English

• 1. INTRODUCTION

  As an abundant forest resource in China, rosin has been deeply processed and widely used in many fields to date^[1-3]. Dehydroabietic acid (DA), a major component of the natural tricyclic diterpene resin acids, can be readily obtained from the commercial disproportionated rosin^[4]. Compared to other resin acids, DA is more suitable to be a precursor to synthesize rosin-based derivatives due to its stable phenyl group of the tricycle. In recent years, DA and its synthetic derivatives have gradually attracted more and more interest because of their broad potential applications in the fields of biology, medicine, optics, and surfactants^[5-7]. At present, the research on DA and its derivatives targets mainly to antimicrobial, antiviral, antitumor, antioxidant, and other biological activities^[8-14], while, the studies into other applications are somewhat neglected. Hence, the synthesis of DA-based derivatives together with the exploration of their potential applications is one of our research focus in recent years. Ferrocene (Fc) has been widely used because of its remarkable stability, easy modification, redox reversibility and radiation resistance, leading to its wide applications in medicine^[15-17], non-linear optics^[18-20], electrochemistry^{[21, 22]}, and organic magnetic materials^[23] in recent years. Owing to its unique sandwich structure and high electron-rich system, Fc and its derivatives have good electrochemical properties, which could easily undergo a reversible one-electron redox process^{[19, 24, 25]}. We have previously synthesized a DA-Fc anhydride with good redox performance^[26]. In continuation of our researches on DA derivatives with the pursue of good electrochemical properties, Fc is incorporated into the known dehydroabietylamine (DAA) as well as another newly synthesized DA-based amine via Schiff base reactions. In this study, we report the syntheses, characterizations, and crystal structures of the title compounds. Additionally, the results of electrochemical properties are also presented.

  2. EXPERIMENTAL

  2.1 General procedures and materials

  N-Bromosuccinimide (NBS, Aladdin, 99%), iron powder (Energy Chemical, 99%), pyrrolidine (Aladdin, 99%), and chloroform-d₃ (CDCl₃, J&K Scientific, 99.8%) were purchased from their respective companies and used as received. Thionyl chloride (SOCl₂), benzene, and other organic solvents were purchased from Nanjing Chemical Reagent Co., Ltd. and used without further purifications. Ferrocenecarboxaldehyde (Fc-CHO, Aladdin, 98%) was purified by recrystallization from ethanol and dried under vacuum before use.

  Dehydroabietic acid was obtained via reported purification procedures of commercially disproportionated rosin (Guangxi Jinxiu Songyuan forest products Co., Ltd.)^[4]. Dehydroabietylamine was purified from commercially disproportionated rosin amine (Hubei Xinmingtai Chemical Co., Ltd.) as reported in the literature^[27]. Reactions were monitored by TLC silica gel 60 F₂₅₄ sheets from Taizhou Biochemical Plastic Factory, China and detected under UV light (254 and 365 nm). Purifications were performed by flash chromatography on silica gel (300~400 mesh) from Qingdao Marine Chemical Factory, China. Melting points were determined on an OptiMelt MPA100 apparatus (SRS, USA) without correction. FT-IR spectra were recorded on a Thermo Nicolet 380 FT-IR spectrometer (Thermo Electron, USA) with KBr methods in the 4000~500 cm^-1 range. High-resolution mass spectra (HRMS) were recorded using a Finnigan MAT TSQ 7000 Mass Spectrometer System operated in a MALDI-TOF mode. NMR measurements were performed on a Bruker AVANCE-Ⅲ-600 spectrometer (¹H, 600.13 Hz; ¹³C, 150.92 Hz) with CDCl₃ as solvent unless otherwise stated. Chemical shifts were given as parts per million (ppm) and referenced to the solvent as an internal standard. J values were given in Hz. Elemental analyses (C, H and N) were performed on a 2400 Ⅱ elemental analyzer (PE, USA). Cyclic and differential pulse voltammograms were recorded in a 0.10 M [n-Bu₄N][PF₆] solution (CH₂Cl₂ as solvent) on a CHI 660E electrochemical analyzer with a glassy carbon working electrode, a platinum plate auxiliary electrode, and a Ag/AgCl reference electrode. The concentration of all the samples was 2.0 mM, and all the potential values were referenced to Fc/Fc⁺.

