organic compounds
rac-N-(4-Ethoxyphenyl)-3-hydroxybutanamide
aDepartment of Environmental Toxicology, Southern University and A&M College, Baton Rouge, LA 70813, USA, and bDepartment of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
*Correspondence e-mail: rao_uppu@subr.edu
In the title compound, racemic bucetin [systematic name: N-(4-ethoxyphenyl)-3-hydroxybutanamide], C12H17NO3, the molecule is in an extended conformation as illustrated by the C—O—C—C torsion angle [170.14 (15)°] in the ethoxy group and the subsequent C—N—C—C [−177.24 (16)°], N—C—C—C [170.08 (15)°] and C—C—C—C [171.41 (15)°] torsion angles in the butanamide chain. In the crystal, the O—H group donates an intermolecular O—H⋯O hydrogen bond to the amide carbonyl oxygen atom and also accepts an intermolecular N—H⋯O hydrogen bond from an adjacent N—H group. The former forms 12-membered dimeric rings about inversion centers, and the latter form chains in the [001] direction. The overall hydrogen-bonded network is two-dimensional, with no propagation in the [100] direction.
Keywords: bucetin; non-opioid analgesics; crystal structure; hydrogen bonding.
CCDC reference: 2247342
Structure description
N-(4-Ethoxyphenyl)-3-hydrobutanamide, popularly known as bucetin, is an analgesic and antipyric that is similar in structure to phenacetin [N-(4-ethoxyphenyl)acetamide]. Once thought to be a better substitute for phenacetin (Ehrhart et al., 1965; Ehrhart & Ott, 1958), bucetin was introduced into the markets in Germany but was soon withdrawn from use because of renal toxicity and risk of carcinogenesis (Fung et al., 2001; Togei et al., 1987). The renal toxicity of bucetin, renal papillary necrosis, is similar in nature to that induced by phenacetin but is somewhat less pronounced, presumably due to differences in the rates of deacylation by microsomal enzymes leading to the formation of 4-ethoxyaniline (Nohmi et al., 1984). Thus, the renal papillary necrosis by phenacetin and bucetin appears to be a manifestation of the formation of 4-ethoxyaniline and the subsequent inhibitory action(s) of this putative metabolite (or its hydroxylated and/or autooxidation products, N-(4-ethoxyphenyl)hydroxylamine and 1-ethoxy-4-nitrosobenzene) on PGE2 synthesis and a possible reduction of COX-2 expression (Camus et al., 1982; Goodin et al., 2002; Kankuri et al., 2003; Wirth et al., 1982).
Previous studies from our laboratory and elsewhere have shown that celluar oxidants, such as peroxynitrite/peroxynitrous acid and hypochlorite/hypochlorous acid, can constitute an important pathway for non-enzymatic biotransformation of N-(4-hydroxyphenyl)acetamide (Bedner & MacCrehan, 2006; Uppu & Martin, 2004; Whiteman et al., 1996), apocynin (Gernapudi et al., 2009), clozapine (Frimat et al., 1997; Uppu et al., 2005), and certain other xenobiotics (Babu et al., 2012; Ju & Uetrecht, 1998; Rattay & Benndorf, 2021). We believe that the above referenced oxidants may also be involved in the biotransformation of bucetin, leading to the formation of hydroxylated, chlorinated, and nitrated products and thus contribute to the toxicity. To address this and to better understand the mechanisms of toxicity of bucetin and phenacetin and its congeners, we determined the of racemic bucetin.
The molecular structure of the title compound, racemic bucetin, is shown in Fig. 1. The molecule is in an extended conformation as illustrated by torsion angle C4—O1—C11—C12 [170.14 (15)°] in the ethoxy group and torsion angles C1—N1—C7—C8 [−177.24 (16)°], N1—C7—C8—C9 [170.08 (15)°] and C7—C8—C9—C10 [171.41 (15)°] in the butanamide chain. In the arbitrarily chosen asymmetric molecule, atom C9 has an R configuration, but crystal symmetry generates a racemic mixture.
