organic compounds
(RS)-2-Oxo-4-(1-phenylethylamino)-1,2-dihydroquinoline-3-carboxylic acid
aSTC `Institute for Single Crystals', National Academy of Sciences of Ukraine, 60 Lenina avenue, Kharkiv 61001, Ukraine, and bNational University of Pharmacy, 4 Blyukhera avenue, Kharkiv 61002, Ukraine
*Correspondence e-mail: sveta@xray.isc.kharkov.com
The molecular structure of the title compound, C18H16N2O3, does not differ in the crystals of the (I), and the pure (II). In their crystal structures, inversion dimers occur in (I) via N—H⋯O hydrogen bonds and infinite chains in (II) also via N—H⋯O hydrogen bonds.
Related literature
For the S and R enantiomers, see: Ukrainets et al. (2010). For bond lengths in related structures, see: Bürgi & Dunitz (1994).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: CrysAlis PRO (Oxford Diffraction, 2005); cell CrysAlis PRO; data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536811043297/jj2104sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811043297/jj2104Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536811043297/jj2104Isup3.cml
2-Oxo-4-(1-phenylethylamino)-1,2-dihydroquinoline-3-carboxylic acid was synthesized using the published method (Ukrainets et al., 2010). Yield 75%. M.p. 225–227° C.
H1N, H2N and H3O were located from by a Fourier map and refined isotropically. All of the remaining hydrogen atoms were placed in their calculated positions and then refined using the riding model with Atom—H lengths of 0.93Å (CH) or 0.96Å (CH3). Isotropic displacement parameters for these atoms were set to 1.2 (CH) or 1.5 (CH3) times Ueq of the parent atom.
Data collection: CrysAlis PRO (Oxford Diffraction, 2005); cell
CrysAlis PRO (Oxford Diffraction, 2005); data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C18H16N2O3 | F(000) = 648 |
Mr = 308.33 | Dx = 1.393 Mg m−3 |
Monoclinic, P21/n | Melting point = 498–500 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 14.612 (2) Å | Cell parameters from 1534 reflections |
b = 5.9750 (6) Å | θ = 3.0–32.0° |
c = 18.014 (2) Å | µ = 0.10 mm−1 |
β = 110.814 (14)° | T = 293 K |
V = 1470.0 (3) Å3 | Needle, colourless |
Z = 4 | 0.30 × 0.10 × 0.05 mm |
Oxford Diffraction Xcalibur 3 diffractometer | 1174 reflections with I > 2σ(I) |
Radiation source: Enhance (Mo) X-ray Source | Rint = 0.068 |
Graphite monochromator | θmax = 25.0°, θmin = 3.0° |
Detector resolution: 16.1827 pixels mm-1 | h = −17→17 |
ω scans | k = −7→7 |
10943 measured reflections | l = −20→21 |