  2.2 Syntheses

  2.2.1   Synthesis of DAMBA-Fc

  DAMBN was synthesized from DA according to the procedures previously reported^[28], which was further treated as the precursor to afford DAMBA and DAMBA-Fc, consecutively (Scheme 1). To a solution of DAMBN (198 mg, 0.5 mmol) in 10 mL of EtOH was added H₂O (0.9 mL), reduced iron powder (448 mg, 8 mmol) and 14 drops of concentrated HCl (12 M). The mixture was stirred under reflux for 4.5 h. After cooling, the mixture was extracted with ethyl acetate. The combined organic layer was washed with water, saturated sodium bicarbonate solution and brine, and then dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel, and eluted with petroleum ether-ethyl acetate (28:1, v/v) to afford DAMBA as white powder (91.5 mg, 0.25 mmol). Yield 50%, m.p. 118.5~119.5 ℃. Anal. Calcd. (%) for C₁₈H₂₄BrNO₂: C, 59.02; H, 6.60; N, 3.82. Found (%): C, 59.11; H, 6.65; N, 3.84. FT-IR (KBr): ν_max 3469, 3374, 2990, 2942, 2917, 2867, 1715, 1617, 1490, 1432, 1411, 1249, 1175, 1134, 1112, 1080, 1016, 976, 873 cm^-1. ¹H NMR (CDCl₃, 600 MHz): δ 7.24 (s, 1H), 6.45 (s, 1H), 3.86 (s, 2H), 3.66 (s, 3H), 2.76~2.74 (m, 2H), 2.20 (m, 1H), 2.15 (m, 1H), 1.80~1.70 (m, 4H), 1.64 (m, 1H), 1.48~1.36 (m, 2H), 1.25 (s, 3H), 1.17 (s, 3H). ¹³C NMR (CDCl₃, 151 MHz): δ 179.14, 141.89, 141.49, 135.60, 128.38, 115.77, 107.46, 52.08, 47.65, 45.00, 38.25, 36.77, 36.76, 29.61, 25.33, 21.61, 18.63, 16.58. MALDI-TOF MS (mass m/z): 365.0972 [M]⁺.

  Scheme 1

  

  Scheme 1.  Syntheses of DAMBA-Fc and DAA-Fc: (a) Iron powder, EtOH, H₂O, HCl, reflux, 4.5 h; (b) Fc-CHO, EtOH, reflux, 3 h; (c) Fc-CHO, pyrrolidine, DCM, inert atmosphere, r.t., overnight

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  Under an inert atmosphere, DAMBA (43.9 mg, 0.12 mmol) and Fc-CHO (21.4 mg, 0.1 mmol) were dissolved in 5 mL of anhydrous DCM. One drop of pyrrolidine was subsequently added to the above mixture as the catalyst. The reaction was kept stirring at room temperature overnight. After filtration through a plug of Celite, the solvent was removed under reduced pressure and an orange oily crude product was received. Finally, orange crystals of DAMBA-Fc were obtained by recrystallization from hexane. Yield: 70%, m.p. 156~158 ℃. Anal. Calcd. (%) for C₂₉H₃₂BrFeNO₂: C, 61.94; H, 5.74; N, 2.49. Found (%): C, 62.01; H, 5.78; N, 2.52. FT-IR (KBr): ν_max 2958, 2925, 2854, 1724, 1625, 1460, 1245, 1133, 1107, 1039 cm^-1. ¹H NMR (CDCl₃, 600 MHz): δ 8.18 (s, 1H), 7.44 (s, 1H), 6.58 (s, 1H), 4.82 (t, 2H), 4.48 (t, 2H), 4.26 (s, 5H), 3.68 (s, 3H), 2.87~2.84 (m, 2H), 2.27 (m, 1H), 2.20 (m, 1H), 1.81~1.73 (m, 4H), 1.67 (m, 1H), 1.53~1.43 (m, 2H), 1.28 (s, 3H), 1.22 (s, 3H). ¹³C NMR (CDCl₃, 151 MHz): δ 179.04, 162.39, 149.19, 147.87, 135.50, 128.77, 120.07, 114.42, 80.12, 71.47, 69.59, 69.41, 69.36, 52.11, 47.67, 44.78, 38.11, 37.19, 36.71, 29.64, 25.20, 21.57, 18.59, 16.62. MALDI-TOF MS (mass m/z): 561.0946 [M]⁺.