As shown in Fig. 2, the OH group donates an intermolecular hydrogen bond to the amide carbonyl oxygen atom and accepts an intermolecular hydrogen bond from an adjacent N—H group. The donor–acceptor separations for these hydrogen bonds are 2.7268 (17) Å for O—H⋯O(−x + 1, −y + 1, −z + 2) and 2.8611 (19) Å for N—H⋯O(x, −y + , z − ). The former thus forms 12-membered dimeric rings about inversion centers, and the latter form chains in the [001] direction. The overall hydrogen-bonded network is two-dimensional, with no propagation in the [100] direction. The packing in the is shown in Fig. 3 and includes also C—H⋯O interactions (Table 1).
Given the current understanding that de-acylation constitutes an important step in the expression of renal toxicity (Kankuri et al., 2003; Nohmi et al., 1984; Taxak et al., 2013), and the fact that the acyl group in bucetin (3-hydroxybutyryl) is much larger in size compared to the acetyl group in phenacetin and its congeners and has a chiral center, the information on the of bucetin presented here may help in the development of analgesics with little or no renal toxicity.
Synthesis and crystallization
The title compound, C12H17NO3 (bucetin; CAS No. 1083–57-4) was obtained from Sigma-Aldrich, St. Louis, MO and was used without further purification. Single crystals of racemic bucetin were prepared by slow cooling of a nearly of bucetin in boiling deionized water.
Refinement
Crystal data, data collection and structure .
details are summarized in Table 2
|
Structural data
CCDC reference: 2247342
https://doi.org/10.1107/S2414314623002316/vm4059sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314623002316/vm4059Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314623002316/vm4059Isup3.cml
Data collection: APEX2 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2017/1 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2020); software used to prepare material for publication: publCIF (Westrip, 2010).C12H17NO3 | F(000) = 480 |
Mr = 223.26 | Dx = 1.271 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54184 Å |
a = 12.2343 (4) Å | Cell parameters from 3666 reflections |
b = 9.6404 (3) Å | θ = 3.6–68.5° |
c = 9.9098 (3) Å | µ = 0.75 mm−1 |
β = 93.295 (2)° | T = 100 K |
V = 1166.86 (6) Å3 | Plate, colourless |
Z = 4 | 0.14 × 0.14 × 0.01 mm |
Bruker Kappa APEXII CCD DUO diffractometer | 2139 independent reflections |
Radiation source: IµS microfocus | 1739 reflections with I > 2σ(I) |
QUAZAR multilayer optics monochromator | Rint = 0.061 |
φ and ω scans | θmax = 68.5°, θmin = 3.6° |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | h = −14→14 |
