Literature DB >> 26396756

Crystal structure of 1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-aminium 2-(4-iso-butyl-phen-yl)propano-ate: a simple organic salt of racemic ibuprofen.

Benyong Lou1.   

Abstract

In the title organic salt of ibuprofen with trometamol, C4H12NO3 (+)·C13H17O2 (-), the carb-oxy-lic acid group of ibuprofen has transferred its proton to the amino N atom of trometamol. In the crystal, the trometamol cations are linked via N-H⋯O hydrogen bonds, forming chains along [001]. To these chains are attached the ibuprofen anions via O-H⋯O and N-H⋯O hydrogen bonds. The chains are linked via further N-H⋯O and O-H⋯O hydrogen bonds, forming sheets parallel to (100). Two C atoms of the propano-ate substituent in the ibuprofen anion are disordered over two sets of sites and were refined with a fixed occupancy ratio of 0.7:0.3.

Entities:  

Keywords:  chains; crystal structure; hydrogen bonding; ibuprofen; mol­ecular salt; sheets; trometamol

Year:  2015        PMID: 26396756      PMCID: PMC4571357          DOI: 10.1107/S2056989015012979

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Salt formation is an effective approach for modifying the properties of active pharmaceutical ingredients (APIs) (Childs et al., 2007 ▸). Tris(hy­droxy­meth­yl)amino methane, commonly called trometamol, has been successfully exploited for improving the properties of APIs such as ketoprofen (Zippel & Wagenitz, 2006 ▸). In this study, trometamol was employed to crystallize with ibuprofen, giving rise to a new crystalline form, whose crystal structure is reported on herein.

Structural commentary

The mol­ecular structure of the title mol­ecular salt is shown in Fig. 1 ▸. From difference Fourier maps, it was shown that the carb­oxy­lic group of ibuprofen has transferred its proton to the amino N atom of trometamol. This is supported by the C—O bond distances of the carboxyl­ate group of the ibuprofen anion, which are 1.252 (2) and 1.251 (2) Å for C1—O1 and C1—O2, respectively. The carboxyl­ate anion inter­acts with one hydroxyl group of the trometamol cation through a strong hydrogen bond [O5O2 = 2.730 (2) Å; Table 1 ▸]. There also exist hydrogen-bonding inter­actions between the carboxyl­ate anion and aminium H atoms of the cation [N1⋯O1 = 2.763 (2) Å; Table 1 ▸].
Figure 1

The mol­ecular structure of the title mol­ecular salt, with atom labeling. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen bonds are shown as dashed lines (see Table 1 ▸ for details). The minor components of the disordered atoms (viz. C2 and C3) have been omitted for clarity in all three figures.

Table 1

Hydrogen-bond geometry (, )

DHA DHHA D A DHA
O3H3O2i 0.90(3)1.84(3)2.725(2)167(2)
O4H4O1ii 0.79(2)1.92(3)2.689(2)163.7(18)
O5H5AO10.86(2)2.57(2)3.0825(19)119.5(17)
O5H5AO20.86(2)1.88(2)2.730(2)168.1(18)
N1H1AO10.94(2)1.85(2)2.763(2)162.9(18)
N1H1BO4iii 0.94(2)2.09(2)2.9224(19)146.7(16)
N1H1CO5iv 0.91(2)1.97(2)2.806(2)152.1(18)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Supra­molecular features

In the crystal, the trometamol cations are linked via N—H⋯O hydrogen bonds, forming chains along [010]; Table 1 ▸ and Fig. 2 ▸. To these chains are attached the ibuprofen anions via N—H⋯O and O—H⋯O hydrogen bonds. The chains are linked via further O—H⋯O and N—H⋯O hydrogen bonds, forming sheets parallel to (100); Table 1 ▸ and Fig. 3 ▸.
Figure 2

Part of the crystal structure of the title salt, viewed along the c axis, showing the hydrogen bonds (dashed lines) forming chains along [001]; see Table 1 ▸ for details.

Figure 3

Part of the crystal structure of the title salt, viewed along the b axis, showing the sheets parallel to (100) formed by hydrogen bonding (dashed lines; see Table 1 ▸ for details).