  2.2.2   Synthesis of DAA-Fc

  DAA-Fc was synthesized from DAA according to the procedures as follows (Scheme 1). A solution of Fc-CHO (21.4 mg, 0.1 mmol) in 1 mL of EtOH was added slowly to a vigorously stirred solution of DAA (40.0 mg, 0.14 mmol) in 1 mL of EtOH. The reaction mixture was refluxed for 3 h. Then the mixture was cooled to room temperature, with solvent removed under reduced pressure. Pure orange needle-like product was obtained by recrystallization from the ethanol solution. Orange block-shaped single crystals were obtained by slow evaporation from the ethanol solution. Yield: 85%, m.p. 102~104 ℃. Anal. Calcd. (%) for C₃₁H₃₉FeN: C, 77.33; H, 8.16; N, 2.91. Found (%): C, 77.40; H, 8.22; N, 2.93. IR (KBr): ν_max 3433, 2956, 2924, 2853, 1644, 1496, 1463, 1380, 1244, 1105, 1039, 1003, 820 cm^-1. ¹H NMR (CDCl₃, 600 MHz): δ 8.06 (s, 1H), 7.19 (d, J = 8.4 Hz, 2H), 6.99 (dd, J = 8.4 Hz, 2H), 6.89 (s, 1H), 4.60 (m, 2H), 4.32 (m, 2H), 4.13 (s, 5H), 3.32~3.26 (m, 2H), 2.94~2.86 (m, 2H), 2.82 (sept, 1H), 2.29 (m, 1H), 1.96 (m, 1H), 1.82~1.73 (m, 2H), 1.68~1.62 (m, 2H), 1.47~1.39 (m, 3H), 1.25 (s, 3H), 1.22 (d, J = 6.6 Hz, 6H), 1.04 (s, 3H). ¹³C NMR (CDCl₃, 151 MHz): δ 160.53, 147.70, 145.52, 135.10, 126.96, 124.40, 123.87, 81.61, 73.97, 70.20, 70.11, 68.99, 68.61, 68.21, 46.20, 38.69, 37.99, 37.75, 37.01, 33.57, 30.46, 25.58, 24.15, 24.12, 19.51, 19.08, 19.05. MALDI-TOF MS (mass m/z): 481.2415 [M]⁺.

  2.3 X-ray structure determination

  An orange single crystal of DAA-Fc (0.20mm × 0.18mm × 0.15mm) was selected for X-ray diffraction analysis. The data were collected on a Bruker D8 VENTURE PHOTON 100 diffractometer equipped with a graphite-monochromatic MoKα radiation (0.71073 Å) by using an ω-2θ scan mode in the range of 2.42 < θ < 26.00° (–13≤h≤9, –9≤k≤9, –40≤l≤40) at 296(2) K. A total of 21776 reflections were collected, of which 10352 were independent (R_int = 0.0589) and 5645 were observed with I > 2σ(I). The structure was solved by direct methods with SHELXT^[29] and refined by full-matrix least-squares method on F² with SHELXL^[30]. All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms were located by geometric calculations and refined by using a riding mode. The final refinement gave R = 0.0566, wR = 0.0701 (w = 1/[σ²(F_o²) + (0.0144P)²], where P = (F_o² + 2F_c²)/3), S = 1.034, (∆/σ)_max = 0.000, (∆ρ)_max = 0.560 and (∆ρ)_min = –0.166 e/ų. The selected bond distances and bond angles are listed in Table 1.

  Table 1

  

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (°) of DAA-Fc

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  Bond	Dist.		Bond	Dist.
  N(1)–C(26)	1.244(9)		N(2)–C(17)	1.276(8)
  N(1)–C(30)	1.442(8)		N(2)–C(35)	1.450(7)
  C(1)–C(37)	1.53(1)		C(25)–C(24)	1.531(8)
  C(5)–C(7)	1.41(1)		C(4)–C(3)	1.43(1)
  C(5)–C(26)	1.441(9)		C(4)–C(17)	1.449(9)
  C(23)–C(32)	1.560(8)		C(29)–C(19)	1.544(8)
  C(30)–C(37)	1.540(9)		C(35)–C(24)	1.549(9)
  Angle	(°)		Angle	(°)
  C(7)–C(5)–C(28)	105.6(5)		C(3)–C(4)–C(9)	107.6(6)
  C(5)–C(26)–N(1)	123.2(6)		C(4)–C(17)–N(2)	122.7(5)
  C(26)–N(1)–C(30)	119.9(5)		C(17)–N(2)–C(35)	116.7(5)
  C(32)–C(23)–C(43)	109.0(5)		C(19)–C(29)–C(16)	107.7(5)
  C(37)–C(30)–N(1)	111.3(5)		C(24)–C(35)–N(2)	112.9(5)
  C(37)–C(1)–C(42)	113.9(5)		C(24)–C(25)–C(31)	113.3(5)
  C(23)–C(32)–C(53)	109.7(5)		C(29)–C(19)–C(27)	109.4(5)
  N(1)–C(30)–C(37)–C(32)	–174.7(5)		N(2)–C(35)–C(24)–C(19)	–165.3(4)
  C(5)–C(26)–N(1)–C(30)	–176.3(6)		C(4)–C(17)–N(2)–C(35)	–178.1(5)
  C(7)–C(5)–C(26)–N(1)	165.1(7)		C(3)–C(4)–C(17)–N(2)	–164.4(6)
  C(37)–C(30)–N(1)–C(26)	119.7(6)		C(24)–C(35)–N(2)–C(17)	120.7(5)

