organic compounds
Low-temperature study of a new nevirapine pseudopolymorph
aInstituto de Física de São Carlos, Universidade de São Paulo, FFI/Grupo de Cristalografia, Avenida Trabalhador Saocarlense 400, Brazil, bAgencia Córdoba Ciencia, Córdoba, Argentina, and cDepartamento de Física, UFC, Fortaleza, CE, Brazil
*Correspondence e-mail: cecycarol@if.sc.usp.br
The title compound (systematic name: 11-cyclopropyl-4-methyl-5,11-dihydro-6H-dipyrido[3,2-b:2′,3′-e][1,4]diazepin-6-one butanol 0.3-solvate), C15H14N4O·0.3C4H9OH, was crystallized in a new triclinic pseudopolymorphic form, a butanol solvate, and the determined at 150 K. The molecular conformation of this new form differs from that reported previously, although the main intermolecular hydrogen-bond pattern remains the same. N—H⋯O hydrogen bonds [N⋯O = 2.957 (3) Å] form centrosymmetric dimers and the crystal packing of this new pseudopolymorph generates infinite channels along the b axis.
Related literature
For the et al. (1992). For spectroscopic studies of three further polymorphs, see: Reguri & Chakka (2005); World Health Organization (2005). For related literature, see: Ayala et al. (2007); Ren et al. (1995).
of an earlier polymorph, see: MuiExperimental
Crystal data
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Data collection: COLLECT (Nonius, 2000); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
https://doi.org/10.1107/S1600536807042262/bg2093sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536807042262/bg2093Isup2.hkl
NVP raw materials from different commercial sources were analyzed. USP standards of anhydrous and hemihydrate NEV were used as references.
All the hydrogen atoms were observed in the difference Fourier map, but positioned stereochemically (C—H: 0.95, C—H2: 0.97, C—H3:0.96, N—H: 0.88, O—H: 0.82 Å) and allowed to ride with isotropic displacement factors tied to those of their hosts by a factor of 1.2 (C—H, C—H2, N—H) and 1.5 (C—H3, O—H).
Nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2 - b:2',3'-e][1,4]diazepin-6-one) (NVP) is an antiretroviral drug that belongs to the non-nucleoside inhibitors class of the HIV-1 virus reverse transcriptase (NNRTI). Only one 1 (Figure 1), hereafter, Form V.
is known, reported by Mui et al., in the centrosymmetric P21/c (Form I) [Mui et al., 1992]. The literature also describes the existence of two polymorphs (Form II and III), useful as anti-psychotics, and one hemihydrate pseudopolymorph (Form IV). They were studied by X-ray powder diffraction, RAMAN and IR, but no studies are available yet [World Health Organization, 2005; Reguri & Chakka, 2005]. We report here, the of the pseudopolymorph butanol solvate of nervirapine, C15H14N4O*0.3(CH3OH), in the centrosymmetric PAs most of the NNRTIs, nevirapine displays a "butterfly like" conformation, which is also preserved in complexes with the HIV-1 reverse transcriptase [Ren et al., 1995]. Comparing the NVP conformations, it could be seen that the dihedral angle between the least square planes through the pyridine rings is 123.89 (9)°, somewhat larger than the one found by Mui et al., 121°, but still smaller than the one determined from the enzyme-inhibitor complex structure and ab initio calculations (129.22°) [Ayala et al., 2007].
An electron delocalization effect is presented by the amide moiety of the 7-membered ring, allowing this group to adopt a planar conformation with a C6—C5—N2—C4 torsion angle of -2.7 (4)° (slightly smaller than the one found for I, -4°) and to which the cyclopropyl substituent, evolving away from the molecular framework, subtends a dihedral angle of 68.5 (1)°.
The molecular superposition of I and V, calculated by minimizing the root square distance between the atoms of the 7-membered rings, shows that the main conformational differences are mainly concentrated in the cyclopropyl group, which presents C14—C13—N4—C10 and C15—C13—N4—C11 torsion angles of 81.9 (3)°, -69.9 (3)° in V, and 74.6°, -78.1° in I, respectively. In addiction, the superposition shows a small difference in conformation of the methyl substituted pyridine ring. The
in V is completed by the presence of a disordered butanol molecule with an occupation factor of 0.3.The analysis of the intermolecular interaction shows that, like in I, NEV molecules are linked essentially by two N—H···O hydrogen bonds, forming centrosymmetric dimers.
