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organic compounds
(Z)-1-(2-Hydroxyethyl)-4-(2-methoxybenzylidene)-2-methyl-1H-imidazol-5(4H)-one
aDepartment of Chemistry, Southern University, Baton Rouge, LA 70813, USA, and bDepartment of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804, USA
*Correspondence e-mail: ffroncz@lsu.edu
In the title compound, C14H16N2O3, an analog of the chromophore in green fluorescent protein, the methoxyphenyl substituent and the imidazole N adopt a Z conformation with respect to the C=C bond. Aside from the hydroxyethyl group, the molecule is approximately planar, with the five- and six-membered ring planes forming a dihedral angle of 9.3 (1)°. An intramolecular C—H⋯N contact occurs. In the crystal, O—H⋯N hydrogen bonds link the molecules, forming chains along the b-axis direction. C—H⋯O hydrogen bonds are also observed.
Related literature
For background to green fluorescent protein, see: Shimomura et al. (1962); Shimomura (2009
); Remington (2006
); Tsien (1998
); Chalfie et al. (1994
); Prasher et al. (1992
). For the synthesis, see: Yampolsky et al. (2005
); Bailly et al.(2004
); Wenge & Wagenknecht (2011
). For related structures, see: Naumov et al. (2010
); Bhattacharjya et al. (2005
); Oshimi et al. (2002
); Dong et al. (2009
). For analysis, see: Hooft et al. (2008
).
Experimental
Crystal data
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|
Data collection: APEX2 (Bruker, 2006); cell SAINT (Bruker, 2006
); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012
); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008
).
Supporting information
10.1107/S1600536813007770/sj5304sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536813007770/sj5304Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536813007770/sj5304Isup3.cml
A mixture of o-anisaldehyde (6.95 g, 50.0 mmol), N-acetylglycine (5.97 g, 50.5 mmol) and anhydrous sodium acetate (4.35 g, 52.5 mmol) were dissolved in 20 ml acetic anhydride. The mixture was stirred at 100° C for 6 h. Upon completion, the reaction mixture was cooled to room temperature. After the addition of 10 ml ice-cold water, the resulting precipitate was collected by gravity filtration. The filtrand was then washed three times with ice-cold water and dried in vacuum, yielding (1) as a yellow powder (8.41 g, 64.7%). Title compound (2) was synthesized by reacting (1) with ethanolamine in 2-propanol. To a suspension of compound (1) (3.30 g, 15.2 mmol) in dried 2-propanol (30 ml), ethanolamine (1.14 ml, 18.8 mmol) was added gradually. The reaction mixture was refluxed for 8 h. The solvent was then removed under vacuo. The crude product was recrystallized from a n-butanol/diethyl ether (1/1, v/v) mixture. Yellow crystals of the title compound (2) were obtained in a yield of 2.77 g (58%). The sample crystal was grown by evaporation from methanol.
FT—IR Characterization (cm-1): 3237, 2944, 1711, 1635, 1423, 1256
NMR Characterization: 1H NMR (400 MHz, CD3Cl): δ 2.39 (s, 3 H, CH3C), 3.74 (t, J = 5.9 Hz, 2H, CH2), 3.81 (t, J=5.9 Hz, 2H, CH2),3.89 (s, 3 H, CH3O), 6.89 (m, 1 H, ArH), 7.02(m, 1 H, ArH), 7.35 (m, 1H, ArH), 7.67 (s, 1 H, HC═C), 8.68 (m, 1 H, ArH); 13C NMR (100 MHz, CD3Cl): δ = 15.9(CH3C), 43.7 (CH2), 55.6(CH3O), 62.0 (CH2), 110.7 (ArCH), 120.9 (ArCH), 122.0 (HC═C),123.1 (ArCC), 131.8 (ArCH), 132.9 (ArCH), 137.7 (HC═C), 159.2(C—O), 162.3 (C═N), 171.3 (C═O).