Database survey

A search of the Cambridge Structural Database (Version 5.36, May 2015; Groom & Allen, 2014 ▸) revealed only one hit for organic salts of racemic ibuprofen, viz. benzyl­ammonium 2-(4-iso­butyl­phen­yl)propionate 2-(4-iso­butyl­phen­yl)propionic acid (refcode VUCHUX; Molnár et al., 2009 ▸). In fact, it is a salt co-crystal based on ibuprofen and the organic salt (Sun, 2013 ▸). The title compound is the first crystal structure of a simple organic salt of racemic ibuprofen.

Synthesis and crystallization

Ibuprofen (206 mg, 1 mmol) and trometamol (121 mg, 1 mmol) were dissolved in methanol (15 mL). The resulting solution was kept in air and after several days colorless plate-like crystals were obtained.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The hydroxyl and and aminium H atoms were located in difference Fourier maps and freely refined. Two C atoms, C3 and C2, of the propano­ate substit­uent in the ibuprofen anion are disordered over two sets of sites (C3/C3′and C2/C2′) and were refined with a fixed occupancy ratio of 0.7:0.3. H atoms H2 and H2′ were refined with distance restraints C—H = 0.98 (2) Å with U iso(H) = 1.2U eq(C). The remainder of the C-bound H atoms were positioned geometrically and refined as riding atoms: C—H = 0.95–1.00 Å with U iso(H) = 1.5U eq(C) for methyl H atoms and 1.2U eq(C) for other H atoms.
Table 2

Experimental details

Crystal data
Chemical formulaC4H12NO3 +C13H17O2
M r 327.41
Crystal system, space groupMonoclinic, P21/c
Temperature (K)173
a, b, c ()17.523(7), 10.400(4), 9.976(4)
()97.032(7)
V (3)1804.3(12)
Z 4
Radiation typeMo K
(mm1)0.09
Crystal size (mm)0.29 0.22 0.04
 
Data collection
DiffractometerRigaku Mercury CCD
Absorption correctionMulti-scan (CrystalClear; Rigaku, 2000)
T min, T max 0.914, 1.000
No. of measured, independent and observed [I > 2(I)] reflections13747, 4096, 3391
R int 0.028
(sin /)max (1)0.649
 
Refinement
R[F 2 > 2(F 2)], wR(F 2), S 0.058, 0.148, 1.11
No. of reflections4096
No. of parameters260
No. of restraints6
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
max, min (e 3)0.22, 0.23

Computer programs: CrystalClear (Rigaku, 2000 ▸), SHELXS97 and SHELXL97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and X-SEED (Barbour, 2001 ▸).