Tmin = 0.832, Tmax = 0.993 | k = −11→11 |
14229 measured reflections | l = −11→11 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.116 | w = 1/[σ2(Fo2) + (0.0542P)2 + 0.4983P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
2139 reflections | Δρmax = 0.40 e Å−3 |
153 parameters | Δρmin = −0.23 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. All H atoms were located in difference maps and those on C were thereafter treated as riding in geometrically idealized positions with C—H distances 0.95 Å for phenyl, 0.98 Å for methyl, 0.99 Å for CH2, and 1.00 Å for methine. Coordinates of the N—H and O—H hydrogen atoms were refined. Uiso(H) values were assigned as 1.2Ueq for the attached atom (1.5 for methyl and OH). |
x | y | z | Uiso*/Ueq | ||
O1 | 0.93903 (10) | 0.38529 (13) | 0.33811 (12) | 0.0251 (3) | |
O2 | 0.56520 (10) | 0.51646 (12) | 0.76720 (12) | 0.0250 (3) | |
O3 | 0.43094 (10) | 0.37235 (13) | 0.97956 (12) | 0.0225 (3) | |
H3O | 0.4299 (17) | 0.421 (2) | 1.056 (2) | 0.034* | |
N1 | 0.54676 (12) | 0.35963 (15) | 0.59755 (15) | 0.0214 (3) | |
H1N | 0.5043 (17) | 0.295 (2) | 0.559 (2) | 0.026* | |
C1 | 0.64870 (14) | 0.36976 (17) | 0.53789 (17) | 0.0203 (4) | |
C2 | 0.73038 (14) | 0.46664 (17) | 0.57328 (17) | 0.0204 (4) | |
H2 | 0.720136 | 0.531692 | 0.643445 | 0.024* | |
C3 | 0.82674 (14) | 0.46737 (17) | 0.50532 (17) | 0.0214 (4) | |
H3A | 0.882226 | 0.533130 | 0.529774 | 0.026* | |
C4 | 0.84298 (14) | 0.37343 (18) | 0.40232 (17) | 0.0211 (4) | |
C5 | 0.76284 (15) | 0.27562 (18) | 0.36878 (18) | 0.0247 (4) | |
H5 | 0.773553 | 0.209619 | 0.299592 | 0.030* | |
C6 | 0.66716 (15) | 0.27482 (18) | 0.43681 (18) | 0.0236 (4) | |
H6 | 0.612697 | 0.207359 | 0.413541 | 0.028* | |
C7 | 0.51039 (14) | 0.42701 (17) | 0.70506 (17) | 0.0204 (4) | |
C8 | 0.39683 (15) | 0.38164 (18) | 0.74180 (18) | 0.0238 (4) | |
H8A | 0.342927 | 0.412240 | 0.669554 | 0.029* | |
H8B | 0.394699 | 0.279044 | 0.744956 | 0.029* | |
C9 | 0.36269 (15) | 0.43784 (18) | 0.87556 (18) | 0.0237 (4) | |
H9 | 0.375158 | 0.540341 | 0.878649 | 0.028* | |
C10 | 0.24341 (15) | 0.4077 (2) | 0.8973 (2) | 0.0291 (4) | |
H10A | 0.231907 | 0.307161 | 0.899454 | 0.044* | |
H10B | 0.197425 | 0.448185 | 0.823174 | 0.044* | |
H10C | 0.223748 | 0.448333 | 0.983239 | 0.044* | |
C11 | 0.95150 (15) | 0.29641 (19) | 0.22356 (19) | 0.0267 (4) | |
H11A | 0.886016 | 0.302629 | 0.160352 | 0.032* | |
H11B | 0.960301 | 0.198852 | 0.253434 | 0.032* | |
C12 | 1.05153 (16) | 0.3435 (2) | 0.1548 (2) | 0.0336 (5) | |
