The structure and conformation of the tryptophanyl diketopiperazines cyclo(Trp–Trp)·C2H6SO and cyclo(Trp–Pro)

The structure and conformation of the cyclic dipeptides [cyclo(L-Trp–L-Trp)·C₂H₆SO] and cyclo(L-Trp–L-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Cyclo(L-tryptophanyl-L-tryptophanyl)·DMSO solvate crystallized in the space group P2 ₁2₁2₁ with cell dimensions a = 6.193(2), b = 11.545(3), c = 31.117(4) Å. The crystal structure is stabilized by four hydrogen bonds (three intermolecular hydrogen bonds and one intramolecular bond). The first intermolecular bond is between the oxygen of DMSO and the nitrogen of indole ring 2, in contrast to the second intramolecular hydrogen bond between the nitrogen of indole ring 1 and the oxygen of DMSO. The two remaining intermolecular hydrogen bonds are between the nitrogens of the DKP ring and the carbonyl oxygens of the DKP ring. The values of ^1A ₁ (–45.764) and ^1A ₂ (67.437) indicate an extended side chain conformation for Trp residue 1 (E_N) and a folded conformation for Trp residue 2. The DKP ring is more planar than in other cyclic dipeptide compounds (₁ = 11.414, ₁ = –7.516, ₂ = 12.471, and ₂ = –8.256). In cyclo(L-Trp–L-Trp) the C resonance of L-tryptophan (29.88 ppm) is shifted upfield 0.82 ppm when compared with the same resonance in cyclo(L-Trp–L-Gly) (30.7 ppm) and cyclo(L-Leu–L-Trp) (30.7 ppm). Two conformations of cyclo(Trp–Pro) crystallized in the space group P1 with cell dimensions a = 5.422(1), b = 9.902(1), c = 13.443(2) Å, = 80.42(1), = 78.61(1), and = 89.13(1)°. The conformation of the backbone and the orientation of the aromatic side chains for these conformers are very similar. The DKP rings for both conformers adopt a typical boat conformation in contrast to the flattened chair conformation observed for cyclo(Tyr–Pro) and cyclo(Phe–F-Pro). The tryptophan side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The pyrrolidine ring for conformer 1 can be described as an envelope (Cs–C-endo) conformation in contrast to the pyrrolidine ring symmetry for conformer 2 which is an intermediate between C_s and C₂ rather than pure C_s for the proline ring with C-endo and C-exo with respect to C. The two prolyl rings are puckered at the -carbon atoms which deviate from the best planes defined by the four remaining atoms. The crystal structures are stabilized by four intermolecular hydrogens bonds. An intermolecular bond between the nitrogen of the indole ring (conformer 1) and the carbonyl oxygen of the DKP ring (conformer 2) was observed. The second hydrogen bond is between the nitrogen of the indole ring (conformer 2) and the carbonyl oxygen of the DKP ring (conformer 1). The last two hydrogens involve the carbonyl oxygens of the DKP rings and the nitrogens of the DKP rings [carbonyl oxygen of DKP ring (conformer 1)––––nitrogen of DKP ring (conformer 2); nitrogen of DKP ring (conformer 1)––––––carbonyl oxygen of DKP ring (conformer 2)].     

Structure and conformation of the monohydrate of N-t-boctyrosyl-proline (Boc-Tyr-Pro·H2O)

The structure and conformation of the monohydrate of N-t-boc-tyrosyl-proline (Boc-Tyr-Pro·H₂O) (C₁₉H₂₆O₆N₂·H₂O) has been investigated with X-ray crystallographic and spectroscopic methods. Boc-Tyr-Pro crystallized in an extendedtrans conformation in the space group P2₁2₁2₁ with cell dimensionsa=8.566(1),b=9.996(1),c=24.734(1). The conformation of Boc-Tyr-Pro reflex -helix type prolines. Three intermolecular hydrogen bonds are observed. Crystal water is involved in two hydrogen bonds (to the hydroxyl group of the C-terminal of the proline residue; to the carbonyl group of the t-Boc functionality) while the hydroxyl group of the tyrosyl residue (to the carbonyl group of the amide bond) is involved in one hydrogen bond. The puckering mode of the pyrrolidine ring of the proline residue is similar to what has been previously observed for other proline-containing peptides.Cis-trans isomerism is observed in the NMR spectra of Boc-Tyr-Pro with a predominance for the extended side chain for the tyrosyl residue.     