H atoms on C were located from difference maps, but were placed in idealized positions with C—H distance 0.95 - 0.99 Å, depending on atom type. A torsional parameter was refined for each methyl group. Coordinates for the hydroxy H atom were refined. Uiso for H were assigned as 1.2 times Ueq of the attached atoms (1.5 for methyl and OH).
of the Flack (1983) parameter was inconclusive; however, analysis of the Bijvoet pairs by the Hooft et al. (2008) method yielded a P2(true) value of 1.000. Although the molecule is not inherently chiral, we consider the reported coordinates to likely represent the correct of the crystal studied, and the pairs were kept separate in the refinement.Data collection: APEX2 (Bruker, 2006); cell
SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008). ![]() | Fig. 1. Scheme showing the synthesis. |
![]() | Fig. 2. Ellipsoids at the 50% level, with H atoms having arbitrary radius. |
C14H16N2O3 | F(000) = 276 |
Mr = 260.29 | Dx = 1.350 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 6251 reflections |
a = 9.2188 (5) Å | θ = 3.2–37.7° |
b = 7.2767 (4) Å | µ = 0.10 mm−1 |
c = 9.5620 (5) Å | T = 90 K |
β = 93.625 (6)° | Needle, yellow |
V = 640.16 (6) Å3 | 0.35 × 0.25 × 0.17 mm |
Z = 2 |
Bruker Kappa APEXII DUO CCD diffractometer | 4943 independent reflections |
Radiation source: fine-focus sealed tube | 4720 reflections with I > 2σ(I) |
TRIUMPH curved graphite monochromator | Rint = 0.017 |
ϕ and ω scans | θmax = 37.8°, θmin = 3.2° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2004) | h = −15→13 |
Tmin = 0.967, Tmax = 0.984 | k = −8→12 |
9385 measured reflections | l = −15→15 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.032 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.087 | w = 1/[σ2(Fo2) + (0.0603P)2 + 0.0209P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
4943 reflections | Δρmax = 0.42 e Å−3 |
177 parameters | Δρmin = −0.24 e Å−3 |
1 restraint | Absolute structure: Flack (1983), 1605 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.9 (5) |
C14H16N2O3 | V = 640.16 (6) Å3 |
Mr = 260.29 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 9.2188 (5) Å | µ = 0.10 mm−1 |
b = 7.2767 (4) Å | T = 90 K |
c = 9.5620 (5) Å | 0.35 × 0.25 × 0.17 mm |
β = 93.625 (6)° |
Bruker Kappa APEXII DUO CCD diffractometer | 4943 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2004) | 4720 reflections with I > 2σ(I) |
Tmin = 0.967, Tmax = 0.984 | Rint = 0.017 |
9385 measured reflections |
R[F2 > 2σ(F2)] = 0.032 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.087 | Δρmax = 0.42 e Å−3 |
S = 1.06 | Δρmin = −0.24 e Å−3 |
4943 reflections | Absolute structure: Flack (1983), 1605 Friedel pairs |