Crystal structure: contains datablock(s) I, Global. DOI: 10.1107/S2056989015012979/su5165sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015012979/su5165Isup2.hkl Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989015012979/su5165Isup3.cml CCDC reference: 1410786 Additional supporting information: crystallographic information; 3D view; checkCIF report
C4H12NO3+·C13H17O2F(000) = 712
Mr = 327.41Dx = 1.205 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 17.523 (7) ÅCell parameters from 4551 reflections
b = 10.400 (4) Åθ = 2.8–27.5°
c = 9.976 (4) ŵ = 0.09 mm1
β = 97.032 (7)°T = 173 K
V = 1804.3 (12) Å3Plate, colorless
Z = 40.29 × 0.22 × 0.04 mm
Rigaku Mercury CCD diffractometer4096 independent reflections
Radiation source: fine-focus sealed tube3391 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.028
Detector resolution: 28.5714 pixels mm-1θmax = 27.5°, θmin = 2.3°
CCD_Profile_fitting scansh = −22→22
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000)k = −13→13
Tmin = 0.914, Tmax = 1.000l = −12→12
13747 measured reflections
Refinement on F26 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.058H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.148w = 1/[σ2(Fo2) + (0.0646P)2 + 0.4122P] where P = (Fo2 + 2Fc2)/3
S = 1.11(Δ/σ)max = 0.001
4096 reflectionsΔρmax = 0.22 e Å3
260 parametersΔρmin = −0.23 e Å3
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.
xyzUiso*/UeqOcc. (<1)
O10.11773 (7)0.77640 (11)0.78429 (13)0.0439 (3)
O20.13430 (7)0.58002 (12)0.71039 (15)0.0544 (4)
C10.15768 (10)0.67741 (15)0.7767 (2)0.0422 (4)
C20.23375 (17)0.6782 (3)0.8754 (4)0.0408 (6)0.7
H20.2182 (17)0.670 (3)0.966 (2)0.049*0.7
C30.28440 (19)0.5630 (3)0.8537 (4)0.0610 (9)0.7
H3A0.29920.56600.76220.091*0.7
H3B0.25590.48350.86520.091*0.7
H3C0.33070.56540.91970.091*0.7
C2'0.2464 (4)0.6735 (7)0.8061 (9)0.0417 (16)0.3
H2'0.271 (3)0.616 (2)0.746 (6)0.050*0.3
C3'0.2585 (5)0.5894 (9)0.9312 (11)0.070 (2)0.3
H3'10.31150.59890.97440.105*0.3
H3'20.24900.49930.90550.105*0.3
H3'30.22280.61560.99450.105*0.3
C40.27435 (10)0.80792 (18)0.8575 (2)0.0542 (5)
C50.26039 (11)0.9010 (2)0.9485 (2)0.0540 (5)
H50.22810.88171.01570.065*
C60.29208 (11)1.0220 (2)0.9450 (2)0.0548 (5)
H60.28251.08301.01180.066*
C70.32041 (12)0.8410 (2)0.7599 (3)0.0667 (6)
H70.33150.77850.69550.080*
C80.35065 (13)0.9638 (2)0.7543 (3)0.0682 (6)
H80.38130.98430.68500.082*
C90.33732 (11)1.05711 (19)0.8470 (2)0.0549 (5)
C100.37079 (14)1.1906 (2)0.8433 (3)0.0768 (7)
H10A0.33441.25220.87680.092*
H10B0.37551.21310.74820.092*
C110.44861 (14)1.2067 (2)0.9256 (3)0.0768 (7)
H110.44381.17541.01900.092*
C120.4706 (2)1.3480 (3)0.9369 (4)0.1136 (12)
H12A0.47101.38420.84630.170*
H12B0.52191.35650.98780.170*
H12C0.43311.39450.98390.170*
C130.51137 (16)1.1303 (3)0.8743 (4)0.0991 (10)
H13A0.51861.16000.78340.149*
H13B0.49731.03910.87080.149*
H13C0.55931.14190.93480.149*
O3−0.15157 (8)0.82574 (12)0.84440 (14)0.0511 (4)
H3−0.1538 (14)0.910 (2)0.825 (2)0.081 (8)*
O4−0.08544 (7)0.44727 (12)0.91701 (13)0.0419 (3)
H4−0.0903 (12)0.387 (2)0.868 (2)0.066 (7)*
O5−0.00842 (7)0.64538 (11)0.58848 (12)0.0397 (3)
H5A0.0387 (12)0.6268 (18)0.616 (2)0.059 (6)*