It is interesting to note that the main difference between both polymorphs is related to the crystal packing: while in I the intermolecular interaction generates a close packing with flat layers of nevirapine molecules separated by less than 4.4 Å, in V the three-dimensional arrangement generates infinite channels along de b axis with a diameter of more than 10.5 Å (Figure 2). These infinite channels are filled with highly disordered molecules of butanol, and this new Nevirapine form is stable even when a solvent occupation factor as low as 30%.
These findings indicate that a wide spectrum of new nevirapine pseudopolymorphs could be generated by just changing the solvent used in the crystallization process, as long as the volume of the solvent matches the available channel volume.
For the
of an earlier polymorph, see: Mui et al. (1992). For spectroscopic studies of three further polymorphs, see: Reguri & Chakka (2005); World Health Organization (2005). For related literature, see: Ayala et al. (2007); Ren et al. (1995).Data collection: COLLECT (Nonius, 2000); cell
SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK (Otwinowski & Minor, 1997) and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).C15H14N4O·0.3C4H10O | Z = 2 |
Mr = 288.54 | F(000) = 305.2 |
Triclinic, P1 | Dx = 1.254 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.8116 (6) Å | Cell parameters from 37940 reflections |
b = 8.4302 (7) Å | θ = 2.9–26.4° |
c = 12.5451 (11) Å | µ = 0.08 mm−1 |
α = 84.817 (5)° | T = 150 K |
β = 88.415 (5)° | Prism, colourless |
γ = 68.252 (4)° | 0.47 × 0.29 × 0.07 mm |
V = 764.18 (11) Å3 |
Nonius KappaCCD area-detector diffractometer | 2295 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.100 |
Horizonally mounted graphite crystal monochromator | θmax = 26.8°, θmin = 3.4° |
Detector resolution: 9 pixels mm-1 | h = −9→9 |
φ scans and ω scans winth κ offsets | k = −10→10 |
12941 measured reflections | l = −15→15 |
3141 independent reflections |
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)] = 0.075 | H-atom parameters constrained |
wR(F2) = 0.237 | w = 1/[σ2(Fo2) + (0.1266P)2 + 0.361P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max < 0.001 |
3141 reflections | Δρmax = 0.51 e Å−3 |
222 parameters | Δρmin = −0.24 e Å−3 |
28 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.37 (8) |
C15H14N4O·0.3C4H10O | γ = 68.252 (4)° |
Mr = 288.54 | V = 764.18 (11) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.8116 (6) Å | Mo Kα radiation |
b = 8.4302 (7) Å | µ = 0.08 mm−1 |
c = 12.5451 (11) Å | T = 150 K |
α = 84.817 (5)° | 0.47 × 0.29 × 0.07 mm |
β = 88.415 (5)° |
Nonius KappaCCD area-detector diffractometer | 2295 reflections with I > 2σ(I) |