2541 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.031 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.033 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.66 | w = 1/[σ2(Fo2) + (0.0067P)2] where P = (Fo2 + 2Fc2)/3 |
2541 reflections | (Δ/σ)max = 0.001 |
221 parameters | Δρmax = 0.10 e Å−3 |
0 restraints | Δρmin = −0.10 e Å−3 |
C18H16N2O3 | V = 1470.0 (3) Å3 |
Mr = 308.33 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 14.612 (2) Å | µ = 0.10 mm−1 |
b = 5.9750 (6) Å | T = 293 K |
c = 18.014 (2) Å | 0.30 × 0.10 × 0.05 mm |
β = 110.814 (14)° |
Oxford Diffraction Xcalibur 3 diffractometer | 1174 reflections with I > 2σ(I) |
10943 measured reflections | Rint = 0.068 |
2541 independent reflections |
R[F2 > 2σ(F2)] = 0.031 | 0 restraints |
wR(F2) = 0.033 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.66 | Δρmax = 0.10 e Å−3 |
2541 reflections | Δρmin = −0.10 e Å−3 |
221 parameters |
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 | ||
N1 | 0.54636 (9) | 0.7456 (2) | −0.03766 (8) | 0.0393 (3) | |
H1N | 0.4891 (13) | 0.631 (2) | −0.0545 (9) | 0.116 (7)* | |
N2 | 0.77647 (10) | 1.19200 (19) | 0.02901 (9) | 0.0456 (4) | |
H2N | 0.8164 (9) | 1.153 (2) | 0.0800 (9) | 0.058 (5)* | |
O1 | 0.61318 (7) | 0.55549 (16) | 0.07595 (6) | 0.0498 (3) | |
O2 | 0.84379 (7) | 0.97876 (16) | 0.16236 (6) | 0.0615 (3) | |
O3 | 0.76182 (8) | 0.6926 (2) | 0.18244 (7) | 0.0613 (4) | |
H3O | 0.7056 (15) | 0.610 (3) | 0.1530 (12) | 0.138 (9)* | |
C1 | 0.54064 (10) | 0.9229 (2) | −0.08811 (8) | 0.0350 (4) | |
C2 | 0.45947 (10) | 0.9355 (2) | −0.15744 (9) | 0.0447 (4) | |
H2 | 0.4131 | 0.8214 | −0.1703 | 0.054* | |
C3 | 0.44735 (11) | 1.1146 (2) | −0.20685 (9) | 0.0485 (4) | |
H3 | 0.3921 | 1.1251 | −0.2527 | 0.058* | |
C4 | 0.51788 (11) | 1.2804 (2) | −0.18817 (9) | 0.0490 (4) | |
H4 | 0.5097 | 1.4034 | −0.2216 | 0.059* | |
C5 | 0.59936 (10) | 1.2656 (2) | −0.12129 (9) | 0.0448 (4) | |
H5 | 0.6463 | 1.3781 | −0.1104 | 0.054* | |
C6 | 0.61435 (10) | 1.0856 (2) | −0.06863 (8) | 0.0340 (4) | |
C7 | 0.69759 (10) | 1.0588 (2) | 0.00556 (8) | 0.0344 (4) | |
C8 | 0.69570 (10) | 0.8825 (2) | 0.05766 (9) | 0.0351 (4) | |
C9 | 0.61762 (11) | 0.7222 (2) | 0.03378 (10) | 0.0378 (4) | |
C10 | 0.77197 (12) | 0.8569 (3) | 0.13643 (10) | 0.0472 (4) | |
C11 | 0.80766 (10) | 1.3854 (2) | −0.00571 (9) | 0.0424 (4) | |
H11 | 0.7558 | 1.4987 | −0.0191 | 0.051* | |
C12 | 0.89830 (10) | 1.4790 (2) | 0.05891 (8) | 0.0595 (5) | |
H12C | 0.9503 | 1.3712 | 0.0714 | 0.089* | |
H12B | 0.8833 | 1.5102 | 0.1056 | 0.089* | |