N1−0.01557 (8)0.68283 (13)0.87045 (14)0.0313 (3)
H1A0.0234 (12)0.7199 (19)0.826 (2)0.049 (5)*
H1B0.0080 (11)0.6126 (19)0.9193 (19)0.044 (5)*
H1C−0.0290 (11)0.745 (2)0.927 (2)0.046 (5)*
C14−0.13080 (10)0.75903 (15)0.73082 (18)0.0411 (4)
H14A−0.09970.81570.67900.049*
H14B−0.17760.73350.67100.049*
C15−0.13077 (9)0.55121 (15)0.85901 (17)0.0367 (4)
H15A−0.15070.60120.93170.044*
H15B−0.17530.51680.79910.044*
C16−0.05760 (10)0.56874 (15)0.65824 (17)0.0370 (4)
H16A−0.03000.48950.69100.044*
H16B−0.10300.54300.59500.044*
C17−0.08440 (9)0.63973 (14)0.77797 (16)0.0310 (3)
U11U22U33U12U13U23
O10.0357 (6)0.0295 (6)0.0647 (8)−0.0003 (5)−0.0012 (6)0.0038 (6)
O20.0452 (7)0.0361 (7)0.0795 (10)0.0024 (5)−0.0018 (7)−0.0067 (6)
C10.0332 (8)0.0296 (8)0.0625 (12)−0.0022 (6)0.0010 (8)0.0099 (8)
C20.0370 (15)0.0368 (14)0.047 (2)0.0024 (11)0.0000 (14)0.0053 (15)
C30.0481 (18)0.0458 (16)0.084 (3)0.0132 (13)−0.0108 (17)0.0029 (18)
C2'0.038 (3)0.042 (3)0.046 (4)0.001 (2)0.007 (3)0.006 (3)
C3'0.054 (5)0.063 (5)0.087 (7)0.001 (4)−0.009 (4)0.022 (5)
C40.0293 (8)0.0450 (10)0.0838 (15)−0.0027 (7)−0.0115 (9)0.0023 (10)
C50.0395 (10)0.0578 (12)0.0636 (13)−0.0034 (8)0.0025 (9)0.0059 (10)
C60.0416 (10)0.0551 (11)0.0667 (14)−0.0019 (9)0.0028 (9)−0.0108 (10)
C70.0480 (12)0.0656 (13)0.0859 (17)−0.0039 (10)0.0058 (11)−0.0294 (12)
C80.0493 (12)0.0800 (16)0.0777 (16)−0.0129 (11)0.0180 (11)−0.0067 (13)
C90.0368 (9)0.0496 (11)0.0763 (15)−0.0067 (8)−0.0007 (9)−0.0016 (10)
C100.0570 (13)0.0523 (13)0.119 (2)−0.0110 (10)0.0007 (13)0.0100 (13)
C110.0639 (15)0.0552 (13)0.112 (2)−0.0196 (11)0.0132 (14)−0.0071 (13)
C120.097 (2)0.0659 (17)0.177 (4)−0.0342 (16)0.015 (2)−0.016 (2)
C130.0588 (16)0.094 (2)0.143 (3)−0.0092 (14)0.0058 (17)−0.006 (2)
O30.0624 (9)0.0323 (6)0.0598 (9)0.0120 (6)0.0124 (7)0.0012 (6)
O40.0542 (8)0.0286 (6)0.0411 (7)−0.0050 (5)−0.0013 (6)0.0064 (5)
O50.0401 (7)0.0417 (6)0.0372 (7)−0.0026 (5)0.0048 (5)0.0080 (5)
N10.0359 (7)0.0243 (6)0.0330 (8)−0.0003 (5)0.0014 (6)−0.0004 (6)
C140.0453 (10)0.0324 (8)0.0439 (10)0.0046 (7)−0.0021 (8)0.0023 (7)
C150.0387 (8)0.0306 (8)0.0406 (10)−0.0046 (6)0.0043 (7)0.0025 (7)
C160.0453 (9)0.0310 (8)0.0344 (9)−0.0065 (7)0.0041 (7)−0.0010 (7)
C170.0331 (8)0.0258 (7)0.0331 (8)−0.0017 (6)−0.0006 (6)0.0005 (6)
O1—C11.252 (2)C10—H10B0.9900
O2—C11.251 (2)C11—C131.497 (4)
C1—C2'1.547 (7)C11—C121.520 (3)
C1—C21.558 (4)C11—H111.0000
C2—C31.522 (4)C12—H12A0.9800
C2—C41.546 (4)C12—H12B0.9800
C2—H20.983 (17)C12—H12C0.9800
C3—H3A0.9800C13—H13A0.9800
C3—H3B0.9800C13—H13B0.9800
C3—H3C0.9800C13—H13C0.9800
C2'—C3'1.518 (11)O3—C141.414 (2)
C2'—C41.548 (8)O3—H30.90 (3)
C2'—H2'0.98 (2)O4—C151.422 (2)
C3'—H3'10.9800O4—H40.79 (2)
C3'—H3'20.9800O5—C161.4174 (19)
C3'—H3'30.9800O5—H5A0.86 (2)
C4—C51.369 (3)N1—C171.495 (2)
C4—C71.383 (3)N1—H1A0.94 (2)
C5—C61.377 (3)N1—H1B0.94 (2)
C5—H50.9500N1—H1C0.91 (2)
C6—C91.381 (3)C14—C171.526 (2)
C6—H60.9500C14—H14A0.9900
C7—C81.387 (3)C14—H14B0.9900
C7—H70.9500C15—C171.524 (2)
C8—C91.380 (3)C15—H15A0.9900
C8—H80.9500C15—H15B0.9900
C9—C101.509 (3)C16—C171.526 (2)
C10—C111.513 (4)C16—H16A0.9900
C10—H10A0.9900C16—H16B0.9900
O2—C1—O1123.26 (16)C11—C10—H10B108.6