177 parameters | Absolute structure parameter: −0.9 (5) |
1 restraint |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.46857 (7) | 0.27870 (9) | 0.59877 (7) | 0.01987 (12) | |
O2 | 0.52843 (7) | 0.87448 (9) | 0.79824 (7) | 0.01835 (11) | |
O3 | 0.11188 (6) | 0.14749 (9) | 0.32174 (6) | 0.01679 (11) | |
H3O | 0.0433 (16) | 0.064 (2) | 0.3128 (15) | 0.025* | |
N1 | 0.23432 (7) | 0.16329 (9) | 0.60614 (7) | 0.01255 (10) | |
N2 | 0.12395 (7) | 0.39039 (9) | 0.72030 (7) | 0.01344 (11) | |
C1 | 0.34363 (8) | 0.29285 (10) | 0.63215 (8) | 0.01374 (12) | |
C2 | 0.10888 (8) | 0.22969 (11) | 0.65921 (7) | 0.01237 (11) | |
C3 | 0.26991 (8) | 0.44057 (10) | 0.70824 (8) | 0.01307 (12) | |
C4 | 0.25234 (8) | 0.00285 (10) | 0.51780 (8) | 0.01355 (12) | |
H4A | 0.1748 | −0.0877 | 0.5335 | 0.016* | |
H4B | 0.3473 | −0.0558 | 0.5431 | 0.016* | |
C5 | 0.24500 (8) | 0.05885 (12) | 0.36415 (8) | 0.01478 (12) | |
H5A | 0.3268 | 0.1428 | 0.3481 | 0.018* | |
H5B | 0.2563 | −0.0519 | 0.3057 | 0.018* | |
C6 | −0.02821 (9) | 0.12268 (11) | 0.64852 (9) | 0.01714 (13) | |
H6A | −0.1019 | 0.1860 | 0.7002 | 0.026* | |
H6B | −0.0108 | 0.0001 | 0.6885 | 0.026* | |
H6C | −0.0626 | 0.1112 | 0.5498 | 0.026* | |
C7 | 0.34421 (8) | 0.59176 (10) | 0.75311 (8) | 0.01367 (12) | |
H7 | 0.4419 | 0.5965 | 0.7272 | 0.016* | |
C8 | 0.29964 (8) | 0.74799 (10) | 0.83426 (7) | 0.01242 (11) | |
C9 | 0.16563 (8) | 0.75856 (11) | 0.89605 (8) | 0.01475 (12) | |
H9 | 0.0969 | 0.6622 | 0.8807 | 0.018* | |
C10 | 0.13176 (9) | 0.90681 (13) | 0.97897 (8) | 0.01816 (14) | |
H10 | 0.0408 | 0.9115 | 1.0203 | 0.022* | |
C11 | 0.23173 (9) | 1.04896 (12) | 1.00136 (8) | 0.01849 (14) | |
H11 | 0.2081 | 1.1511 | 1.0575 | 0.022* | |
C12 | 0.36595 (9) | 1.04289 (11) | 0.94234 (8) | 0.01678 (13) | |
H12 | 0.4338 | 1.1400 | 0.9584 | 0.020* | |
C13 | 0.39992 (8) | 0.89311 (10) | 0.85941 (7) | 0.01325 (11) | |
C14 | 0.64199 (10) | 1.00233 (13) | 0.83403 (11) | 0.02252 (16) | |
H14A | 0.6138 | 1.1243 | 0.7984 | 0.034* | |
H14B | 0.7312 | 0.9629 | 0.7921 | 0.034* | |
H14C | 0.6590 | 1.0076 | 0.9362 | 0.034* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0123 (2) | 0.0188 (3) | 0.0289 (3) | −0.0010 (2) | 0.0046 (2) | −0.0056 (2) |
O2 | 0.0164 (2) | 0.0172 (3) | 0.0220 (2) | −0.0070 (2) | 0.00527 (19) | −0.0056 (2) |
O3 | 0.0147 (2) | 0.0152 (2) | 0.0201 (2) | 0.00069 (19) | −0.00168 (18) | 0.0018 (2) |
N1 | 0.0115 (2) | 0.0103 (2) | 0.0159 (2) | −0.00049 (19) | 0.00164 (18) | −0.0022 (2) |
N2 | 0.0120 (2) | 0.0111 (2) | 0.0174 (2) | −0.00118 (19) | 0.00251 (19) | −0.0013 (2) |
C1 | 0.0126 (3) | 0.0119 (3) | 0.0168 (3) | −0.0009 (2) | 0.0014 (2) | −0.0022 (2) |
C2 | 0.0119 (3) | 0.0103 (2) | 0.0150 (3) | −0.0010 (2) | 0.0021 (2) | 0.0005 (2) |