Structure and conformation of the tripeptide: N-t-Boc-Prolyl-Phenylalanyl-Proline (Boc-Pro-Phe-Pro)

The structure and conformation of the tripeptide N-t-Boc-Prolyl-Phenylalanyl-Proline (Boc-Pro-Phe-Pro) (C₂₄H₃₃N₃O₆) have been investigated with X-ray crystallographic and spectroscopic methods. Two conformations of Boc-Pro-Phe-Pro crystallized in the space groupP2₁2₁2₁ with cell dimensionsa=11.912(1),b=14.256(1),c=30.402(3). The conformation of the backbone, the orientation of the aromatic side chain and the puckering modes for the pyrrolidine rings of these conformers differ significantly. The peptide bonds exist in the generally preferredtrans conformation being slightly non-planar. These two conformations reflect-helix- and collagen-type prolines. The crystal structures of both the conformers are stabilized by two, although different intermolecular hydrogen bonds. An intermolecular bond between the carbonyl oxygen of the carboxy terminal (³Pro) and the amide proton (²Phe) is observed for both the conformers. The second intermolecular hydrogen bond for conformer 1 is between the hydrogen of the carboxy terminal (³Pro) and the carbonyl oxygen of the N-t-Boc protecting group in contrast to the second hydrogen bond between the carbonyl oxygen of the (²Phe) residue and the hydrogen of the carboxy terminal (³Pro) for conformer 2. NMR spectroscopic studies indicated the presence of stereo-conformations due to thecis andtrans amide bonds similar to other proline-containing peptides.     

Crystal structure of diheterolevulosan II: α-d-Fructofuranose-β-d-fructopyranose 1,2′:2,1′ dianhydride and molecular mechanics calculations on diheterolevulosan II and IV with chair and boat conformations of the central 1,4-dioxane ring

C₁₂H₂₀O₁₀,M _r=324.28, orthorhombic,P2₁2₁2₁,a=9.4476(8),b=10.2247(8),c=13.5827(11) Å,V=1312.07(18) ų,Z=4,D _x=1.642 g cm^?3, MoKα radiation (λ=0.71073 Å)μ=1.4 cm^?1,F(000)=688,T=295 K, finalR=0.041 for 1089 reflections withI≥2.5σa(I). The molecule consists of aβ-d-fructopyranose and a α-d-fructofuranose ring which are linked by a 1,4-dioxane ring. The pyranose ring and the dioxane ring both have a chair conformation, and the furanose ring has an envelope conformation. All six hydroxyl groups act as donors in intermolecular hydrogen bonding. Each molecule is hydrogen-bonded to eight neighbor molecules by fourteen hydrogen bonds, forming a three-dimensional framework. The hydrogen bonds of varying geometry give rise to five sharp hydroxyl stretch vibrations in the infrared spectrum. In diheterolevulosan IV the central dioxane ring is a boat. Molecular mechanics calculations on diheterolevulosan II and IV having different boat and chair conformations of the dioxane ring show that the lowest energy conformations correspond to the conformations observed in the crystal structure. For comparison the calculations also have been applied to 1,4-dioxane having boat and chair conformations.     

X-Ray Crystallographic Structure of the Cyclic Di-amino Acid Peptide: <Emphasis Type="Italic">N,N</Emphasis>′-Diacetyl-cyclo(Gly-Gly)

