In the crystal structure of the racemic title isoxazolidine, C19H27NO, the relative stereochemistry between the phenyl group and the bridgehead H atom is shown to be syn. There are two molecules in the asymmetric unit, one of which is the 7R*,13R* enantiomer, and one of which is the 7S*,13S* enantiomer. These enantiomers adopt different orientations of the phenyl ring with respect to the isoxazolidine ring, with C—C—C—C torsion angles of 63.6 (4) and 86.8 (4)°, respectively. In both enantiomers, the six-membered ring adopts a chair conformation, while the seven-membered ring adopts a twist-chair conformation.
In the title compound, C19H18Cl2O4, the two non-planar six-membered heterocycles passing through the spiro-C atom both adopt chair conformations, and the dihedral angle between the two benzene rings is 7.2 (1)°. In the crystal, the enantiomers with R and S configurations are generated by the symmetry elements of the centrosymmetric space group, forming a racemic crystal. Intermolecular C—H⋯π and weak C—H⋯O interactions link the molecules in the crystal structure.
The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring enantiopure lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid). The molecule contains four fused rings: three six-membered rings in chair conformations and one five-membered ring in a half-chair form. The two terminal six-membered rings are cis-fused, while other rings are trans-fused. The structure contains an intramolecular O—H⋯O hydrogen bond and a similar hydrogen-bond framework to the corresponding deoxycholic and chenodeoxycholic acid derivatives. Intermolecular O—H⋯O and N—H⋯O interactions are also present in the crystal. This compound seems to have at least two polymorphic forms from a comparison of the X-ray powder pattern simulated from the present structure of the title compound and that previously obtained for the powder sample.
The title compound, C33H49NO3, is the propargylamide of 18β-glycyrrhetinic acid, a pentacyclic triterpenoid of interest as a therapeutic agent. The five six-membered rings of the glycyrrhetinic acid moiety show normal geometries, with four rings in chair conformations and the unsaturated ring C in a half-chair conformation. In the crystal, the terminal N-propargylcarboxamide group has remarkable structural effects on weak hydrogen-bond-like interactions. Particularly noteworthy are an intermolecular O—H⋯π interaction accepted side-on by the terminal alkyne group [O⋯C = 3.097 (2) and 3.356 (2) Å] and a short intermolecular C—H⋯O interaction [C⋯O = 3.115 (2) Å] donated by the alkyne C—H group. An N—H⋯O [N⋯O = 3.251 (2) Å] and a Calkyl—H⋯O [C⋯O = 3.254 (2) Å] interaction complement the crystal structure.
The title compound, C34H52N2O7·CH4O, is the methanol solvate of a difunctionalized derivative of the therapeutic agent 18β-glycyrrhetinic acid, a pentacyclic triterpene. The five six-membered rings of the glycyrrhetinic acid moiety show normal geometries, with four rings in chair conformations and the unsaturated ring in a half-chair conformation. This moiety is substituted by a nitrate ester group and an O-ethylglycine group. In the crystal, the nonsolvent molecules are packed parallel to (010) in a herringbone fashion with the nitrato, ethylglycine and methanol-O atom being proximate. The methanol solvent molecule is anchored via a donated O—H⋯Oacyl and an accepted N—H⋯O hydrogen bond, giving rise to infinite zigzag chains of hydrogen bonds parallel to . Two weak intermolecular C—H⋯O interactions to the methanol and to an acyl oxygen establish links along  and , respectively.
The asymmetric unit of the title compound, C14H17NO4·1.25H2O, consists of four substituted pyrrolidone molecules (two pairs of enantiomers) and five water molecules. The five-membered rings each have an envelope conformation, with the C atom bonded to the ester group as the flap. The mean planes of the five-membered rings of the four pyrrolidone molecules make dihedral angles of 60.87 (5), 64.45 (5), 62.03 (5) and 65.79 (5)° with respect to the phenyl rings. In the crystal, the pyrrolidone and water molecules are connected through O—H⋯O hydrogen bonds, forming a layer parallel to the ab plane. The two-dimensional network is further stabilized by intermolecular C—H⋯O hydrogen bonds.