H12A | 0.9183 | 1.6145 | 0.0404 | 0.089* | |
C13 | 0.83092 (10) | 1.3343 (2) | −0.07889 (9) | 0.0379 (4) | |
C14 | 0.81570 (10) | 1.4954 (2) | −0.13665 (10) | 0.0498 (4) | |
H14 | 0.7851 | 1.6288 | −0.1324 | 0.060* | |
C15 | 0.84497 (12) | 1.4625 (3) | −0.20070 (10) | 0.0609 (5) | |
H15 | 0.8341 | 1.5733 | −0.2392 | 0.073* | |
C16 | 0.88995 (12) | 1.2670 (3) | −0.20764 (11) | 0.0664 (5) | |
H16 | 0.9103 | 1.2443 | −0.2504 | 0.080* | |
C17 | 0.90463 (12) | 1.1050 (3) | −0.15065 (12) | 0.0642 (5) | |
H17 | 0.9351 | 0.9718 | −0.1552 | 0.077* | |
C18 | 0.87513 (11) | 1.1362 (2) | −0.08708 (10) | 0.0513 (4) | |
H18 | 0.8849 | 1.0236 | −0.0494 | 0.062* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0343 (8) | 0.0428 (8) | 0.0359 (10) | −0.0088 (7) | 0.0063 (7) | 0.0011 (6) |
N2 | 0.0365 (9) | 0.0539 (9) | 0.0423 (11) | −0.0131 (7) | 0.0091 (8) | 0.0010 (7) |
O1 | 0.0443 (7) | 0.0459 (6) | 0.0516 (8) | −0.0080 (5) | 0.0075 (6) | 0.0116 (6) |
O2 | 0.0469 (8) | 0.0690 (7) | 0.0517 (8) | −0.0163 (6) | −0.0031 (6) | 0.0055 (6) |
O3 | 0.0458 (8) | 0.0709 (8) | 0.0538 (10) | −0.0083 (7) | 0.0011 (7) | 0.0206 (7) |
C1 | 0.0342 (10) | 0.0403 (10) | 0.0311 (11) | −0.0008 (8) | 0.0122 (8) | −0.0026 (8) |
C2 | 0.0367 (11) | 0.0486 (10) | 0.0443 (12) | −0.0072 (7) | 0.0090 (9) | −0.0016 (8) |
C3 | 0.0385 (10) | 0.0665 (11) | 0.0356 (12) | −0.0035 (9) | 0.0071 (8) | 0.0007 (9) |
C4 | 0.0402 (10) | 0.0580 (11) | 0.0468 (13) | 0.0002 (9) | 0.0133 (9) | 0.0142 (8) |
C5 | 0.0330 (10) | 0.0503 (10) | 0.0497 (13) | −0.0089 (8) | 0.0132 (9) | 0.0036 (8) |
C6 | 0.0306 (9) | 0.0414 (10) | 0.0305 (11) | −0.0022 (8) | 0.0113 (8) | −0.0044 (7) |
C7 | 0.0276 (10) | 0.0399 (9) | 0.0373 (11) | −0.0021 (8) | 0.0135 (8) | −0.0065 (8) |
C8 | 0.0259 (9) | 0.0428 (10) | 0.0334 (11) | −0.0028 (7) | 0.0066 (8) | −0.0019 (8) |
C9 | 0.0356 (10) | 0.0367 (10) | 0.0415 (12) | 0.0008 (8) | 0.0143 (9) | −0.0011 (8) |
C10 | 0.0426 (12) | 0.0479 (12) | 0.0490 (13) | −0.0006 (9) | 0.0137 (10) | 0.0017 (9) |
C11 | 0.0357 (10) | 0.0423 (9) | 0.0499 (12) | −0.0100 (8) | 0.0163 (9) | −0.0049 (8) |
C12 | 0.0563 (11) | 0.0621 (11) | 0.0569 (13) | −0.0238 (9) | 0.0161 (9) | −0.0139 (9) |
C13 | 0.0334 (10) | 0.0371 (10) | 0.0440 (12) | −0.0090 (7) | 0.0145 (8) | −0.0046 (8) |
C14 | 0.0458 (11) | 0.0454 (11) | 0.0590 (13) | −0.0042 (7) | 0.0195 (10) | −0.0003 (9) |
C15 | 0.0609 (13) | 0.0689 (13) | 0.0548 (14) | −0.0091 (10) | 0.0230 (10) | 0.0084 (10) |
C16 | 0.0680 (14) | 0.0798 (15) | 0.0593 (14) | −0.0109 (11) | 0.0323 (11) | −0.0136 (11) |