12941 measured reflections | Rint = 0.100 |
3141 independent reflections |
R[F2 > 2σ(F2)] = 0.075 | 28 restraints |
wR(F2) = 0.237 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.51 e Å−3 |
3141 reflections | Δρmin = −0.24 e Å−3 |
222 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 | Occ. (<1) | |
C1 | 0.1486 (4) | 1.0251 (4) | 0.1362 (2) | 0.0486 (7) | |
H1 | 0.0843 | 1.1222 | 0.0887 | 0.058* | |
C2 | 0.2621 (4) | 1.0419 (4) | 0.2131 (2) | 0.0484 (7) | |
H2 | 0.2773 | 1.1481 | 0.2162 | 0.058* | |
C3 | 0.3543 (4) | 0.9043 (3) | 0.2859 (2) | 0.0446 (7) | |
C4 | 0.3290 (4) | 0.7507 (3) | 0.27637 (19) | 0.0413 (6) | |
C5 | 0.4871 (4) | 0.4427 (3) | 0.3419 (2) | 0.0429 (7) | |
C6 | 0.4937 (4) | 0.3825 (3) | 0.23304 (19) | 0.0412 (6) | |
C7 | 0.6468 (4) | 0.2423 (3) | 0.2073 (2) | 0.0445 (7) | |
H7 | 0.7470 | 0.1928 | 0.2563 | 0.053* | |
C8 | 0.6523 (4) | 0.1755 (4) | 0.1104 (2) | 0.0483 (7) | |
H8 | 0.7572 | 0.0819 | 0.0902 | 0.058* | |
C9 | 0.5019 (4) | 0.2482 (4) | 0.0438 (2) | 0.0473 (7) | |
H9 | 0.5058 | 0.2010 | −0.0226 | 0.057* | |
C10 | 0.3470 (4) | 0.4485 (3) | 0.15882 (19) | 0.0398 (6) | |
C11 | 0.2150 (4) | 0.7433 (3) | 0.19405 (19) | 0.0408 (6) | |
C12 | 0.4723 (5) | 0.9217 (4) | 0.3731 (2) | 0.0544 (8) | |
H12A | 0.4862 | 1.0328 | 0.3613 | 0.082* | |
H12B | 0.5939 | 0.8294 | 0.3725 | 0.082* | |
H12C | 0.4138 | 0.9142 | 0.4425 | 0.082* | |
C13 | 0.0187 (4) | 0.6077 (3) | 0.1266 (2) | 0.0427 (6) | |
H13 | 0.0156 | 0.6333 | 0.0471 | 0.051* | |
C14 | −0.0852 (4) | 0.4999 (4) | 0.1721 (2) | 0.0513 (7) | |
H14A | −0.0327 | 0.4195 | 0.2358 | 0.062* | |
H14B | −0.1522 | 0.4595 | 0.1216 | 0.062* | |
C15 | −0.1544 (4) | 0.6888 (4) | 0.1854 (2) | 0.0550 (8) | |
H15A | −0.2643 | 0.7643 | 0.1433 | 0.066* | |
H15B | −0.1448 | 0.7244 | 0.2573 | 0.066* | |
N1 | 0.1247 (3) | 0.8771 (3) | 0.12553 (17) | 0.0447 (6) | |
N2 | 0.4074 (3) | 0.6114 (3) | 0.35485 (16) | 0.0438 (6) | |
H2A | 0.4033 | 0.6390 | 0.4211 | 0.053* | |
N3 | 0.3494 (3) | 0.3815 (3) | 0.06598 (17) | 0.0438 (6) | |
N4 | 0.1863 (3) | 0.5888 (3) | 0.18231 (16) | 0.0406 (6) | |
O1 | 0.5584 (3) | 0.3371 (2) | 0.41782 (15) | 0.0558 (6) | |
O1S | −0.0302 (14) | 0.767 (2) | 0.4857 (14) | 0.151 (2) | 0.30 |
H1S | −0.1389 | 0.8162 | 0.5006 | 0.227* | 0.30 |
C1S | −0.0352 (18) | 0.1631 (17) | 0.4483 (10) | 0.080 (3) | 0.30 |
H11S | −0.1619 | 0.2166 | 0.4262 | 0.120* | 0.30 |
H12S | −0.0245 | 0.0799 | 0.5077 | 0.120* | 0.30 |
H13S | 0.0377 | 0.1074 | 0.3899 | 0.120* | 0.30 |
C2S | 0.036 (2) | 0.2730 (18) | 0.4746 (9) | 0.066 (3) | 0.30 |
H21S | 0.1625 | 0.1944 | 0.4872 | 0.079* | 0.30 |
H22S | −0.0175 | 0.2782 | 0.5454 | 0.079* | 0.30 |
C3S | 0.0709 (18) | 0.419 (2) | 0.4881 (14) | 0.109 (6) | 0.30 |
H31S | 0.1876 | 0.3703 | 0.5263 | 0.131* | 0.30 |