The bicyclic molecule of the title compound, C9H12O3, contains two five-membered rings with different functional groups, viz. a ketone and an ester. Both rings assume an envelope conformation. The mean planes of these functional groups form a dihedral angle of 60.7 (1)°. The crystal structure exhibits weak intermolecular C—H⋯O interactions, which link the molecules into zigzag chains extended in the  direction. The unit cell contains a racemic mixture of enantiomers.
The structure of the title compound, C26H28N2O2, contains essentially planar quinoline and benzene rings, the maximum deviations from the best plane being 0.086 (2) and 0.0056 (19) Å, respectively; the dihedral angle between the rings is 82.87 (4)°. The adamantane cage consists of three fused cyclohexane rings in classical chair conformations, with C—C—C angles in the range 107.85 (15)–111.35 (15)°. Enantiomers are linked alternately into chains along the c axis via short N—H⋯O interactions and further C–H⋯π interactions stabilize pairs of enantiomers, forming a two-dimensional network.
The crystal structure of the title compound, C26H21NO3·0.25H2O, reveals one stereogenic centre in the molecule. Nevertheless, due to the observed centrosymmetric space group, both enantiomers are present in the crystal packing. The water molecule of crystallisation is located on a crystallographic inversion center. The molecule contains one five-membered ring (A) and three six-membered rings (benzyl ring B, benzylidene ring C and formylbenzyl ring D). All four rings are not coplanar: the dihedral angles between rings A and B, A and C, and A and D are 70.35 (9), 33.8 (1) and 60.30 (9)°, respectively. In the crystal, pairs of weak C—H⋯O interactions lead to the formation of centrosymmetric dimers. Additional C—H⋯O interactions link the dimers into chains along .
In the cation of the title compound [systematic name: 1-(3-cyclohexyl-3-hydroxy-3-phenylpropyl)piperidinium chloride], C20H32NO+·Cl−, the cyclohexyl and piperidine rings are in chair conformations. In the crystal structure, cations and anions are linked into chains along the c-axis direction via O—H⋯Cl and N—H⋯Cl hydrogen bonds. Weak intermolecular C—H⋯Cl interactions link further these chains into layers parallel to the bc plane. The salt, obtained from a racemic solution, was found to crystallize in the chiral P21212 space group, indicating that, in the absence of any evident chirality-inducing process, the polycrystalline powders consist of an equivalent mixture of R and S enantiomers, forming a racemic conglomerate.
In the crystal structure of the title compound, C43H46NO13·0.5H2O, the molecule assumes a U-shaped conformation, the terminal benzene rings being approximately parallel and partially overlapped with each other. The molecule contains eight alicyclic and heterocyclic rings. The cyclohexane rings adopt chair conformations, the other three six-membered carbocyclic rings form a bicyclo[2.2.2]octane system with a boat conformation for each six-membered ring, the six-membered heterocyclic ring has a chair conformation and both of the five-membered rings have envelope conformations. The solvent water molecule links with the organic molecule via classic O—H⋯O and weak C—H⋯O hydrogen bonding in the crystal structure.
The title compound, C26H32O11, is composed of an α,β-unsaturated cyclohexanone ring (A), two cyclohexane rings (B and C), a six-membered lactone ring (D) and tetrahydrofuran ring (E). Ring A exists in a half-chair conformation with a C atom displaced by 0.679 (2) Å from the mean plane through the remaining five atoms. Ring B exists in a normal chair conformation. Both rings C and D exist in a twisted-chair conformation due to the O-atom bridge and the carbonyl group in rings C and D, respectively. Ring E shows an envelope conformation with a C atom displaced by 0.761 (1) Å from the mean plane through the remaining five atoms. The ring junctions are A/B trans, B/C trans, C/D cis and D/E cis. An intramolecular O—H⋯O hydrogen bond occurs. In the crystal, O—H⋯O hydrogen bonds involving the hydroxy, lactone and ester groups and C—H⋯O interactions are observed.