C17 | 0.0672 (13) | 0.0517 (11) | 0.0828 (16) | 0.0006 (9) | 0.0377 (12) | −0.0127 (11) |
C18 | 0.0563 (12) | 0.0433 (11) | 0.0597 (13) | −0.0006 (9) | 0.0273 (10) | 0.0019 (9) |
N1—C9 | 1.3444 (17) | C7—C8 | 1.4177 (16) |
N1—C1 | 1.3788 (16) | C8—C9 | 1.4334 (17) |
N1—H1N | 1.038 (17) | C8—C10 | 1.4679 (18) |
N2—C7 | 1.3395 (15) | C11—C13 | 1.5051 (17) |
N2—C11 | 1.4619 (16) | C11—C12 | 1.5251 (16) |
N2—H2N | 0.926 (14) | C11—H11 | 0.9800 |
O1—C9 | 1.2684 (15) | C12—H12C | 0.9600 |
O2—C10 | 1.2252 (15) | C12—H12B | 0.9600 |
O3—C10 | 1.3268 (17) | C12—H12A | 0.9600 |
O3—H3O | 0.943 (19) | C13—C14 | 1.3760 (16) |
C1—C2 | 1.3854 (16) | C13—C18 | 1.3812 (16) |
C1—C6 | 1.4000 (15) | C14—C15 | 1.3796 (19) |
C2—C3 | 1.3626 (16) | C14—H14 | 0.9300 |
C2—H2 | 0.9300 | C15—C16 | 1.3675 (19) |
C3—C4 | 1.3825 (17) | C15—H15 | 0.9300 |
C3—H3 | 0.9300 | C16—C17 | 1.3712 (19) |
C4—C5 | 1.3629 (19) | C16—H16 | 0.9300 |
C4—H4 | 0.9300 | C17—C18 | 1.3721 (19) |
C5—C6 | 1.3986 (17) | C17—H17 | 0.9300 |
C5—H5 | 0.9300 | C18—H18 | 0.9300 |
C6—C7 | 1.4614 (17) | ||
C9—N1—C1 | 123.76 (14) | O2—C10—O3 | 118.18 (16) |
C9—N1—H1N | 118.7 (9) | O2—C10—C8 | 124.05 (15) |
C1—N1—H1N | 117.3 (8) | O3—C10—C8 | 117.77 (14) |
C7—N2—C11 | 134.34 (14) | N2—C11—C13 | 114.59 (12) |
C7—N2—H2N | 109.4 (8) | N2—C11—C12 | 106.35 (12) |
C11—N2—H2N | 116.2 (8) | C13—C11—C12 | 109.74 (12) |
C10—O3—H3O | 107.6 (12) | N2—C11—H11 | 108.7 |
N1—C1—C2 | 117.90 (14) | C13—C11—H11 | 108.7 |
N1—C1—C6 | 120.48 (14) | C12—C11—H11 | 108.7 |
C2—C1—C6 | 121.61 (14) | C11—C12—H12C | 109.5 |
C3—C2—C1 | 120.16 (14) | C11—C12—H12B | 109.5 |
C3—C2—H2 | 119.9 | H12C—C12—H12B | 109.5 |
C1—C2—H2 | 119.9 | C11—C12—H12A | 109.5 |
C2—C3—C4 | 119.44 (15) | H12C—C12—H12A | 109.5 |
C2—C3—H3 | 120.3 | H12B—C12—H12A | 109.5 |
C4—C3—H3 | 120.3 | C14—C13—C18 | 118.34 (14) |
C5—C4—C3 | 120.65 (14) | C14—C13—C11 | 119.62 (14) |
C5—C4—H4 | 119.7 | C18—C13—C11 | 121.81 (14) |
C3—C4—H4 | 119.7 | C13—C14—C15 | 121.19 (15) |
C4—C5—C6 | 121.79 (14) | C13—C14—H14 | 119.4 |
C4—C5—H5 | 119.1 | C15—C14—H14 | 119.4 |
C6—C5—H5 | 119.1 | C16—C15—C14 | 120.00 (16) |
C5—C6—C1 | 116.28 (13) | C16—C15—H15 | 120.0 |
C5—C6—C7 | 125.69 (14) | C14—C15—H15 | 120.0 |
C1—C6—C7 | 117.98 (13) | C15—C16—C17 | 119.13 (17) |
N2—C7—C8 | 116.72 (13) | C15—C16—H16 | 120.4 |
N2—C7—C6 | 124.51 (14) | C17—C16—H16 | 120.4 |
C8—C7—C6 | 118.77 (13) | C16—C17—C18 | 121.14 (16) |
C7—C8—C9 | 119.89 (14) | C16—C17—H17 | 119.4 |
C7—C8—C10 | 122.05 (14) | C18—C17—H17 | 119.4 |