H32S | 0.1055 | 0.4342 | 0.4141 | 0.131* | 0.30 |
C4S | 0.019 (2) | 0.578 (2) | 0.5080 (18) | 0.151 (2) | 0.30 |
H41S | 0.1126 | 0.5594 | 0.5620 | 0.182* | 0.30 |
H42S | −0.0885 | 0.5808 | 0.5494 | 0.182* | 0.30 |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0560 (16) | 0.0426 (15) | 0.0444 (15) | −0.0156 (13) | 0.0005 (12) | −0.0005 (11) |
C2 | 0.0591 (17) | 0.0413 (14) | 0.0469 (15) | −0.0208 (13) | 0.0056 (13) | −0.0067 (11) |
C3 | 0.0519 (15) | 0.0423 (14) | 0.0412 (14) | −0.0189 (12) | 0.0041 (11) | −0.0067 (11) |
C4 | 0.0494 (15) | 0.0394 (14) | 0.0346 (12) | −0.0155 (11) | 0.0021 (11) | −0.0050 (10) |
C5 | 0.0534 (15) | 0.0420 (14) | 0.0343 (13) | −0.0187 (12) | −0.0031 (11) | −0.0031 (10) |
C6 | 0.0527 (15) | 0.0400 (14) | 0.0340 (13) | −0.0209 (12) | −0.0010 (11) | −0.0029 (10) |
C7 | 0.0497 (15) | 0.0437 (15) | 0.0412 (14) | −0.0182 (12) | −0.0021 (11) | −0.0033 (11) |
C8 | 0.0508 (16) | 0.0484 (16) | 0.0445 (15) | −0.0160 (13) | 0.0013 (12) | −0.0082 (12) |
C9 | 0.0535 (16) | 0.0506 (16) | 0.0380 (13) | −0.0184 (13) | 0.0008 (11) | −0.0095 (11) |
C10 | 0.0468 (14) | 0.0399 (13) | 0.0353 (12) | −0.0193 (11) | 0.0013 (10) | −0.0029 (10) |
C11 | 0.0493 (14) | 0.0393 (14) | 0.0338 (12) | −0.0163 (11) | 0.0015 (11) | −0.0034 (10) |
C12 | 0.0700 (19) | 0.0494 (17) | 0.0504 (16) | −0.0285 (15) | −0.0023 (14) | −0.0087 (13) |
C13 | 0.0461 (14) | 0.0468 (15) | 0.0364 (13) | −0.0177 (12) | −0.0007 (11) | −0.0069 (11) |
C14 | 0.0552 (17) | 0.0576 (18) | 0.0460 (15) | −0.0259 (14) | 0.0021 (12) | −0.0076 (13) |
C15 | 0.0492 (16) | 0.0623 (19) | 0.0524 (16) | −0.0167 (14) | 0.0000 (13) | −0.0163 (14) |
N1 | 0.0514 (13) | 0.0425 (12) | 0.0396 (12) | −0.0172 (10) | 0.0010 (10) | −0.0023 (9) |
N2 | 0.0568 (14) | 0.0426 (12) | 0.0313 (11) | −0.0172 (10) | −0.0010 (9) | −0.0048 (9) |
N3 | 0.0512 (13) | 0.0453 (13) | 0.0353 (11) | −0.0179 (10) | 0.0004 (9) | −0.0063 (9) |
N4 | 0.0489 (13) | 0.0398 (12) | 0.0340 (11) | −0.0168 (10) | −0.0026 (9) | −0.0049 (8) |
O1 | 0.0797 (15) | 0.0442 (11) | 0.0369 (10) | −0.0150 (10) | −0.0094 (9) | −0.0014 (8) |
O1S | 0.024 (3) | 0.217 (5) | 0.210 (5) | −0.017 (4) | 0.017 (4) | −0.131 (4) |
C1S | 0.067 (6) | 0.095 (7) | 0.060 (5) | −0.011 (5) | 0.008 (5) | −0.007 (5) |
C2S | 0.065 (6) | 0.080 (7) | 0.048 (5) | −0.026 (5) | 0.016 (4) | 0.009 (5) |
C3S | 0.022 (5) | 0.171 (15) | 0.100 (10) | 0.006 (8) | −0.011 (6) | −0.017 (10) |
C4S | 0.024 (3) | 0.217 (5) | 0.210 (5) | −0.017 (4) | 0.017 (4) | −0.131 (4) |
C1—N1 | 1.346 (3) | C12—H12C | 0.9800 |
C1—C2 | 1.379 (4) | C13—N4 | 1.450 (3) |
C1—H1 | 0.9500 | C13—C15 | 1.480 (4) |
C2—C3 | 1.387 (4) | C13—C14 | 1.496 (4) |
C2—H2 | 0.9500 | C13—H13 | 1.0000 |