Abstract  

The cyclic di-amino acid peptide N,N′-diacetyl-cyclo(Gly-Gly), C₈H₁₀N₂O₄, crystallizes in the triclinic space group P[`1] P\bar{1} with unit cell parameters a = 9.4855(4) ?, b = 10.0250(3) ?, c = 10.0763(4) ?, α = 73.682(2)°, β = 82.816(2)°, γ = 81.733(2)°, V = 906.40(6) ?<sup>3</sup>, Z = 4 (2 molecules, A and B, per asymmetric unit), D<sub>c</sub> = 1.452 g cm<sup>−3</sup> and linear absorption coefficient 0.118 mm<sup>−1</sup>. The crystal structure determination was carried out with MoKα X-ray data measured at 120(2) K. In the final refinement cycle the data/restraints/parameter ratios were 4124/0/258 and goodness-of-fit on F<sup>2</sup> = 1.0008. Final R indices for [I > 2σ(I)] were R<sub>1</sub> = 0.0501, wR<sub>2</sub> = 0.1007 and R indices (all data) R<sub>1</sub> = 0.0864, wR<sub>2</sub> = 0.11180. The largest electron density difference peak and hole were 0.241 and −0.232 e ?<sup>−3</sup>, respectively. The DKP rings in both molecules A and B have boat conformations with pseudo mm2 (C<sub>2v</sub>) symmetry if the N atoms and CH<sub>2</sub> groups are considered identical. In each case, the prow and stern of the boat are the α-carbons C(3) and C(6). The overall molecular symmetry of molecules A and B is approximately C<sub>2</sub> with the twofold symmetry axis of the DKP boat being maintained through the centre of the DKP ring. Details of the molecular geometry are compared with that of the parent compound cyclo(Gly-Gly) in which the DKP ring is planar with exact symmetry [`1] \bar{1} (C_i).     

Structure and conformation of the sodium chloride salt of N-t-Boc-Phenylalanyl-Proline (Boc-Phe-Pro·NaCl) and the dihydrate of N-t-Boc-Tyrosyl-Proline (Boc-Tyr-Pro·2H2O)

The structure and conformation of the salt of N-t-Boc-Phenylalanyl-Proline (Boc-Phe-Pro·NaCl) (C₁₉H₂₆N₂O₅NaCl) (compound 2) and the dihydrate of N-t-Boc-Tyrosyl-Proline (Boc-Tyr-Pro·2H₂O) (C₁₉H₃₀O₈N₂) (compound 1) have been investigated with X-ray crystallographic and spectroscopic methods. Boc-Phe-Pro·NaCl crystallizeds in an extended trans conformation in the space groupP2₁ with cell dimensionsa=7.961 (3),b=10.045(2), andc=13.495(4). One intermolecular hydrogen bond and one intramolecular hydrogen bond was observed for the dipeptide salt. Boc-Tyr-Pro·2H₂O crystallized in an extended trans conformation in the space group P2₁ with cell dimensionsa=7.964(1),b=10.011(1), andc=13.853(2). Six intermolecular hydrogen bonds were observed for Boc-Tyr-Pro·2H₂O. The conformation of both dipeptides reflect collagen-type of proline-compounds. The puckering mode of the pyrrolidine ring of the proline residues can be described as an approximate C₂ half-chair symmetry having an A conformation with the Cγ atom located exo and Cβ atom located endo relative to the carboxamide group, i.e., γ/β T.Cis-trans isomerism was observed in the NMR spectra of both dipeptides with a predominance for the extended side chain for the phenylalanyl and tyrosyl residues, respectively.     

Synthesis,Characterization, Crystal and Molecular Structure Analysis of 2,6-Dimethyl-3-acetyl-5-carbomethoxy-4-(3-nitrophenyl)-1,4-dihydropyridine

Abstract  A novel unsymmetrical dihydropyridine, possessing carboxymethyl and carbomethoxy groups at C(3) and C(5), respectively, has been produced using a modified Hantzsch synthesis, under solvent free conditions, in a domestic microwave oven. The product obtained was characterized by spectroscopic techniques and finally confirmed by X-ray diffraction studies. The title compound C₁₇H₁₈N₂O₅ crystallizes in the monoclinic system in the space group P2₁/c with cell parameters a = 12.860(2) ?, b = 7.4950(6) ?, c = 16.734(3) ?, β = 94.436(3)°, Z = 4 and V = 1608.1(4) ?³. The 1,4-dihydropyridine ring in the structure is in a flattened boat conformation. The molecule possesses a chiral center at C4. The 3-nitrophenyl ring is nearly orthogonal to the 1,4-dihydropyridine ring. The carbonyl groups at C3 and C5 are oriented in −antiperiplanar and +synperiplanar conformations, respectively. The structure exhibits both inter and intramolecular hydrogen bonds of the type N–H···O and C–H···O. Index Abstract  A novel unsymmetrical dihydropyridine, possessing carboxymethyl and carbomethoxy groups at C(3) and C(5) respectively, has been produced using a modified Hantzsch synthesis, under solvent free conditions, in a domestic microwave oven. The product obtained was characterized by spectroscipic techniques and finally confirmed by X-ray diffraction studies. The title compound C₁₇H₁₈N₂O₅ crystallizes in the monoclinic system in the space group P2_1/c with cell parameters a  =  12.860(2) ?, b  =  7.4950(6) ?, c  =  16.734(3) ?, β = 94.436(3)°, Z = 4 and V = 1608.1(4) ?³. The 1,4-dihydropyridine ring in the structure is in a flattened boat conformation. The molecule possesses a chiral center at C(4). The 3-nitrophenyl ring is nearly orthogonal to the 1,4-dihydropyridine ring. The carbonyl groups at C(3) and C(5) are oriented in −antiperiplanar and +synperiplanar conformations respectively. The structure exhibits both inter and intramolecular hydrogen bonds of the type N–H···O and C–H···O.