O2—C1—C2'109.6 (3)H10A—C10—H10B107.6
O1—C1—C2'124.5 (3)C13—C11—C10114.0 (2)
O2—C1—C2122.54 (17)C13—C11—C12110.4 (2)
O1—C1—C2113.51 (18)C10—C11—C12110.5 (2)
C3—C2—C4112.7 (3)C13—C11—H11107.2
C3—C2—C1112.0 (3)C10—C11—H11107.2
C4—C2—C1107.6 (2)C12—C11—H11107.2
C3—C2—H2107.2 (18)C11—C12—H12A109.5
C4—C2—H2111.5 (17)C11—C12—H12B109.5
C1—C2—H2105.7 (18)H12A—C12—H12B109.5
C2—C3—H3A109.5C11—C12—H12C109.5
C2—C3—H3B109.5H12A—C12—H12C109.5
H3A—C3—H3B109.5H12B—C12—H12C109.5
C2—C3—H3C109.5C11—C13—H13A109.5
H3A—C3—H3C109.5C11—C13—H13B109.5
H3B—C3—H3C109.5H13A—C13—H13B109.5
C3'—C2'—C1101.9 (6)C11—C13—H13C109.5
C3'—C2'—C4103.9 (7)H13A—C13—H13C109.5
C1—C2'—C4108.0 (4)H13B—C13—H13C109.5
C3'—C2'—H2'97 (3)C14—O3—H3108.7 (12)
C1—C2'—H2'114 (4)C15—O4—H4109.7 (13)
C4—C2'—H2'127.3 (18)C16—O5—H5A109.7 (11)
C2'—C3'—H3'1109.5C17—N1—H1A114.1 (12)
C2'—C3'—H3'2109.5C17—N1—H1B110.8 (12)
H3'1—C3'—H3'2109.5H1A—N1—H1B105.3 (16)
C2'—C3'—H3'3109.5C17—N1—H1C110.3 (13)
H3'1—C3'—H3'3109.5H1A—N1—H1C104.9 (17)
H3'2—C3'—H3'3109.5H1B—N1—H1C111.3 (17)
C5—C4—C7117.28 (18)O3—C14—C17109.37 (14)
C5—C4—C2114.7 (2)O3—C14—H14A109.8
C7—C4—C2128.0 (2)C17—C14—H14A109.8
C5—C4—C2'141.6 (3)O3—C14—H14B109.8
C7—C4—C2'100.3 (3)C17—C14—H14B109.8
C4—C5—C6121.6 (2)H14A—C14—H14B108.2
C4—C5—H5119.2O4—C15—C17111.56 (13)
C6—C5—H5119.2O4—C15—H15A109.3
C5—C6—C9121.9 (2)C17—C15—H15A109.3
C5—C6—H6119.1O4—C15—H15B109.3
C9—C6—H6119.1C17—C15—H15B109.3
C4—C7—C8121.1 (2)H15A—C15—H15B108.0
C4—C7—H7119.5O5—C16—C17112.09 (12)
C8—C7—H7119.5O5—C16—H16A109.2
C9—C8—C7121.6 (2)C17—C16—H16A109.2
C9—C8—H8119.2O5—C16—H16B109.2
C7—C8—H8119.2C17—C16—H16B109.2
C8—C9—C6116.57 (19)H16A—C16—H16B107.9
C8—C9—C10122.1 (2)N1—C17—C15107.22 (13)
C6—C9—C10121.3 (2)N1—C17—C14107.80 (12)
C9—C10—C11114.6 (2)C15—C17—C14110.87 (13)
C9—C10—H10A108.6N1—C17—C16109.01 (13)
C11—C10—H10A108.6C15—C17—C16110.98 (12)
C9—C10—H10B108.6C14—C17—C16110.83 (14)
O2—C1—C2—C314.9 (4)C2—C4—C7—C8177.6 (2)
O1—C1—C2—C3−174.3 (3)C2'—C4—C7—C8171.4 (3)
O2—C1—C2—C4139.3 (2)C4—C7—C8—C91.2 (4)
O1—C1—C2—C4−50.0 (3)C7—C8—C9—C6−0.3 (3)
O2—C1—C2'—C3'−83.9 (6)C7—C8—C9—C10179.1 (2)
O1—C1—C2'—C3'114.1 (6)C5—C6—C9—C8−1.4 (3)
O2—C1—C2'—C4167.0 (4)C5—C6—C9—C10179.2 (2)
O1—C1—C2'—C45.0 (7)C8—C9—C10—C11−90.4 (3)
C3—C2—C4—C5−140.2 (3)C6—C9—C10—C1189.0 (3)
C1—C2—C4—C595.8 (3)C9—C10—C11—C1365.5 (3)
C3—C2—C4—C741.7 (4)C9—C10—C11—C12−169.5 (3)
C1—C2—C4—C7−82.2 (3)O4—C15—C17—N1−55.72 (17)
C3'—C2'—C4—C5−59.3 (7)O4—C15—C17—C14−173.15 (14)
C1—C2'—C4—C548.5 (8)O4—C15—C17—C1663.24 (18)
C3'—C2'—C4—C7132.5 (5)O3—C14—C17—N1−58.01 (17)
C1—C2'—C4—C7−119.7 (4)O3—C14—C17—C1559.06 (18)
C7—C4—C5—C6−1.3 (3)O3—C14—C17—C16−177.23 (13)
C2—C4—C5—C6−179.6 (2)O5—C16—C17—N1−56.68 (17)
C2'—C4—C5—C6−168.2 (5)O5—C16—C17—C15−174.56 (13)
C4—C5—C6—C92.3 (3)O5—C16—C17—C1461.80 (18)
C5—C4—C7—C8−0.4 (3)
D—H···AD—HH···AD···AD—H···A
O3—H3···O2i0.90 (3)1.84 (3)2.725 (2)167 (2)
O4—H4···O1ii0.79 (2)1.92 (3)2.689 (2)163.7 (18)
O5—H5A···O10.86 (2)2.57 (2)3.0825 (19)119.5 (17)
O5—H5A···O20.86 (2)1.88 (2)2.730 (2)168.1 (18)
N1—H1A···O10.94 (2)1.85 (2)2.763 (2)162.9 (18)
N1—H1B···O4iii0.94 (2)2.09 (2)2.9224 (19)146.7 (16)
N1—H1C···O5iv0.91 (2)1.97 (2)2.806 (2)152.1 (18)
  7 in total