H12A | 1.042081 | 0.440295 | 0.126142 | 0.050* | |
H12B | 1.061736 | 0.285085 | 0.075633 | 0.050* | |
H12C | 1.115910 | 0.335942 | 0.217943 | 0.050* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0241 (7) | 0.0297 (7) | 0.0221 (7) | −0.0038 (5) | 0.0063 (5) | −0.0055 (5) |
O2 | 0.0345 (7) | 0.0209 (7) | 0.0204 (6) | −0.0026 (5) | 0.0082 (5) | −0.0018 (5) |
O3 | 0.0279 (7) | 0.0242 (7) | 0.0153 (6) | 0.0032 (5) | 0.0013 (5) | 0.0005 (5) |
N1 | 0.0241 (8) | 0.0217 (8) | 0.0186 (8) | −0.0041 (6) | 0.0036 (6) | −0.0017 (6) |
C1 | 0.0244 (9) | 0.0196 (9) | 0.0171 (9) | −0.0003 (6) | 0.0026 (7) | 0.0022 (6) |
C2 | 0.0266 (9) | 0.0177 (8) | 0.0168 (8) | −0.0010 (7) | 0.0020 (7) | −0.0006 (6) |
C3 | 0.0250 (9) | 0.0204 (9) | 0.0188 (9) | −0.0035 (7) | 0.0004 (7) | 0.0002 (6) |
C4 | 0.0217 (9) | 0.0241 (9) | 0.0177 (9) | 0.0000 (7) | 0.0029 (7) | 0.0025 (7) |
C5 | 0.0302 (10) | 0.0227 (9) | 0.0219 (9) | −0.0027 (7) | 0.0070 (7) | −0.0054 (7) |
C6 | 0.0282 (9) | 0.0209 (9) | 0.0222 (9) | −0.0070 (7) | 0.0050 (7) | −0.0032 (7) |
C7 | 0.0280 (9) | 0.0167 (8) | 0.0168 (8) | 0.0024 (7) | 0.0024 (7) | 0.0025 (7) |
C8 | 0.0261 (10) | 0.0247 (9) | 0.0208 (9) | −0.0002 (7) | 0.0016 (7) | 0.0012 (7) |
C9 | 0.0272 (10) | 0.0220 (9) | 0.0220 (9) | 0.0025 (7) | 0.0024 (7) | 0.0029 (7) |
C10 | 0.0267 (10) | 0.0327 (10) | 0.0283 (10) | 0.0003 (8) | 0.0053 (8) | 0.0033 (8) |
C11 | 0.0304 (10) | 0.0260 (10) | 0.0245 (10) | 0.0005 (7) | 0.0082 (8) | −0.0048 (7) |
C12 | 0.0330 (11) | 0.0381 (11) | 0.0312 (11) | −0.0024 (8) | 0.0135 (9) | −0.0070 (8) |
O1—C4 | 1.373 (2) | C6—H6 | 0.9500 |
O1—C11 | 1.437 (2) | C7—C8 | 1.521 (2) |
O2—C7 | 1.235 (2) | C8—C9 | 1.513 (2) |
O3—C9 | 1.435 (2) | C8—H8A | 0.9900 |
O3—H3O | 0.89 (2) | C8—H8B | 0.9900 |
N1—C7 | 1.345 (2) | C9—C10 | 1.515 (3) |
N1—C1 | 1.414 (2) | C9—H9 | 1.0000 |
N1—H1N | 0.88 (2) | C10—H10A | 0.9800 |
C1—C6 | 1.385 (2) | C10—H10B | 0.9800 |
C1—C2 | 1.398 (2) | C10—H10C | 0.9800 |
C2—C3 | 1.391 (2) | C11—C12 | 1.505 (3) |
C2—H2 | 0.9500 | C11—H11A | 0.9900 |
C3—C4 | 1.387 (2) | C11—H11B | 0.9900 |
C3—H3A | 0.9500 | C12—H12A | 0.9800 |
C4—C5 | 1.387 (3) | C12—H12B | 0.9800 |
C5—C6 | 1.384 (2) | C12—H12C | 0.9800 |
C5—H5 | 0.9500 | ||
C4—O1—C11 | 116.67 (13) | C7—C8—H8A | 108.7 |
C9—O3—H3O | 110.2 (14) | C9—C8—H8B | 108.7 |
C7—N1—C1 | 129.62 (15) | C7—C8—H8B | 108.7 |
C7—N1—H1N | 118.0 (14) | H8A—C8—H8B | 107.6 |
C1—N1—H1N | 112.2 (14) | O3—C9—C8 | 107.05 (14) |
C6—C1—C2 | 118.62 (16) | O3—C9—C10 | 109.82 (15) |
C6—C1—N1 | 116.18 (15) | C8—C9—C10 | 111.86 (15) |
C2—C1—N1 | 125.20 (16) | O3—C9—H9 | 109.4 |