Crystal and Molecular Structures of Modified Progestagens (IV). 17α-Azidomethyl-17β-hydroxy-estra-4,9-dien-3-one,C19H25N3O2

The crystal and molecular structure of 17α-azidomethyl-17β-hydroxy-estra-4,9-dien-3-one has been determined by X-ray structure analysis. It crystallizes in the orthorhombie space group P 2₁2₁2₁ with cell parameters a = 9.118(1), b = 9.252(1), and c = 20.444(2) Å. The structure was solved by MULTAN-82 and refined to R = 0.042 for 1408 observed reflections. Steroid ring and 17β-side chain conformations are discussed in the paper. Intermolecular hydrogen bridges between hydroxyl groups and carbonyl oxygen atoms link molecules forming chains in c-direction.     

X-Ray Crystallographic Structure and Absolute Configuration of the Cyclic Di-amino Acid Peptide: Cyclo(<Emphasis Type="SmallCaps">l</Emphasis>-HomoCySH-<Emphasis Type="SmallCaps">l</Emphasis>-HomoCySH)

Abstract  

The cyclic di-amino acid peptide cyclo(l-homoCySH-l-homoCySH) [(3S, 6S)-3, 6-bis(2-sulfanylethyl) piperazine-2,5-dione, C₈H₁₄N₂O₂S₂, crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 6.1509(2) ?, b = 18.0217(9) ?, c = 29.6166(14) ?, V = 3283.0(2) ?³, Z = 12 (3 molecules, A, B and C, per asymmetric unit), D _c = 1.422 g cm⁻³ and a linear absorption coefficient of 0.464 mm⁻¹. The crystal structure determination was carried out with MoKα X-ray data measured at 120(2) K. In the final refinement cycle the data/restraints/parameter ratios were 5595/0/385 and goodness-of-fit on F ² = 1.084. Final R indices for [I > 2sigma(I)] were R1 = 0.0746, wR2 = 0.1356 and R indices (all data) R1 = 0.1092, wR2 = 0.1529. The largest electron density difference peak and hole were 0.526 and −0.445e ?⁻³. The DKP rings in all three molecules are essentially, and unusually, planar and the C=O oxygen atoms are co-planar with the ring in each case. Ring atom rms deviations, including the =O groups, are 0.0668, 0.0658 and 0.0656 ? in molecules A, B and C, respectively. Details of the molecular geometry are compared with the compound cyclo(Gly-Gly) (Degeilh R, Marsh RE Acta Cryst 12:1007, 1959) and in addition some cyclic di-amino acid peptides in which the DKP rings have more puckered boat conformations.     

Structure, absolute configuration, and conformation of the antimalarial drug artesunate

The crystal and molecular structure of the antimalarial compound artesunate has been determined by direct methods. Crystals are orthorhombic, P2₁2₁2₁, a = 9.8371(12), b = 10.517(2), c = 18.7594(5) Å, Z = 4, D _c = 1.316 mg/mL. The molecule is comprised of a fused ring system containing a six-membered ring C which includes an oxygen bridge and a peroxy bridge. The 9-atom oxygen–carbon chain from O(5)—C(12)... to ... O(2)—C(6) displays a striking sequence of short, long, short, long ... bonds while these distances are all within the ranges of a normal single bond or partial double bond. It is proposed that this pattern is caused by the delocalization of the lone pair electrons on the oxygen atoms. The ring C has a distorted boat conformation and the C—O—O—C torsion angle is 46.3(2)°. Rings A and D have ideal chair conformations. Ring junctions A/B and A/D are cis junctions, B/D and C/D are trans. Packing of the molecules is stabilized by one strong hydrogen bond involving the hydroxyl group on the ester linkage and the oxygen atom of the lactone ring.     