C9—C8—C10 | 118.06 (14) | C17—C18—C13 | 120.19 (14) |
O1—C9—N1 | 117.89 (13) | C17—C18—H18 | 119.9 |
O1—C9—C8 | 123.34 (15) | C13—C18—H18 | 119.9 |
N1—C9—C8 | 118.75 (15) | ||
C9—N1—C1—C2 | −175.26 (14) | C1—N1—C9—C8 | −3.8 (2) |
C9—N1—C1—C6 | 3.8 (2) | C7—C8—C9—O1 | 177.18 (13) |
N1—C1—C2—C3 | 175.92 (13) | C10—C8—C9—O1 | −2.7 (2) |
C6—C1—C2—C3 | −3.2 (2) | C7—C8—C9—N1 | −1.2 (2) |
C1—C2—C3—C4 | 1.6 (2) | C10—C8—C9—N1 | 178.91 (13) |
C2—C3—C4—C5 | 0.4 (2) | C7—C8—C10—O2 | −2.3 (2) |
C3—C4—C5—C6 | −0.9 (2) | C9—C8—C10—O2 | 177.57 (14) |
C4—C5—C6—C1 | −0.5 (2) | C7—C8—C10—O3 | 177.13 (13) |
C4—C5—C6—C7 | −177.97 (14) | C9—C8—C10—O3 | −3.0 (2) |
N1—C1—C6—C5 | −176.49 (13) | C7—N2—C11—C13 | −67.3 (2) |
C2—C1—C6—C5 | 2.57 (19) | C7—N2—C11—C12 | 171.26 (14) |
N1—C1—C6—C7 | 1.15 (19) | N2—C11—C13—C14 | 149.27 (13) |
C2—C1—C6—C7 | −179.79 (13) | C12—C11—C13—C14 | −91.19 (15) |
C11—N2—C7—C8 | 179.24 (15) | N2—C11—C13—C18 | −36.34 (18) |
C11—N2—C7—C6 | −1.6 (2) | C12—C11—C13—C18 | 83.21 (15) |
C5—C6—C7—N2 | −7.6 (2) | C18—C13—C14—C15 | −1.0 (2) |
C1—C6—C7—N2 | 175.04 (13) | C11—C13—C14—C15 | 173.62 (14) |
C5—C6—C7—C8 | 171.59 (13) | C13—C14—C15—C16 | 0.0 (2) |
C1—C6—C7—C8 | −5.81 (18) | C14—C15—C16—C17 | 0.5 (2) |
N2—C7—C8—C9 | −174.91 (12) | C15—C16—C17—C18 | −0.1 (3) |
C6—C7—C8—C9 | 5.87 (19) | C16—C17—C18—C13 | −0.8 (3) |
N2—C7—C8—C10 | 4.98 (19) | C14—C13—C18—C17 | 1.4 (2) |
C6—C7—C8—C10 | −174.23 (13) | C11—C13—C18—C17 | −173.10 (15) |
C1—N1—C9—O1 | 177.72 (12) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···O1i | 1.038 (17) | 1.794 (17) | 2.8291 (15) | 174.5 (14) |
N2—H2N···O2 | 0.926 (14) | 1.738 (14) | 2.5849 (17) | 150.4 (12) |
O3—H3O···O1 | 0.943 (19) | 1.59 (2) | 2.4712 (15) | 154.1 (18) |
Symmetry code: (i) −x+1, −y+1, −z. |
Experimental details
Crystal data | |
Chemical formula | C18H16N2O3 |
Mr | 308.33 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 293 |
a, b, c (Å) | 14.612 (2), 5.9750 (6), 18.014 (2) |
β (°) | 110.814 (14) |
V (Å3) | 1470.0 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.30 × 0.10 × 0.05 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur 3 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10943, 2541, 1174 |
Rint | 0.068 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.033, 0.66 |
No. of reflections | 2541 |
No. of parameters | 221 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.10, −0.10 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2005), CrysAlis RED (Oxford Diffraction, 2005), SHELXTL (Sheldrick, 2008).