C3—C4 | 1.396 (4) | C14—C15 | 1.504 (4) |
C3—C12 | 1.501 (4) | C14—H14A | 0.9900 |
C4—C11 | 1.403 (4) | C14—H14B | 0.9900 |
C4—N2 | 1.419 (3) | C15—H15A | 0.9900 |
C5—O1 | 1.232 (3) | C15—H15B | 0.9900 |
C5—N2 | 1.347 (3) | N2—H2A | 0.8800 |
C5—C6 | 1.493 (3) | O1S—C4S | 1.497 (17) |
C6—C7 | 1.390 (4) | O1S—H1S | 0.8200 |
C6—C10 | 1.408 (4) | C1S—C2S | 1.315 (15) |
C7—C8 | 1.379 (4) | C1S—H11S | 0.9600 |
C7—H7 | 0.9500 | C1S—H12S | 0.9600 |
C8—C9 | 1.372 (4) | C1S—H13S | 0.9600 |
C8—H8 | 0.9500 | C2S—C3S | 1.380 (16) |
C9—N3 | 1.343 (4) | C2S—H21S | 0.9700 |
C9—H9 | 0.9500 | C2S—H22S | 0.9700 |
C10—N3 | 1.336 (3) | C3S—C4S | 1.293 (15) |
C10—N4 | 1.416 (3) | C3S—H31S | 0.9700 |
C11—N1 | 1.333 (3) | C3S—H32S | 0.9700 |
C11—N4 | 1.422 (3) | C4S—H41S | 0.9700 |
C12—H12A | 0.9800 | C4S—H42S | 0.9700 |
C12—H12B | 0.9800 | ||
N1—C1—C2 | 122.9 (3) | C13—C14—C15 | 59.12 (19) |
N1—C1—H1 | 118.5 | C13—C14—H14A | 117.9 |
C2—C1—H1 | 118.5 | C15—C14—H14A | 117.9 |
C1—C2—C3 | 120.3 (3) | C13—C14—H14B | 117.9 |
C1—C2—H2 | 119.9 | C15—C14—H14B | 117.9 |
C3—C2—H2 | 119.9 | H14A—C14—H14B | 115.0 |
C2—C3—C4 | 117.3 (2) | C13—C15—C14 | 60.19 (19) |
C2—C3—C12 | 121.2 (2) | C13—C15—H15A | 117.8 |
C4—C3—C12 | 121.4 (2) | C14—C15—H15A | 117.8 |
C3—C4—C11 | 118.7 (2) | C13—C15—H15B | 117.8 |
C3—C4—N2 | 119.2 (2) | C14—C15—H15B | 117.8 |
C11—C4—N2 | 122.0 (2) | H15A—C15—H15B | 114.9 |
O1—C5—N2 | 121.4 (2) | C11—N1—C1 | 117.2 (2) |
O1—C5—C6 | 119.2 (2) | C5—N2—C4 | 129.0 (2) |
N2—C5—C6 | 119.5 (2) | C5—N2—H2A | 115.5 |
C7—C6—C10 | 117.9 (2) | C4—N2—H2A | 115.5 |
C7—C6—C5 | 117.8 (2) | C10—N3—C9 | 117.1 (2) |
C10—C6—C5 | 123.9 (2) | C10—N4—C11 | 114.7 (2) |
C8—C7—C6 | 119.6 (3) | C10—N4—C13 | 116.68 (19) |
C8—C7—H7 | 120.2 | C11—N4—C13 | 115.8 (2) |
C6—C7—H7 | 120.2 | C4S—O1S—H1S | 108.6 |
C9—C8—C7 | 118.0 (3) | C2S—C1S—H11S | 113.2 |
C9—C8—H8 | 121.0 | C2S—C1S—H12S | 109.4 |
C7—C8—H8 | 121.0 | H11S—C1S—H12S | 109.5 |
N3—C9—C8 | 124.6 (2) | C2S—C1S—H13S | 105.8 |
N3—C9—H9 | 117.7 | H11S—C1S—H13S | 109.5 |
C8—C9—H9 | 117.7 | H12S—C1S—H13S | 109.5 |
N3—C10—C6 | 122.8 (2) | C1S—C2S—C3S | 164.8 (16) |
N3—C10—N4 | 117.1 (2) | C1S—C2S—H21S | 98.8 |
C6—C10—N4 | 120.1 (2) | C3S—C2S—H21S | 95.5 |
N1—C11—C4 | 123.5 (2) | C1S—C2S—H22S | 92.2 |
N1—C11—N4 | 116.4 (2) | C3S—C2S—H22S | 89.7 |
C4—C11—N4 | 120.1 (2) | H21S—C2S—H22S | 103.2 |
C3—C12—H12A | 109.5 | C4S—C3S—C2S | 152.3 (18) |
C3—C12—H12B | 109.5 | C4S—C3S—H31S | 100.9 |
H12A—C12—H12B | 109.5 | C2S—C3S—H31S | 100.7 |
C3—C12—H12C | 109.5 | C4S—C3S—H32S | 97.0 |
H12A—C12—H12C | 109.5 | C2S—C3S—H32S | 94.3 |
H12B—C12—H12C | 109.5 | H31S—C3S—H32S | 104.1 |
N4—C13—C15 | 115.3 (2) | C3S—C4S—O1S | 158.0 (19) |
N4—C13—C14 | 116.6 (2) | C3S—C4S—H41S | 95.7 |
