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1.  (±)-2′-Phenyl­cyclo­hexa­nespiro-4′-(aze­pano[1,2-b]isoxazolidine) 
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.
PMCID: PMC2962160  PMID: 21203240
2.  4,4′-Dimeth­oxy-2,2′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octa­hydro-1H-1,3-benzimidazole-1,3-diyl]bis(methyl­ene)}diphenol 
The title compound, C23H30N2O4, is a Mannich base useful for studying the effect of an electron-donating phenol substituent on intra­molecular hydrogen bonding. In the mol­ecular structure, the cyclo­hexane ring adopts a chair conformation and the five-membered ring has a twisted envelope conformation. Each meth­oxy group is oriented in the same plane of the respective aromatic ring, showing torsion angles below 11.8 (3)° and bond angles between the meth­oxy group and the aromatic ring of 116.6 (2) and 116.6 (1)°. The structure shows inter­actions between two the N atoms of the heterocyclic ring and the hy­droxy groups by intra­molecular O—H⋯N hydrogen-bonding inter­actions. In the crystal, C—H⋯O inter­actions are observed. The crystal studied was a racemic mixture of RR and SS enanti­omers.
PMCID: PMC3200725  PMID: 22065834
3.  (3aS,7aS)-5-[(S)-3,3,3-Trifluoro-2-meth­oxy-2-phenyl­propano­yl]-2,3,4,5,6,7-hexa­hydro-1H-pyrrolo[3,4-c]pyridin-3(2H)-one monohydrate 
rac-Benzyl 3-oxohexa­hydro-1H-pyrrolo[3,4-c]pyridine-5(6H)-carboxyl­ate was separated by chiral chromatography, and one of the enanti­omers ([α]22 D = +10°) was hydrogenated in the presence of Pd/C in methanol, producing octa­hydro-3H-pyrrolo[3,4-c]pyridin-3-one. The latter was reacted with (2R)-3,3,3-trifluoro-2-meth­oxy-2-phenyl­propanoyl chloride [(R)-(−)-Mosher acid chloride], giving rise to the title compound, C17H19F3N2O3·H2O. The present structure established the absolute configuration of the pyrrolopiperidine fragment based on the known configuration of the (R)-Mosher acid chloride. The piperidine ring has a somewhat distorted chair conformation and is cis-fused with the five-membered envelope-shaped ring; the plane of the exocyclic amide bond is approximately orthogonal to the plane of the phenyl ring, making a dihedral angle of 82.31 (3)°. The water mol­ecule acts as an acceptor to the proton of the amino group in an N—H⋯O inter­action, and as a double proton donor in O—H⋯O hydrogen bonds, generating infinite bands along the a axis.
PMCID: PMC2980001  PMID: 21580061
4.  rac-3,9-Bis(3-chloro­phen­yl)-2,4,8,10-tetra­oxaspiro­[5.5]undeca­ne 
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.
PMCID: PMC3201504  PMID: 22058783
5.  3α-Hydr­oxy-N-(3-hydroxy­prop­yl)-5β-cholan-24-amide 
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.
PMCID: PMC2968534  PMID: 21582298
6.  Propargylaminyl 3α-hy­droxy-11-oxo-18β-olean-12-en-29-oate 
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.
PMCID: PMC3247445  PMID: 22220063
7.  (3β,18β,20β)-N-Eth­oxy­carbonyl­methyl-3-nitrato-11-oxoolean-12-ene-29-carboxamide methanol monosolvate 
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 [100]. Two weak intermolecular C—H⋯O interactions to the methanol and to an acyl oxygen establish links along [100] and [010], respectively.
PMCID: PMC3344161  PMID: 22606164
8.  Ethyl 4-hy­droxy-1-methyl-5-oxo-2-phenyl­pyrrolidine-3-carboxyl­ate 1.25-hydrate 
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.
PMCID: PMC3569816  PMID: 23424562
9.  cis-3,3-Dimethyl-3,3a,4,5,6,6a-hexa­hydro-1H-cyclo­penta­[c]furan-1,6-dione 
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 [010] direction. The unit cell contains a racemic mixture of enanti­omers.
PMCID: PMC2961720  PMID: 21202900
10.  Triamcinolone acetonide acetate 
In the crystal structure of the title compound [systematic name: 2-(4b-fluoro-5-hy­droxy-4a,6a,8,8-tetra­methyl-2-oxo-2,4a,4b,5,6,6a,9a,10,10a,10b,11,12-dodeca­hydro-7,9-dioxa­penta­leno[2,1-a]phenanthren-6b-yl)-2-oxoethyl acetate], C26H33FO7, the mol­ecules are connected by inter­molecular O—H⋯O hydrogen bonds into an infinite supra­molecular chain along the b axis. The mol­ecular framework consists of five condensed rings, including three six-membered rings and two five-membered rings. The cyclo­hexa-2,5-dienone ring is nearly planar [maximum deviation = 0.013 (3) Å], while the cyclo­hexane rings adopt chair conformations. The two five-membered rings, viz. cyclo­pentane and 1,3-dioxolane, display envelope conformations.
PMCID: PMC3051574  PMID: 21523039
11.  3-(1-Adamantylamino)-3-methyl-1-phenyl­quinoline-2,4(1H,3H)-dione 
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.