Configuration,conformation and crystal structure of rabdosianin b

Rabdosianin B, 7,20‐epoxy‐7β‐hydroxy‐1α,6β,11α,15β‐tetraacetoxy‐ent‐kaur‐16‐ene, C₂₈H₃₈O₁₀, was the first isolated from Isodon henryi. It consists of three six‐membered rings A, B, C and one five‐membered ring D. The fused‐ring system A, B and C are in chair, boat and chair conformations, respectively, and ring D is in an envelope conformation, on the basis of NMR and X‐ray diffraction analysis. The crystal of rabdosianin B is in orthorhombic crystal system with space group P2₁2₁2₁, lattice constants: a = 9.969(1) Å, b = 15.400(3) Å, and c = 17.624(3) Å, Z = 4. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The structure of ethyl allyl 1,4-dihydro-2,6-dimethyl-4-[4-(4H-4-oxo-1-benzopyran-2-yl)phenyl]-3,5-pyridine dicarboxylate

The crystal and molecular structure of the title compound has been determined by direct methods, and refined to a finalR of 0.070 for 1466 observed reflections. The compound crystallizes in space group P2_l/n with cell dimensionsa=10.706(8),b=21.127(11),c=12.038(10) Å, Z=4.1,4-dihydropyridine ring adopts a boat shaped conformation. The flavon molecule is planar and it's phenyl ring is almost perpendicular to the 1,4-DHP. The C36 atom of the allyl group shows disorder.     

Synthesis and crystal structure of 7,9-dideacetyl-1-deoxybaccatinVI

7,9-dideacetyl-1-deoxybaccatinVI was synthesized from 1-deoxybaccatinVI and its crystal structure was determined by X-ray crystallographic techniques. The compound (C₃₃H₄₂O₁₁·2CH₄O) crystallizes into monoclinic space group P2₁ with unit cell parameters: a=8.654(17) ?, b=16.470(5) ?, c=12.671(3) ?, β=97.63(2)°, and Z=2. The X-ray results demonstrated that the reaction of 7,9,10-Trideacetyl-1-deoxy-baccatinVI with Ac₂O in tetrahydrofuran, using CeCl₃ as catalyst, yielded monoacetylated product 7,9-dideacetyl-1-deoxy baccatinVI. In the structure, the six-membered A ring exhibits boat conformation, the eight-membered B ring adopts boat-chair conformation, and the six-membered C ring exhibits sofa conformation.     

Three-Six-Membered Rings with Diverse Conformations in the Structure of 9-(4-Methoxyphenyl)-3,3-Dimethyl-10-(4-Methylphenyl)-1,2,3,4,5,6,7,8,9,10-Decahydroacridin-1,8-Dione

Abstract  

The crystal structure of 9-(4-methoxyphenyl)-3,3-dimethyl-10-(4-methylphenyl)-1,2,3,4,5,6,7,8,9,10- decahydroacridin-1,8-dione is determined by X-ray diffraction at 153(2) K. The title compound 1, C₂₂H₂₁N₅O₆, is triclinic, space group P-1, a = 9.6382(15) ?, b = 11.5847(15) ?, c = 12.4722(11) ?, α = 66.075(9)°, β = 70.176(9)°, γ = 85.800(13)°, Z = 2, V = 1194.1(3) ?³. It is interesting that the central pyridine ring of the acridine moiety is slightly distorted and adopts a boat conformation. The outer six-membered ring with two methyl groups adopts half-chair conformation, while another outer partially saturated six-membered ring adopts distorted boat form. In addition, the un-classical hydrogen bonds of C–H···O link the molecules forming polymers in the crystals.     

Structural Conformation of a Novel Piperidine-4-One Derivative: 1-Acryloyl-3-Methyl-2,6-Dip-Tolylpiperidine-4-One

Abstract  

The novel 3-methyl-2,6-dip-toylpiperidine-4-one was acylated by 3-chloropropanoychloride and subjected for dehydrohalogenation. The synthesized compound was characterized by spectroscopic techniques and finally confirmed by X-ray diffraction studies. The molecule crystallizes in the monoclinic crystal class in the space group C ₂/c with cell parameters a = 18.538(2) ?, b = 9.9050(1) ?, c = 22.954(2) ?, β = 94.486(8)° and Z = 8. The piperidine ring adopts a twist boat conformation.     