C15—C13—C14 | 60.7 (2) | O1S—C4S—H41S | 97.1 |
N4—C13—H13 | 117.3 | C3S—C4S—H42S | 96.0 |
C15—C13—H13 | 117.3 | O1S—C4S—H42S | 98.3 |
C14—C13—H13 | 117.3 | H41S—C4S—H42S | 103.6 |
N1—C1—C2—C3 | −1.8 (4) | C4—C11—N1—C1 | 1.1 (4) |
C1—C2—C3—C4 | 1.0 (4) | N4—C11—N1—C1 | 179.3 (2) |
C1—C2—C3—C12 | −177.4 (3) | C2—C1—N1—C11 | 0.7 (4) |
C2—C3—C4—C11 | 0.7 (4) | O1—C5—N2—C4 | 175.9 (3) |
C12—C3—C4—C11 | 179.1 (2) | C6—C5—N2—C4 | −2.5 (4) |
C2—C3—C4—N2 | −174.4 (2) | C3—C4—N2—C5 | −141.5 (3) |
C12—C3—C4—N2 | 4.0 (4) | C11—C4—N2—C5 | 43.5 (4) |
O1—C5—C6—C7 | −32.6 (4) | C6—C10—N3—C9 | −1.6 (4) |
N2—C5—C6—C7 | 145.8 (3) | N4—C10—N3—C9 | −179.9 (2) |
O1—C5—C6—C10 | 141.0 (3) | C8—C9—N3—C10 | 1.1 (4) |
N2—C5—C6—C10 | −40.5 (4) | N3—C10—N4—C11 | −118.4 (2) |
C10—C6—C7—C8 | 1.5 (4) | C6—C10—N4—C11 | 63.2 (3) |
C5—C6—C7—C8 | 175.6 (2) | N3—C10—N4—C13 | 21.7 (3) |
C6—C7—C8—C9 | −1.9 (4) | C6—C10—N4—C13 | −156.7 (2) |
C7—C8—C9—N3 | 0.6 (4) | N1—C11—N4—C10 | 119.0 (2) |
C7—C6—C10—N3 | 0.3 (4) | C4—C11—N4—C10 | −62.8 (3) |
C5—C6—C10—N3 | −173.4 (2) | N1—C11—N4—C13 | −21.5 (3) |
C7—C6—C10—N4 | 178.6 (2) | C4—C11—N4—C13 | 156.7 (2) |
C5—C6—C10—N4 | 4.9 (4) | C15—C13—N4—C10 | 150.4 (2) |
C3—C4—C11—N1 | −1.9 (4) | C14—C13—N4—C10 | 82.0 (3) |
N2—C4—C11—N1 | 173.1 (2) | C15—C13—N4—C11 | −70.0 (3) |
C3—C4—C11—N4 | −179.9 (2) | C14—C13—N4—C11 | −138.3 (2) |
N2—C4—C11—N4 | −4.9 (4) | C1S—C2S—C3S—C4S | 41 (7) |
N4—C13—C14—C15 | 105.5 (3) | C2S—C3S—C4S—O1S | −105 (6) |
N4—C13—C15—C14 | −107.6 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2A···O1i | 0.88 | Missing | 2.957 (3) | Missing |
Symmetry code: (i) −x, −y, −z. |
Experimental details
Crystal data | |
Chemical formula | C15H14N4O·0.3C4H10O |
Mr | 288.54 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 150 |
a, b, c (Å) | 7.8116 (6), 8.4302 (7), 12.5451 (11) |
α, β, γ (°) | 84.817 (5), 88.415 (5), 68.252 (4) |
V (Å3) | 764.18 (11) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.47 × 0.29 × 0.07 |
Data collection | |
Diffractometer | Nonius KappaCCD area-detector |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12941, 3141, 2295 |
Rint | 0.100 |
(sin θ/λ)max (Å−1) | 0.634 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.075, 0.237, 1.08 |
No. of reflections | 3141 |
No. of parameters | 222 |
No. of restraints | 28 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.51, −0.24 |
Computer programs: COLLECT (Nonius, 2000), SCALEPACK (Otwinowski & Minor, 1997) and DENZO (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2A···O1i | 0.88 | Missing | 2.957 (3) | Missing |
Symmetry code: (i) −x, −y, −z. |
Acknowledgements
This study was supported by CNPq, CAPES and UNESCO. The authors thanks Maribel Ferro for help in the crystallization process.