1.  The salt-cocrystal continuum: the influence of crystal structure on ionization state.

Authors:  Scott L Childs; G Patrick Stahly; Aeri Park
Journal:  Mol Pharm       Date:  2007-04-27       Impact factor: 4.939

2.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

3.  The Cambridge Structural Database in retrospect and prospect.

Authors:  Colin R Groom; Frank H Allen
Journal:  Angew Chem Int Ed Engl       Date:  2014-01-02       Impact factor: 15.336

Review 4.  Cocrystallization for successful drug delivery.

Authors:  Changquan Calvin Sun
Journal:  Expert Opin Drug Deliv       Date:  2012-12-21       Impact factor: 6.648

5.  Comparison of the efficacy and safety of intravenously administered dexketoprofen trometamol and ketoprofen in the management of pain after orthopaedic surgery: A multicentre, double-blind, randomised, parallel-group clinical trial.

Authors:  H Zippel; A Wagenitz
Journal:  Clin Drug Investig       Date:  2006       Impact factor: 2.859

6.  Influence of benzylamine on the resolution of ibuprofen with (+)-(R)-phenylethylamine via supercritical fluid extraction.

Authors:  Péter Molnár; Petra Bombicz; Csaba Varga; Laura Bereczki; Edit Székely; György Pokol; Elemér Fogassy; Béla Simándi
Journal:  Chirality       Date:  2009-06       Impact factor: 2.437

7.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

  7 in total

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