Synthesis and Structural Studies of Novel Taxoids Derived from 1-DeoxybaccatinVI

Abstract  

Three novel taxoids were synthesized from 1-deoxybaccatinVI and their crystal structures were determined by X-ray crystallographic techniques. The influence of C(7), C(10) and C(4) substituents of the tetracyclic moiety on molecular conformations were investigated. The result shows that 4-acetyl moiety plays an important role in the conformation of the diterpenoid core. All of these 1-deoxybaccatinVI derivatives crystallize in orthorhombic system, space group P2₁2₁2₁. In the structures, the six-membered A ring exhibits the 1,4-di-planar conformation, the eight-membered B ring adopts boat–chair conformation and the six-membered C ring exhibits slightly distorted half-chair conformation.     

Crystal and molecular structure of trans‐(±)‐3‐acetoxy‐2‐(4‐methoxyphenyl)‐4‐oxo‐2,3,4,5‐tetrahydro‐1,5‐benzothiazepine‐1‐oxide

The title compound is a structurally related isomer of diltiazem, a well known drug. This compound (C₁₈H₁₇NO₅S) crystallizes in the space group P2₁/n with a = 13.803(4), b = 7.704(3), c = 16.093(3) Å, β = 105.37(2)º, Z = 4, V = 1650.1(9) ų. The least‐squares refinement gave residual index R = 0.067 for 2831 observed reflections. The distorted seven‐membered ring in the molecule shows twist‐boat conformation. Hydrogen bonds in which the amide group at one molecule and a carbonyl group in the adjacent molecule are involved to form centrosymmetric dimers in the crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations of dehydroepiandrosterone. Part I: crystal structure of sublimed DHEA

The crystal structure of an orthorhombic polymorph of the title compound, crystallized by sublimation, has been determined. Dehydroepiandrosterone, C₁₉H₂₈O₂, space groupP2₁2₁2₁ witha=6.6408(4)b=11.4423(11)c=22.085(2)Å,V=1678.2(4)ų,Z=4. The structure was refined toR=0.051 for 2645 observed reflections. The conformation of the molecule is similar to that found in other polymorphs and solvates, with a chair A ring, an 8, 9 half-chair B ring, a chair C ring, and a 14 envelope D ring. Molecules are linked in chains by OH...O hydrogen bonds involving the carbonyl oxygen atom. The O...O distance is 2.855(3) Å, and the angle about H is 171(2)^o.     

The molecular and crystal structure of endo-2-methyl-7-hydroxy-7-oxo-N-phenyl-7-phosphabicyclo-[2.2.1] hept-2-ene-5,6-dicarboximide

The structure of the title compound1 has been determined by X-ray crystallography analysis. The following crystal data were found: orthorhombic,Pca2_l,a=9.60691),b=16.356(1),c=8.686(1) . Both the phospholane and phospholene rings involved in the 7-phosphabicyclo-[2.2.1] hept-2-ene system have almost regular envelope conformations, and the cyclohexene ring has a significantly deformed boat conformation. The low value of the C–P–C angle, 84.2(2)°, reflects the steric strain around the phosphorus bridge and may be responsible for the reactivity of esters and amides derived from1 in the O-insertion reaction with m-chloro-perbenzoic acid. The dihedral angle between the plane of the benzene and succinimide rings is 82.4(2)°.     

X-ray structural and spectroscopic investigation of 1-piperidine-2,4-dinitrobenzene

The crystal structure of the title compound (C₁₁H₁₃N₃O₄) has been determined by single-crystal X-ray diffraction. The compound is monoclinic, space group P2₁/n, witha=9.968(2),b=9.156(2),c=13.249(2)Å, =102.05(2)°, andD _x=1.563 gcm^–3 forZ=4. The aromatic ring shows a slight boat deformation. Theo- andp-NO₂ groups are twisted out of the plane of the phenyl ring by 39.0(2)° and 4.4(1)°, respectively. The piperidine ring exhibits a slightly deformed chair conformation. Short C–H...O intermolecular contacts stabilize the three dimensional structure. UV and NMR data indicate that the molecule in solution presents a conformation similar to that of the the solid state.