  3. RESULTS AND DISCUSSION

  3.1 FT-IR spectroscopy

  The FT-IR spectra of two title compounds exhibit strong to medium absorptions around 2960~2850 cm^-1 corresponding to the -C–H stretching of sp³ carbon atoms. The absorption bands around 1580, 1500 and 1460 cm^-1 are due to the benzene skeleton vibration and the absorption bands around 1105 and 1000 cm^-1 are attributed to the C=C stretching vibration of cyclopentadiene (Cp) ring. Besides, the strong vibration bands at 1625 cm^-1 (DAMBA-Fc) and 1644 cm^-1 (DAA-Fc) indicate the formation of -HC=N- as Schiff bases. In addition, the strong absorption of DAA-Fc at 1724 cm^-1 is due to the C=O stretching vibration of the methyl ester moiety.

  3.2 NMR spectroscopy

  In ¹H NMR spectrum of DAMBA-Fc, the proton of the imine group can be found as a singlet at δ 8.18 ppm. The protons of the aromatic ring appear as two singlets at δ 7.44 and 6.58 ppm. Besides, the protons of the substituted Cp ring appear as two triplets, integrating for two protons, at 4.82 and 4.48 ppm and the protons of the non-substituted Cp ring appear as a singlet with a shift of δ 4.26 ppm. Moreover, the protons of the methoxyl group appear as a singlet at δ 3.68 ppm and the methyl protons as two singlets at δ 1.28 and 1.22 ppm, respectively. Similarly, in ¹H NMR spectrum of DAA-Fc, a singlet at δ 8.06 ppm can be attributed to the imine group. A doublet at δ 7.19 ppm, a double doublet at δ 6.99 ppm and a singlet at δ 6.89 ppm can be assigned to the aromatic protons at C(49), C(57) and C(36), respectively. The two multiplets at δ 4.60 and 4.32 ppm, and a singlet at δ 4.13 ppm can be attributed to the substituted Cp protons at C(7, 28), C(8, 13) and unsubstituted Cp protons at C(6, 12, 15, 21 and 34), respectively. Two singlets at δ 1.25 and 1.04 ppm are cased by the methyl protons at C(47) and C(45), respectively. Moreover, there is a doublet at δ 1.22 ppm, corresponding to the two methyl protons of the isopropyl group (C(59) and C(61)), together with a septet at δ 2.82 ppm derived from the CH proton. The ¹³C NMR spectrum of DAMBA-Fc exhibits 24 well resolved resonances. Among them, the carbonyl (C=O) carbon appears at δ 179.04 ppm, while the carbon signal on the imine group is observed at δ 162.39 ppm. Six peaks at δ 149.19, 147.87, 135.50, 128.77, 120.07 and 114.42 ppm can be attributed to the carbons of benzene ring. Besides, the carbon signals on the Cp rings are observed at δ 80.12, 71.47, 69.59, 69.41 and 69.36 ppm. Moreover, the methoxyl carbon on the ester group appears at δ 52.11 ppm. The ¹³C NMR spectrum of DAA-Fc exhibits 27 well resolved resonances. Among them, the peak at δ 160.53 ppm is confirmed to be the signal of C(26) on the imine group. Six peaks at δ 147.70, 145.52, 135.10, 126.96, 124.40 and 123.87 ppm can be attributed to the carbons of benzene ring, and the carbon signals on the Cp rings are observed at δ 81.61, 70.20, 70.11, 68.99, 68.61 and 68.21 ppm. In addition, the peak at δ 73.97 ppm results from the signal of C(30) on the methylene group. The assignments of the signals in the ¹H and ¹³C NMR spectra of DAMBA-Fc and DAA-Fc are in good accordance with their structures.