The title compound, C10H11Cl5O, is a chiral molecule with two stereogenic centres. However, it crystallizes as a racemate. One of enantiomers reveals the relative configuration (2S*,5R*). The cyclohexene ring adopts a half-chair conformation.
The title compound (delgradine), C41H43NO12, is a hetisine-type C20-diterpenoid alkaloid, isolated from the roots of Aconitum carmichaeli Debx. In the crystal structure, the molecule assumes an U-shaped conformation, the terminal benzene rings being approximately parallel and partially overlapped with each other. The molecule contains eight alicyclic and heterocyclic rings. Cyclohexane rings A and B adopt similar chair conformations; the six-membered rings C, D and E form a bicyclo[2.2.2]octane system with a boat conformation for each six-membered ring, the six-membered heterocyclic ring F has a screw-boat conformation and both of the five-membered rings G and H have envelope conformations. The crystal structure contains intermolecular O—H⋯O hydrogen bonding.
The title compound, C24H32N2O4, has a crystallographic inversion centre at the mid-point of the central C—C bond. At each end of the molecule, intramolecular O—H⋯N hydrogen bonds generate six-membered S(6) ring motifs. The crystal structure is stabilized by pairs of weak intermolecular C—H⋯O hydrogen bonds that link neighbouring molecules into R
2(40) ring motifs, which in turn form infinite one-dimensional supramolecular ribbon structures.
Eplerenone [systematic name: 7α-(methoxycarbonyl)-3-oxo-9α,11-epoxy-17α-pregn-4-ene-21,17-carbolactone], an aldosterone receptor antagonist, crystallizes from ethanol as a monosolvate, C24H30O6·C2H6O. The eplerenone molecule has two five-membered rings, three six-membered rings and one three-membered ring. Both five-membered rings display envelope conformations, while the three six-membered rings assume envelope (cyclohexene), half-chair (cyclohexane sharing one edge with epoxy) and chair (other cyclohexane) conformations. The solvent molecule is disordered equally over two sites. It is linked to the eplerenone molecule by hydrogen bonds.
The title compound, C24H30O5, is the didehydro product of the steroid hellebrigenin (systematic name: 3β,5,14-trihydroxy-19-oxo-5β-bufa-20,22-dienolide). It consists of three cyclohexane rings (A, B and C), a five-membered ring (D) and a six-membered lactone ring (E). The stereochemistry of the ring junctions are A/B cis, B/C trans and C/D cis. Cyclohexane rings A, B and C have normal chair conformations. The five-membered ring D with the C=C bond adopts an envelope conformation. Lactone ring E is essentially planar with a mean derivation of 0.006 (4) Å and is β-oriented at the C atom of ring D to which it is attached. There is an O—H⋯O hydrogen bond in the molecule involving the hydroxy groups. In the crystal, O—H⋯O hydrogen bonds link the molecules into chains propagating along . The chains are linked by C—H⋯O contacts into a three-dimensional network.
In the title compound, C28H32O2, the oxanone ring adopts distorted half-boat conformation with the following Cremer and Pople puckering parameters: Q = 0.619 (2) Å, θ = 0.75 (19) and ϕ = 172 (13)°. The dihedral angle betwen two benzene rings is 21.32 (7)°. The adamantane unit consists of three fused cyclohexane rings in classical chair conformations, with absolute values of C—C—C—C torsion angles in the range 57.5 (2)–60.9 (2)°. Weak interactions of the type C—H⋯O link molecules of each enantiomer into chains parallel to the b axis and lying about inversion centers. The crystal packing is also stabilized by intermolecular π-π stacking interactions [centroid–centroid distance of 3.8566 (11) Å].