PMCID: PMC2977340  PMID: 21583562
12.  (E)-4-[(1-Benzyl-4-benzyl­idene-2,5-di­oxopyrrolidin-3-yl)meth­yl]benzalde­hyde 0.25-hydrate 
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 [011].
PMCID: PMC3344122  PMID: 22606125
13.  Trihexyphenidyl hydro­chloride: a powder diffraction study 
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.
PMCID: PMC2983296  PMID: 21587506
14.  (1β,2α,3α,7α,11α,13β)-1,3,7,11-Tetra­acet­oxy-2,13-bis­(benz­yloxy)-21-methyl-19,21-secohetisan-19-al hemi­hydrate 
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.
PMCID: PMC2969740  PMID: 21583273
15.  Brusatol 
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.
PMCID: PMC3379203  PMID: 22719401
16.  rac-2-tert-Butyl-2,4,5,6,6-penta­chloro­cyclo­hex-3-en-1-one 
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.
PMCID: PMC3100040  PMID: 21754158
17.  2,2′-[1,1′-(Octane-1,8-diyldioxy­dinitrilo)diethyl­idyne]diphenol 
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 2(40) ring motifs, which in turn form infinite one-dimensional supra­molecular ribbon structures.
PMCID: PMC2970437  PMID: 21577782
18.  (1α,2β,3α,7α,11α,13β)-1,3,11-Triacet­oxy-2,13-bis­(benz­yloxy)-7-hydr­oxy-21-methyl-N,19-secohetisan-19-al 
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.
PMCID: PMC2962025  PMID: 21203114
19.  Eplerenone ethanol solvate 
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.
PMCID: PMC2961083  PMID: 21202318
20.  3-(1-Adamant­yl)-6-methyl-3-(3-methyl­benz­yl)isochroman-1-one 
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].
PMCID: PMC2969547  PMID: 21583062
21.  Tuberostemoamide hemihydrate 
In the crystal structure of the title compound {systematic name: (1′S,2R,2′R,3′S,6′R)-3′-ethyl-4-methyl-5H-5′-oxa-10′-aza­spiro­[furan-2,4′-tricyclo­[,6]trideca­ne]-5,11′-dione hemihydrate}, C17H23NO4·0.5H2O, the asymmetric unit contains two mol­ecules of tuberostemoamide with similar conformations and one water mol­ecule. The tuberostemoamide mol­ecule is composed of one seven-membered ring (A) and three five-membered rings (B, C and D). Ring A exists in a chair conformation, both rings B and C exist in envelope conformations, and ring D is almost planar with a mean deviation of 0.0143 (4) Å in one molecule and 0.0095 (3) Å in the other.. The dihedral angles between the planes of rings C and D are 75.1 (3)° in one mol­ecule and 74.5 (3)° for the other. The solvent water mol­ecule links the tuberostemoamide mol­ecules through O—H⋯O(ketone) hydrogen bonds. Weak C—H⋯O inter­actions are also present, involving both the water mol­ecule and a heterocyclic ether O-atom acceptor.
PMCID: PMC3247448  PMID: 22220066
22.  17-Deoxoestrone [estra-1,3,5(10)-trien-3-ol]–methanol (3/1) 
Three independent mol­ecules of the title estrone derivative and a mol­ecule of methanol comprise the asymmetric unit of the title compound [systematic name: 13-methyl-6,7,8,9,11,12,13,14,15,16-deca­hydro­cyclo­penta­[a]phenanthren-3-ol–meth­an­ol (3/1)], 3C18H24O·CH3OH. Two of the estrone mol­ecules exhibit 50:50 disorder (one displays whole-mol­ecule disorder and the other partial disorder in the fused five- and six-membered rings) so that five (partial) mol­ecular conformations are discernable. The conformation of the six-membered ring abutting the aromatic ring is close to a half-chair in all five components. The conformation of the six-membered ring fused to the five-membered ring is based on a chair with varying degrees of distortion ranging from minor to significant. Two distinct conformations are found for the five-membered ring: in four mol­ecules, the five-membered ring is twisted about the bond linking it to the six-membered ring, and in the other, the five-membered ring is an envelope with the quaternary C atom being the flap atom. The crystal packing features O—H⋯O hydrogen bonding whereby the four mol­ecules comprising the asymmetric unit are linked into a supra­molecular chain along the b axis.
PMCID: PMC3089339  PMID: 21754468
23.  14,15-Didehydro­hellebrigenin 
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 [010]. The chains are linked by C—H⋯O contacts into a three-dimensional network.
PMCID: PMC3379221  PMID: 22719419
24.  16-O-Methyl­cafestol 
The title compound [systematic name: (3bS,5aS,7R,8R,10aR,10bS)-7-meth­oxy-10b-methyl-3b,4,5,6,7,8,9,10,10a,10b,11,12-dodeca­hydro-5a,8-methano-5aH-cyclo­hepta­l[5,6]naph­tho[2,1-b]furan-7-methanol], C21H30O3, was isolated from the beans of Coffea robusta. The mol­ecule contains five fused rings including a furan ring. The two six-membered rings are in chair conformations, but the third six-membered ring and the five-membered aliphatic ring adopt envelope conformations. Inter­molecular O—H⋯O hydrogen bonding is present in the crystal structure.
PMCID: PMC2983991  PMID: 21580605
25.  2,6-Dimethyl-4-m-tolyl­cyclo­hex-3-enecarboxylic acid 
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 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.
PMCID: PMC2959375  PMID: 21201085

Results 1-25 (297758)