  3.3 Crystal structure description

  DAA-Fc crystallizes in the monoclinic space group P2₁ and the structure with corresponding atomic numbering scheme is shown in Fig. 1. Two crystallographically independent molecules (molecules Ⅰ and Ⅱ) with variable conformations co-exist in the asymmetric unit. Distinctions can be observed among the bond lengths, bond angles, and torsion angles of the two molecules (Table 1), indicating a deviation between their conformations. Each molecule contains two chair-conformed cyclohexane rings (A/B and A'/B'), one phenyl ring (C and C'), and two Cp rings. As shown in Fig. 1, the Fc group in molecule Ⅰ is inward while that in molecule Ⅱ is outward when placing dehydroabietyl group in the same position (keeping two methyl groups of cyclohexane upward). With respect to molecule Ⅰ, the cyclohexane fragment A has a classical chair conformation, and the aromatic ring C is planar, while ring B adopts a half-chair conformation due to the fusion with the phenyl ring. Two methyl groups (C(45) and C(47)) attached to the bis cyclohexane rings exist in the axial positions in molecule Ⅰ, as well as those in mlecule Ⅱ, because the larger Fc group should sit on the more stabilized equatorial position. Different from the staggered conformation of Fc unit in some Fc-containing compounds^[31-33], the Fc unit in DAA-Fc displays a conformation close to eclipse, which may be due to the influence of the adjacent imine and dehydroabietyl groups. The bond length of C(5)–C(26) (1.441(9) Å) is shorter than that of C(37)–C(30) (1.540(9) Å) because C(26) has an aromatic conjugation with the Fc group. Similar phenomena could be found in molecule Ⅱ. The bond length of C–N in molecule Ⅰ is close to that in molecule Ⅱ, with length of the former to be 1.442(8) (C(30)–N(1)) and the latter being 1.450(7) (C(35)–N(2)). In addition, bond lengths of C(26)–N(1) and C(17)–N(2) are close to each other, found as 1.244(9) and 1.276(8) Å, respectively. At the same time, C(5) and C(30) (C(4)) and C(35)) are on different sides of the C=N bond, which indicates that the compound is of trans configuration. Furthermore, the angles of C(26)–N(1)–C(30) and C(17)–N(2)–C(35) are similar to each other, shown as 119.9(5) and 116.7(5)°, respectively. With regard to their chirality, both molecules have three chiral centers that are derived from the natural diterpene dehydroabietylamine. Their absolute configurations are remained as 23S, 32R, 37R, and 29S, 19R, 24R for molecules Ⅰ and Ⅱ, respectively.

  Figure 1

  

  Figure 1.  Molecular diagram of DAA-Fc with atomic labeling scheme

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  3.4 Electrochemical properties

  The electrochemical properties of Schiff bases DAMBA-Fc and DAA-Fc were investigated using cyclic voltammogram (CV) and differential pulse voltammogram (DPV) techniques. The CV and DPV spectra are shown in Fig. 2. CV results show that both Schiff bases exhibit only one pair of reversible one-electron redox peaks, which can be attributed to the redox process of Fc/Fc⁺ couples in compounds, and the potentials of their anodic and cathodic peaks are as follows: E_pa = 0.288, E_pc = 0.199 V (DAMBA-Fc) and E_pa = 0.145, E_pc = 0.029 V (DAA-Fc) versus Fc/Fc⁺ (Fig. 2A). Moreover, only one symmetrical peak can be observed in the DPV curve of each Schiff base with the oxidation potentials of DAMBA-Fc as 0.224 V and DAA-Fc as 0.080 V (Fig. 2B), which further proves that the redox activity of both Schiff bases is a one-electron reversible redox process. Compared to the oxidation potential of Fc-CHO at around 0.308 V in its DPV curve, the oxidation potentials of both DAMBA-Fc and DAA-Fc shift negatively with circa 0.084 and 0.228 V, respectively, due to the introduction of electron-donating groups of both Schiff-bases. The results show that DAMBA-Fc and DAA-Fc have higher oxidation ability than Fc-CHO. Interestingly, DAA-Fc presents a much lower oxidation potential compared to that of DAMBA-Fc. Such big difference might be derived from the phenyl ring attached to the imine group in DAMBA-Fc, leading to a larger conjugation compared to that in DAA-Fc, hence making it more difficult to be oxidized. All in all, the synthetic compounds DAMBA-Fc and DAA-Fc have good redox performances, which might be potentially used as natural product-based electrochemical sensors^{[21, 22, 34]}.