The title compound [systematic name: 11β-hydroxy-24,25-epoxy-3,16-oxo-protost-13 (17)-en-23-yl acetate], C32H48O6, a protostane-type triterpenoid, was isolated from the Chinese herbal medicine alismatis rhizoma (the rhizome of Alisma orientalis Juzep). The molecule contains four trans-fused rings, viz. three six-membered and one five-membered ring. Two of the six-membered rings have slightly distorted half-chair conformations, while the third exhibits a chair conformation. The five-membered ring is almost planar. An intermolecular O—H⋯O hydrogen bond between the hydroxy and epoxy groups and intra- and intermolecular C—H⋯O hydrogen bonds are observed.
The title compound, C16H20O2, was synthesized to study the hydrogen-bonding interaction of the two enantiomers in the solid state. The racemate is made up of carboxylic acid RS dimers. Intermolecular O—H⋯O hydrogen bonds produce centrosymmetric R
2(8) rings which dimerize the two chiral enantiomers through their carboxyl groups. The chirality of this compound is generated by the presence of the double bond in the cyclohexene ring and a chiral axis due to the meta-methyl substituent on the aromatic ring.
In the racemic crystal of the title compound, C17H23NO, enantiomers of the two crystallographically independent molecules are linked into face-to-face RSdimers via intermolecular O—H⋯N hydrogen bonds and π–π interactions with centroid–centroid distances of 3.7610 (2) Å. The molecules adopt slightly different conformations and contain an adamantane cage consisting of three fused cyclohexane rings in almost ideal chair conformations, with C—C—C angles varying within the range 107.2 (4)–111.4 (4)°. In the hydrogen-bonded pair, the benzene rings are almost coplanar, the dihedral angle between them being 1.29 (13)°. The molecular packing in the crystal is stabilized by additional intermolecular N—H⋯O hydrogen bonds.
The title bis-piperidine, C26H28N2O3, was unexpectedly obtained via a dimerization mechanism promoted by acetic acid when performing the Dieckmann cyclization of a chiral amido ester. The S,S configuration was assigned by reference to the enantiomerically pure starting material. In the molecule, two core heterocycles are linked by a σ bond. One ring includes a keto–enol group, while the other presents an enone functionality. Both rings present a conformation intermediate between envelope and screw-boat, and the dihedral angle between the mean planes passing through the rings [48.9 (1)°] is large enough to avoid hindrance between ring substituents. The enol tautomeric form in one ring favors the formation of strong intermolecular O—H⋯O=C hydrogen bonds. The resulting one-dimensional supramolecular structure features single-stranded helices running along the 21 screw axis parallel to .
The title compound, C31H44O5, was synthesized from isosteviol (systematic name: ent-16-ketobeyeran-19-oic acid). In the molecule, the three six-membered rings adopt chair conformations and the stereochemistry of the A/B and B/C ring junctions are trans. The five-membered ring D adopts an envelope conformation with the methylene C atom as the flap.
In the title molecule, C28H44O, two six-membered rings have regular chair conformations, while the six-membered ring containing the C=C double bond exhibits a distorted chair conformation. The five-membered ring adopts an envelope conformation. In the crystal, weak intermolecular C—H⋯O interactions link molecules into chains along the b axis. The absolute configuration was assigned to correspond with that of the known chiral centres in a precursor molecule.
The title compound, C23H18N2O6, is the product of an intramolecular thermal cycloaddition within 1-malein-2-[(E)-2-(2-furyl)vinyl]-4-oxo-3,4-dihydroquinazoline. The molecule comprises a previously unknown fused pentacyclic system containing two five-membered rings (2-pyrrolidinone and furan) and three six-membered rings (benzene, 2,3-dihydro-4-pyrimidinone and dihydrocyclohexane). The central five-membered pyrrolidinone ring has the usual envelope conformation. The six-membered dihydropyrimidinone and dihydrocyclohexane rings adopt a half-boat and a half-chair conformation, respectively. The dihedral angle between the planes of the terminal benzene and furan rings is 45.99 (7)°. In the crystal, O—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. Weak C—H⋯O hydrogen bonds consolidate further the crystal packing, which exhibits π–π interactions, with a short distance of 3.556 (3) Å between the centroids of benzene rings of neighbouring molecules.