References
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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.
Nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2 - b:2',3'-e][1,4]diazepin-6-one) (NVP) is an antiretroviral drug that belongs to the non-nucleoside inhibitors class of the HIV-1 virus reverse transcriptase (NNRTI). Only one crystal structure is known, reported by Mui et al., in the centrosymmetric space group, P21/c (Form I) [Mui et al., 1992]. The literature also describes the existence of two polymorphs (Form II and III), useful as anti-psychotics, and one hemihydrate pseudopolymorph (Form IV). They were studied by X-ray powder diffraction, RAMAN and IR, but no crystal structure studies are available yet [World Health Organization, 2005; Reguri & Chakka, 2005]. We report here, the crystal structure of the pseudopolymorph butanol solvate of nervirapine, C15H14N4O*0.3(CH3OH), in the centrosymmetric space group P1 (Figure 1), hereafter, Form V.
As most of the NNRTIs, nevirapine displays a "butterfly like" conformation, which is also preserved in complexes with the HIV-1 reverse transcriptase [Ren et al., 1995]. Comparing the NVP conformations, it could be seen that the dihedral angle between the least square planes through the pyridine rings is 123.89 (9)°, somewhat larger than the one found by Mui et al., 121°, but still smaller than the one determined from the enzyme-inhibitor complex structure and ab initio calculations (129.22°) [Ayala et al., 2007].
An electron delocalization effect is presented by the amide moiety of the 7-membered ring, allowing this group to adopt a planar conformation with a C6—C5—N2—C4 torsion angle of -2.7 (4)° (slightly smaller than the one found for I, -4°) and to which the cyclopropyl substituent, evolving away from the molecular framework, subtends a dihedral angle of 68.5 (1)°.
The molecular superposition of I and V, calculated by minimizing the root square distance between the atoms of the 7-membered rings, shows that the main conformational differences are mainly concentrated in the cyclopropyl group, which presents C14—C13—N4—C10 and C15—C13—N4—C11 torsion angles of 81.9 (3)°, -69.9 (3)° in V, and 74.6°, -78.1° in I, respectively. In addiction, the superposition shows a small difference in conformation of the methyl substituted pyridine ring. The asymmetric unit in V is completed by the presence of a disordered butanol molecule with an occupation factor of 0.3.
The analysis of the intermolecular interaction shows that, like in I, NEV molecules are linked essentially by two N—H···O hydrogen bonds, forming centrosymmetric dimers.
It is interesting to note that the main difference between both polymorphs is related to the crystal packing: while in I the intermolecular interaction generates a close packing with flat layers of nevirapine molecules separated by less than 4.4 Å, in V the three-dimensional arrangement generates infinite channels along de b axis with a diameter of more than 10.5 Å (Figure 2). These infinite channels are filled with highly disordered molecules of butanol, and this new Nevirapine form is stable even when a solvent occupation factor as low as 30%.
These findings indicate that a wide spectrum of new nevirapine pseudopolymorphs could be generated by just changing the solvent used in the crystallization process, as long as the volume of the solvent matches the available channel volume.