C3 | 0.0120 (3) | 0.0109 (3) | 0.0164 (3) | −0.0007 (2) | 0.0021 (2) | −0.0018 (2) |
C4 | 0.0156 (3) | 0.0096 (3) | 0.0155 (3) | 0.0011 (2) | 0.0008 (2) | −0.0015 (2) |
C5 | 0.0141 (3) | 0.0154 (3) | 0.0149 (3) | 0.0009 (2) | 0.0013 (2) | −0.0004 (2) |
C6 | 0.0132 (3) | 0.0135 (3) | 0.0250 (3) | −0.0035 (2) | 0.0034 (2) | −0.0009 (3) |
C7 | 0.0129 (3) | 0.0116 (3) | 0.0167 (3) | −0.0018 (2) | 0.0020 (2) | −0.0026 (2) |
C8 | 0.0134 (3) | 0.0109 (3) | 0.0129 (2) | −0.0003 (2) | 0.0002 (2) | −0.0008 (2) |
C9 | 0.0132 (3) | 0.0157 (3) | 0.0154 (3) | 0.0001 (2) | 0.0012 (2) | −0.0022 (2) |
C10 | 0.0176 (3) | 0.0191 (3) | 0.0179 (3) | 0.0020 (3) | 0.0029 (2) | −0.0041 (3) |
C11 | 0.0224 (3) | 0.0162 (3) | 0.0169 (3) | 0.0018 (3) | 0.0012 (2) | −0.0048 (3) |
C12 | 0.0207 (3) | 0.0132 (3) | 0.0162 (3) | −0.0015 (3) | 0.0000 (2) | −0.0028 (2) |
C13 | 0.0149 (3) | 0.0117 (3) | 0.0132 (2) | −0.0019 (2) | 0.0009 (2) | −0.0006 (2) |
C14 | 0.0187 (3) | 0.0176 (3) | 0.0313 (4) | −0.0080 (3) | 0.0022 (3) | −0.0031 (3) |
O1—C1 | 1.2188 (9) | C6—H6A | 0.9800 |
O2—C13 | 1.3608 (9) | C6—H6B | 0.9800 |
O2—C14 | 1.4259 (10) | C6—H6C | 0.9800 |
O3—C5 | 1.4225 (10) | C7—C8 | 1.4504 (10) |
O3—H3O | 0.879 (16) | C7—H7 | 0.9500 |
N1—C2 | 1.3794 (9) | C8—C9 | 1.4048 (10) |
N1—C1 | 1.3908 (10) | C8—C13 | 1.4141 (10) |
N1—C4 | 1.4566 (10) | C9—C10 | 1.3861 (11) |
N2—C2 | 1.3105 (10) | C9—H9 | 0.9500 |
N2—C3 | 1.4061 (10) | C10—C11 | 1.3929 (12) |
C1—C3 | 1.4863 (10) | C10—H10 | 0.9500 |
C2—C6 | 1.4825 (11) | C11—C12 | 1.3928 (12) |
C3—C7 | 1.3515 (11) | C11—H11 | 0.9500 |
C4—C5 | 1.5221 (11) | C12—C13 | 1.3950 (11) |
C4—H4A | 0.9900 | C12—H12 | 0.9500 |
C4—H4B | 0.9900 | C14—H14A | 0.9800 |
C5—H5A | 0.9900 | C14—H14B | 0.9800 |
C5—H5B | 0.9900 | C14—H14C | 0.9800 |
C13—O2—C14 | 118.54 (7) | C2—C6—H6C | 109.5 |
C5—O3—H3O | 108.3 (10) | H6A—C6—H6C | 109.5 |
C2—N1—C1 | 108.16 (6) | H6B—C6—H6C | 109.5 |
C2—N1—C4 | 128.54 (6) | C3—C7—C8 | 130.76 (7) |
C1—N1—C4 | 122.62 (6) | C3—C7—H7 | 114.6 |
C2—N2—C3 | 105.67 (6) | C8—C7—H7 | 114.6 |
O1—C1—N1 | 125.59 (7) | C9—C8—C13 | 118.06 (7) |
O1—C1—C3 | 131.16 (7) | C9—C8—C7 | 123.67 (7) |
N1—C1—C3 | 103.25 (6) | C13—C8—C7 | 118.17 (6) |
N2—C2—N1 | 114.13 (6) | C10—C9—C8 | 121.27 (7) |
N2—C2—C6 | 124.42 (7) | C10—C9—H9 | 119.4 |
N1—C2—C6 | 121.44 (7) | C8—C9—H9 | 119.4 |
C7—C3—N2 | 130.83 (7) | C9—C10—C11 | 119.67 (7) |
C7—C3—C1 | 120.39 (7) | C9—C10—H10 | 120.2 |
N2—C3—C1 | 108.78 (6) | C11—C10—H10 | 120.2 |
N1—C4—C5 | 110.21 (6) | C12—C11—C10 | 120.68 (7) |
N1—C4—H4A | 109.6 | C12—C11—H11 | 119.7 |
C5—C4—H4A | 109.6 | C10—C11—H11 | 119.7 |
N1—C4—H4B | 109.6 | C11—C12—C13 | 119.49 (7) |
C5—C4—H4B | 109.6 | C11—C12—H12 | 120.3 |
