CH₂), 2.87 (t,  Hz, 2H, CH₂CH₂), 3.19–3.26 (m, 1H, CH₂CH), 3.67–3.73 (m, 1H, CH₂CH), 3.83 (s, 3H, o-ArOCH₃), 3.85 (s, 3H, p-ArOCH₃), 4.26 (d,  Hz, 1H, Ar-CH), 4.47 (d,  Hz, 1H, Ar-CH), 4.54 (dd,  Hz,  Hz, 1H, CH₂CH), 5.86 (br, 1H, CONH), 6.71–6.78 (m, 3H, Ar-H), 7.25–7.38 (m, 5H, Ar-H), 7.50 (d,  Hz, 2H, Ar-H), 8.21 (d,  Hz, 2H,Ar-H). HRMS (ESI) m/z Calcd for C₂₆H₂₈N₂O₆Na⁺ [M+Na]⁺ 487.1840, found 487.1836.

N-(2-(Benzyloxy)-2-(4-(benzyloxy)phenyl)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4e. White solid, yield 68%, m.p. 107-108°C, ¹H NMR (400 MHz, CDCl₃) 2.45 (t,  Hz, 2H, CH₂CH₂), 2.92 (t,  Hz, 2H, CH₂CH₂), 3.30–3.21 (m, 1H, ArCHCH₂), 3.77–3.69 (m, 1H, ArCHCH₂), 3.87 (s, 3H, o-CH₃O), 3.89 (s, 3H, p-CH₃O), 4.23 (d,  Hz, 1H, ArCH₂), 4.38 (dd,  Hz,  Hz, 1H, ArCHCH₂), 4.48 (d,  Hz, 1H, ArCH₂), 5.11 (s, 2H, ArCH₂), 5.83 (br, 1H, CONH), 6.84–6.74 (m, 3H, Ar-H), 7.02 (d,  Hz, 2H, Ar-H), 7.46–7.25 (m, 8H, Ar-H), 7.48 (d,  Hz, 2H, Ar-H). HRMS (ESI) m/z Calcd for C₃₃H₃₅NO₅Na⁺ [M+Na]⁺ 548.2407, found 548.2405.

N-(2-(4-(Benzyloxy)phenyl)-2-(prop-2-yn-1-yloxy)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4f. White solid, yield 68%, m.p. 93-94°C, ¹H NMR (400 MHz, CDCl₃) 2.41 (s, 1H, C≡CH), 2.48 (t,  Hz, 2H, CH₂CH₂), 2.92 (t,  Hz, 2H, CH₂CH₂), 3.13–3.20 (m, 1H, CH₂CH), 3.70–3.78 (m, 1H, CH₂CH), 3.82 (d,  Hz, 1H, OCH₂), 3.86 (s, 3H, o-ArOCH₃), 3.88 (s, 3H, p-ArOCH₃), 4.08 (d,  Hz, 1H, OCH₂), 4.47 (dd,  Hz,  Hz, 1H, CH₂CH), 5.06 (s, 2H, p-ArOCH₂Ph), 5.87 (br, 1H, NH), 6.74–6.81 (m, 3H, Ar-H), 6.96 (d,  Hz, 2H, Ar-H), 7.21 (d,  Hz, 2H, Ar-H), 7.32–7.44 (m, 5H, Ar-CH). HRMS (ESI) m/z Calcd for C₂₉H₃₁NO₅Na⁺ [M+Na]⁺ 496.2094, found 496.2090.

N-(2-(Allyloxy)-2-(4-(benzyloxy)phenyl)ethyl)-3-(3,4-dimethoxyphenyl)propanamide 4g. White solid, yield 65%, m.p. 68-69°C, ¹H NMR (400 MHz, CDCl₃) 2.57–2.41 (m, 2H, CH₂CH₂), 2.92 (d,  Hz, 2H, CH₂CH₂), 3.38–3.15 (m, 2H, CH₂CH), 3.78–3.58 (m, 2H, CH₂CH), 3.97–3.81 (m, 6H, p-CH₃O +  o-CH₃O), 4.74 (d,  Hz, 1H, CH₂CH), 5.07 (s, 1H, CH₂CH), 5.20 (dd,  Hz,  Hz, 1H, CHPh), 5.85 (br, 1H, CONH), 6.87–6.70 (m, 3H, CH=CH₂), 6.96 (s, 1H, Ar-H), 7.53–7.16 (m, 7H, Ar-H). HRMS (ESI) m/z Calcd for C₂₉H₃₃NO₅Na⁺ [M+Na]⁺ 498.2251, found 498.2258.

3.3. Antiviral Activity

3.3.1. Purification of TMV

Using Gooding’s method [9], the upper leaves of Nicotiana tabacum L. inoculated with TMV were selected and ground in phosphate buffer and then filtered through double-layer pledget. The filtrate was centrifuged at 10000 g, treated with PEG twice, and centrifuged again. The whole experiment was processed at 4°C. Absorbance value was estimated at 260 nm by ultraviolet spectrophotometer. Consider

3.3.2. Preparation of Medicaments

Tested compounds and ribavirin used as a reference antiviral agent were first dissolved in minimum volume of N,N-dimethylformamide (DMF) and then diluted with distilled water containing 1% Tween 20 at 500 g/mL concentration.

3.4. Protection Effect of Compounds against TMV In Vivo

The compound solution was smeared on the left side and the solvent serving as control on the right side of growing N. tabacum L. leaves of the same ages. The leaves were then inoculated with the virus after 12 h. A brush was dipped in TMV of  mg/mL to inoculate the leaves, which were previously scattered with silicon carbide. The leaves were then washed with water and rubbed softly along the nervature once or twice. The local lesion numbers appearing 3-4 days after inoculation were counted [10]. There are three replicates for each compound.

3.5. Curative Effect of Compounds against TMV In Vivo

The growing leaves of Nicotiana tabacum L. of the same ages were selected. The tobacco mosaic virus (concentration of  mg/mL) was dipped and inoculated on the whole leaves. The leaves were then washed with water and dried. The compound solution was smeared on the left side, and the solvent was kept on the right side for control. The local lesion numbers were then recorded 3-4 days after inoculation [11]. For each compound, three repetitions were conducted to ensure the reliability of the results, which were measured according to the following formula:

Conflict of Interests

The authors declare that they have no conflict of interests.

Acknowledgments

The authors are grateful to the financial support for this work from the National Natural Science Foundation of China (21172124), the National Basic Research Science Foundation of China (2010CB126105), and the National Key Technologies R&D Program (2011BAE06B05).

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