O1—C9 | 1.2684 (15) | C7—C8 | 1.4177 (16) |
O2—C10 | 1.2252 (15) | C8—C9 | 1.4334 (17) |
O3—C10 | 1.3268 (17) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···O1i | 1.038 (17) | 1.794 (17) | 2.8291 (15) | 174.5 (14) |
N2—H2N···O2 | 0.926 (14) | 1.738 (14) | 2.5849 (17) | 150.4 (12) |
O3—H3O···O1 | 0.943 (19) | 1.59 (2) | 2.4712 (15) | 154.1 (18) |
Symmetry code: (i) −x+1, −y+1, −z. |
References
Bürgi, H.-B. & Dunitz, J. D. (1994). Structure Correlation, Vol. 2, pp. 767–784. Weinheim: VCH. Google Scholar
Oxford Diffraction (2005). CrysAlis PRO and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, Oxfordshire, England. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Ukrainets, I. V., Mospanova, E. V., Davidenko, A. A. & Shishkina, S. V. (2010). Khim. Geterotsikl. Soedin. pp. 1690–1701. Google Scholar
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In the title compound, (I), the racemate of 2-oxo-4-(1-phenylethylamino)-1,2- dihydroquinoline-3-carboxylic acid reveals high analgesic activity. Compared to its pure S and R enantiomers, they are completely inactive (Ukrainets et al., 2010). In this paper we compare the molecular and crystal structure of the racemate (I) with a previously studied structure of the pure enantiomer (II). In the title compound (Fig. 1) the formation of two strong N2—H···O2 and O3—H···O1 intramolecular hydrogen bonds (Table 1) contributes to the coplanarity of the heterocycle, carboxyl, carbonyl groups and N2 atom all to be within 0.02 Å. As a result a significant redistribution of the electron density occurs in the quinolone fragment: the O3—C10 and C8—C9 bonds are shortened (Table 1) as compared with their mean values of 1.362 Å and 1.455 Å (Bürgi & Dunitz, 1994). The O1—C9, O2—C10, and C7—C8 bonds are elongated (mean values are 1.210 Å for a Csp2= O bond and 1.418 Å for a Csp2= Csp2 bond). The substituent at the amino group has a sp- conformation. The C6—C7 bond (C11/N2/C7/C6 torsion angle = -1.6 (2)%A) is twisted slghtly allowing the methyl group to be ap- oriented relative to the C7—N2 bond (C7/N2/C11/C12 torsion angle = 171.3 (1)%A). The phenyl substituent is in a -sc-conformation relative to the C7—N2 bond and is twisted toward the N2—C11 bond (C7/N2/C11/C13 and N2/C11/C13/C18 torsion angles = -67.3 (2) %A and 36.3 (2) %A, respectively). The crystal structure of (I), therefore, differs significantly from that of (II). In the pure enantiomer (II) infinite chains (Fig. 2) result from the formation of an N1—H···O2 intermolecular hydrogen bond (Ukrainets et al., 2010). In the racemte, (I), centrosymmetric dimers (Fig. 3) are formed by a N1—H1N···O1 intermolecular hydrogen bond (Table 2). This allows for Cg1—Cg1 π—π stacking interactions to be observed [centroid–centroid distance = 3.894 (1)Åi; i = 1-x, 2-y, -z; Cg1 = N1/C1/C6-C9].