H4A—C4—H4B | 108.1 | C13—C12—H12 | 120.3 |
O3—C5—C4 | 112.42 (6) | O2—C13—C12 | 123.71 (7) |
O3—C5—H5A | 109.1 | O2—C13—C8 | 115.47 (6) |
C4—C5—H5A | 109.1 | C12—C13—C8 | 120.81 (7) |
O3—C5—H5B | 109.1 | O2—C14—H14A | 109.5 |
C4—C5—H5B | 109.1 | O2—C14—H14B | 109.5 |
H5A—C5—H5B | 107.9 | H14A—C14—H14B | 109.5 |
C2—C6—H6A | 109.5 | O2—C14—H14C | 109.5 |
C2—C6—H6B | 109.5 | H14A—C14—H14C | 109.5 |
H6A—C6—H6B | 109.5 | H14B—C14—H14C | 109.5 |
C2—N1—C1—O1 | −179.73 (8) | N1—C4—C5—O3 | −58.15 (8) |
C4—N1—C1—O1 | −8.46 (12) | N2—C3—C7—C8 | 3.33 (14) |
C2—N1—C1—C3 | 0.98 (8) | C1—C3—C7—C8 | −176.57 (7) |
C4—N1—C1—C3 | 172.26 (6) | C3—C7—C8—C9 | 7.28 (13) |
C3—N2—C2—N1 | 0.45 (8) | C3—C7—C8—C13 | −176.50 (8) |
C3—N2—C2—C6 | 179.24 (7) | C13—C8—C9—C10 | 0.22 (11) |
C1—N1—C2—N2 | −0.96 (9) | C7—C8—C9—C10 | 176.44 (7) |
C4—N1—C2—N2 | −171.57 (7) | C8—C9—C10—C11 | 0.31 (12) |
C1—N1—C2—C6 | −179.80 (7) | C9—C10—C11—C12 | −0.59 (13) |
C4—N1—C2—C6 | 9.60 (11) | C10—C11—C12—C13 | 0.33 (12) |
C2—N2—C3—C7 | −179.70 (8) | C14—O2—C13—C12 | 8.09 (11) |
C2—N2—C3—C1 | 0.21 (8) | C14—O2—C13—C8 | −171.68 (7) |
O1—C1—C3—C7 | −0.05 (13) | C11—C12—C13—O2 | −179.54 (7) |
N1—C1—C3—C7 | 179.18 (7) | C11—C12—C13—C8 | 0.22 (11) |
O1—C1—C3—N2 | −179.97 (9) | C9—C8—C13—O2 | 179.29 (7) |
N1—C1—C3—N2 | −0.74 (8) | C7—C8—C13—O2 | 2.86 (10) |
C2—N1—C4—C5 | 94.61 (9) | C9—C8—C13—C12 | −0.49 (11) |
C1—N1—C4—C5 | −74.77 (9) | C7—C8—C13—C12 | −176.92 (7) |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3O···N2i | 0.879 (16) | 2.001 (16) | 2.8771 (9) | 174.2 (15) |
C4—H4B···O1ii | 0.99 | 2.54 | 3.2993 (10) | 133 |
C9—H9···N2 | 0.95 | 2.52 | 3.1729 (10) | 126 |
C14—H14A···O1iii | 0.98 | 2.52 | 3.3475 (12) | 141 |
Symmetry codes: (i) −x, y−1/2, −z+1; (ii) −x+1, y−1/2, −z+1; (iii) x, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | C14H16N2O3 |
Mr | 260.29 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 90 |
a, b, c (Å) | 9.2188 (5), 7.2767 (4), 9.5620 (5) |
β (°) | 93.625 (6) |
V (Å3) | 640.16 (6) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.35 × 0.25 × 0.17 |
Data collection | |
Diffractometer | Bruker Kappa APEXII DUO CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2004) |
Tmin, Tmax | 0.967, 0.984 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9385, 4943, 4720 |
Rint | 0.017 |
(sin θ/λ)max (Å−1) | 0.862 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.087, 1.06 |
No. of reflections | 4943 |
No. of parameters | 177 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.42, −0.24 |
Absolute structure | Flack (1983), 1605 Friedel pairs |
Absolute structure parameter | −0.9 (5) |
Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 2012).