  Figure 2

  

  Figure 2.  (A) CV and (B) DPV spectra of Fc-CHO, DAMBA-Fc and DAA-Fc recorded in a 0.10 M CH₂Cl₂ solution of electrolyte [n-Bu₄N][PF₆]. All potential values are referenced to Fc/Fc⁺

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  4. CONCLUSION

  In summary, the title compounds DAMBA-Fc and DAA-Fc were synthesized from dehydroabietic acid via using different synthetic methods. Their structures were clearly determined by the use of spectroscopic methods. The crystal structure of DAA-Fc was characterized by single-crystal X-ray diffraction. Two independent molecules with distinct conformations are present in the asymmetric unit of DAA-Fc, while their chiral properties still keep identical. Furthermore, electrochemical properties of the title compounds were examined by cyclic and differential pulse voltammogram techniques, showing that the dehydroabietic acid-derived Schiff bases have good redox activities. Because of the introduction of electron-donating groups, the oxidation potentials of both DAMBA-Fc and DAA-Fc were lower than that of the starting material Fc-CHO, indicating that the oxidation capacities of the two title Schiff bases were higher than that of Fc-CHO. Moreover, the oxidation potential of DAMBA-Fc is much higher than that of DAA-Fc, which may be due to the aromatic ring attached to the imine group in DAMBA-Fc, leading to a larger conjugation compared to that in DAA-Fc, hence making it more difficult to be oxidized. Therefore, DAA-Fc might be more suitable to be a potential electrochemical sensor in comparison to DAMBA-Fc.

  
  
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  Scheme 1  Syntheses of DAMBA-Fc and DAA-Fc: (a) Iron powder, EtOH, H₂O, HCl, reflux, 4.5 h; (b) Fc-CHO, EtOH, reflux, 3 h; (c) Fc-CHO, pyrrolidine, DCM, inert atmosphere, r.t., overnight

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  Figure 1  Molecular diagram of DAA-Fc with atomic labeling scheme

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  Figure 2  (A) CV and (B) DPV spectra of Fc-CHO, DAMBA-Fc and DAA-Fc recorded in a 0.10 M CH₂Cl₂ solution of electrolyte [n-Bu₄N][PF₆]. All potential values are referenced to Fc/Fc⁺

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  Table 1.  Selected Bond Lengths (Å) and Bond Angles (°) of DAA-Fc

  Bond	Dist.		Bond	Dist.
  N(1)–C(26)	1.244(9)		N(2)–C(17)	1.276(8)
  N(1)–C(30)	1.442(8)		N(2)–C(35)	1.450(7)
  C(1)–C(37)	1.53(1)		C(25)–C(24)	1.531(8)
  C(5)–C(7)	1.41(1)		C(4)–C(3)	1.43(1)
  C(5)–C(26)	1.441(9)		C(4)–C(17)	1.449(9)
  C(23)–C(32)	1.560(8)		C(29)–C(19)	1.544(8)
  C(30)–C(37)	1.540(9)		C(35)–C(24)	1.549(9)
  Angle	(°)		Angle	(°)
  C(7)–C(5)–C(28)	105.6(5)		C(3)–C(4)–C(9)	107.6(6)
  C(5)–C(26)–N(1)	123.2(6)		C(4)–C(17)–N(2)	122.7(5)
  C(26)–N(1)–C(30)	119.9(5)		C(17)–N(2)–C(35)	116.7(5)
  C(32)–C(23)–C(43)	109.0(5)		C(19)–C(29)–C(16)	107.7(5)
  C(37)–C(30)–N(1)	111.3(5)		C(24)–C(35)–N(2)	112.9(5)
  C(37)–C(1)–C(42)	113.9(5)		C(24)–C(25)–C(31)	113.3(5)
  C(23)–C(32)–C(53)	109.7(5)		C(29)–C(19)–C(27)	109.4(5)
  N(1)–C(30)–C(37)–C(32)	–174.7(5)		N(2)–C(35)–C(24)–C(19)	–165.3(4)
  C(5)–C(26)–N(1)–C(30)	–176.3(6)		C(4)–C(17)–N(2)–C(35)	–178.1(5)
  C(7)–C(5)–C(26)–N(1)	165.1(7)		C(3)–C(4)–C(17)–N(2)	–164.4(6)
  C(37)–C(30)–N(1)–C(26)	119.7(6)		C(24)–C(35)–N(2)–C(17)	120.7(5)

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