C3—C2—C1 | 119.71 (16) | C8—C9—H9 | 109.4 |
C3—C2—H2 | 120.1 | C10—C9—H9 | 109.4 |
C1—C2—H2 | 120.1 | C9—C10—H10A | 109.5 |
C4—C3—C2 | 120.94 (16) | C9—C10—H10B | 109.5 |
C4—C3—H3A | 119.5 | H10A—C10—H10B | 109.5 |
C2—C3—H3A | 119.5 | C9—C10—H10C | 109.5 |
O1—C4—C5 | 123.90 (16) | H10A—C10—H10C | 109.5 |
O1—C4—C3 | 116.69 (15) | H10B—C10—H10C | 109.5 |
C5—C4—C3 | 119.40 (16) | O1—C11—C12 | 107.67 (15) |
C6—C5—C4 | 119.55 (16) | O1—C11—H11A | 110.2 |
C6—C5—H5 | 120.2 | C12—C11—H11A | 110.2 |
C4—C5—H5 | 120.2 | O1—C11—H11B | 110.2 |
C5—C6—C1 | 121.75 (16) | C12—C11—H11B | 110.2 |
C5—C6—H6 | 119.1 | H11A—C11—H11B | 108.5 |
C1—C6—H6 | 119.1 | C11—C12—H12A | 109.5 |
O2—C7—N1 | 122.49 (16) | C11—C12—H12B | 109.5 |
O2—C7—C8 | 123.98 (15) | H12A—C12—H12B | 109.5 |
N1—C7—C8 | 113.52 (15) | C11—C12—H12C | 109.5 |
C9—C8—C7 | 114.13 (15) | H12A—C12—H12C | 109.5 |
C9—C8—H8A | 108.7 | H12B—C12—H12C | 109.5 |
C7—N1—C1—C6 | 172.74 (17) | C4—C5—C6—C1 | 0.2 (3) |
C7—N1—C1—C2 | −7.1 (3) | C2—C1—C6—C5 | −1.4 (3) |
C6—C1—C2—C3 | 1.1 (2) | N1—C1—C6—C5 | 178.76 (16) |
N1—C1—C2—C3 | −178.98 (16) | C1—N1—C7—O2 | 2.5 (3) |
C1—C2—C3—C4 | 0.2 (3) | C1—N1—C7—C8 | −177.24 (16) |
C11—O1—C4—C5 | 4.6 (2) | O2—C7—C8—C9 | −9.6 (2) |
C11—O1—C4—C3 | −174.53 (15) | N1—C7—C8—C9 | 170.08 (15) |
C2—C3—C4—O1 | 177.82 (15) | C7—C8—C9—O3 | −68.25 (18) |
C2—C3—C4—C5 | −1.4 (3) | C7—C8—C9—C10 | 171.41 (15) |
O1—C4—C5—C6 | −177.96 (16) | C4—O1—C11—C12 | 170.14 (15) |
C3—C4—C5—C6 | 1.2 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3O···O2i | 0.89 (2) | 1.85 (2) | 2.7268 (17) | 167 (2) |
N1—H1N···O3ii | 0.88 (2) | 1.99 (2) | 2.8611 (19) | 169.7 (19) |
C2—H2···O2 | 0.95 | 2.32 | 2.908 (2) | 119 |
C3—H3A···O1iii | 0.95 | 2.60 | 3.482 (2) | 154 |
C6—H6···O2ii | 0.95 | 2.65 | 3.468 (2) | 145 |
C6—H6···O3ii | 0.95 | 2.48 | 3.269 (2) | 141 |
C8—H8B···O2iv | 0.99 | 2.58 | 3.553 (2) | 167 |
Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) x, −y+1/2, z−1/2; (iii) −x+2, −y+1, −z+1; (iv) −x+1, y−1/2, −z+3/2. |
Funding information
The authors acknowledge the support from the National Institutes of Health (NIH) through the National Institute of General Medical Science (NIGMS) grant No. 5 P2O GM103424–20 and the US Department of Education (US DoE; Title III, HBGI Part B grant No. P031B040030). Its contents are solely the responsibility of authors and do not represent the official views of NIH, NIGMS, or US DoE. The upgrade of the diffractometer was made possible by grant No. LEQSF(2011–12)-ENH-TR-01, administered by the Louisiana Board of Regents.
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