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3O···N2i | 0.879 (16) | 2.001 (16) | 2.8771 (9) | 174.2 (15) |
C4—H4B···O1ii | 0.99 | 2.54 | 3.2993 (10) | 133 |
C9—H9···N2 | 0.95 | 2.52 | 3.1729 (10) | 126 |
C14—H14A···O1iii | 0.98 | 2.52 | 3.3475 (12) | 141 |
Symmetry codes: (i) −x, y−1/2, −z+1; (ii) −x+1, y−1/2, −z+1; (iii) x, y+1, z. |
Acknowledgements
This research was made possible by a grant supplied by the National Science Foundation's Early CAREER program (Cooperative Agreement DMR-0449886)and by the National Science Foundations HBCU–RISE program (Cooperative Agreement HRD-1036588) at Southern University. The purchase of the NMR was made possible by the National Science Foundation's Major Research Instrument program (Cooperative Agreement CHE-0321591) at Southern University. The purchase of the FTIR at Southern University was made possible by the support from Louisiana Board of Regents (grant No. LEQSF(2005–2007)-ENH-TR-65). We also want to thank the US Department of Education: Title III Part B HBGI program (grant No. P031B040030) at Southern University. Upgrade of the diffractometer at LSU was made possible by grant No. LEQSF(2011–12)-ENH-TR-01, administered by the Louisiana Board of Regents.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The title compound is an analog of the chromophore in green fluorescent protein (GFP). GFP was first identified and separated from the jellyfish Aequorea victoria in the 1960s. Since then, GFP has found broad use in many areas of science and medicine, especially as fluorescent labels for cell biology and biotechnology. (Shimomura et al., 1962; Shimomura, 2009; Remington, 2006; Tsien, 1998; Chalfie et al., 1994) Though the GFP is a protein composed of more than two hundred amino acid residues, its chromophore (p-hydroxybenzylidene-imidazol-5-one) is relatively small. In nature, the GFP chromophore is formed via the sequential cyclization-oxidation-dehydration of the Ser65—Tyr66—Gly67 tripeptide motif. (Prasher et al., 1992)
Preparation of the title compound starts with the Erlenmeyer azlactone synthesis, which involves the condensation of hippuric acid derivatives with aromatic aldehydes (Yampolsky et al., 2005; Bailly et al., 2004), Fig. 1. Further reaction of the resulting azlactone with ethanolamine leads to the formation of the title compound. We report the crystal structure of the compound here, which shows the compound has a Z-configuration. The compound is used as a model compound in our study of E, Z-isomerization of chromophores in fluorescent proteins.
The structure of the molecule is shown in Fig. 2. The Z configuration is evidenced by the torsion angle N2–C3–C7–C8 3.33 (14)° about the central double bond. The hydroxyethyl group is twisted away from coplanarity with the rest of the molecule (C1–N1–C4–C5 torsion angle -74.77 (9)°), but otherwise, the molecule is relatively planar, with the phenyl and imidazole rings forming a dihedral angle of 9.3 (1)°.
The OH group O3 forms a near-linear intermolecular hydrogen bond to the imidazole nitrogen atom N2 (at -x, y-1/2, 1-z), forming chains in the b direction, propagated by the screw axis. Several intermolecular C–H···O hydrogen bonds and an intramolecular C–H···N contact also exist, as given in Table 1.