4‐Ethoxycarbonyl‐3‐hydroxy‐3‐phenylcyclohexanone

The title compound, ethyl 2‐hydroxy‐4‐oxo‐2‐phenyl­cyclo­hexane­carboxyl­ate, C₁₅H₁₈O₄, was obtained by a Michael–Aldol condensation and has the cyclo­hexanone in a chair conformation. The attached hydroxy, ethoxy­carbonyl and phenyl groups are disposed in β‐axial, β‐equatorial and α‐­equatorial configurations, respectively. An intermolecular hydrogen bond, with an O?O distance of 2.874 (2) Å, links the OH group and the ring carbonyl. Weak intermolecular C—H?O=C (ester and ketone), O—H?O=C (ketone) and C—H?OH hydrogen bonds exist.     

24(R)‐Acetyl­oxy‐1α,2α‐epoxy­cholesta‐4,6‐dien‐3‐one hydrate

In the title compound, C₂₉H₄₂O₄·H₂O, cyclo­hexane rings A and B are in the sofa conformation, ring C is in a chair conformation and the five‐membered ring D is in an envelope conformation. The structure is stabilized by inter‐ and intramolecular C—H?O and O—H?O hydrogen bonds.     

Chiral and meso‐bis([2.2]­para­cyclo­phan‐4‐yl)­methane and meso‐bis­([2.2]­para­cyclo­phan‐4‐yl) sulfide

The [2.2]­para­cyclo­phane groups of the title compounds, chiral and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl)­methane (the former as a racemate), C₃₃H₃₂, and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl) sulfide, C₃₂H₃₀S, show the characteristic structural features of the parent compound [2.2]­para­cyclo­phane and the related compound di­methylbis([2.2]­para­cyclo­phan‐4‐yl)­silane, C₃₄­H₃₆­Si: the aromatic rings are puckered, resulting in a boat conformation. The planes of the four coplanar C atoms are slightly twisted with respect to each other. The Csp³—Csp³ bond lengths of the ethyl­ene bridges are elongated by the electronic and steric effects of the skeleton.     

3‐(p‐Chloro­phenyl)‐4‐phenyl‐4,5‐di­hydro­isoxazole‐5‐spiro‐2′‐1′,2′,3′,4′‐tetra­hydro­naphthalen‐1′‐one

In the title compound, C₂₄H₁₈ClNO₂, the phenyl ring and the tetralone moiety are approximately orthogonal to the isoxazoline ring. The isoxazoline ring adopts an envelope conformation, while the cyclo­hexenone ring of the tetralone moiety has an intermediate sofa/half‐chair conformation. In this structure, one C—H?N intermolecular and two C—H?O intramolecular hydrogen bonds occur; the H?A distances are 2.60, and 2.35 and 2.57 Å, respectively. The mol­ecules are held together by an intermolecular C—H?N hydrogen bond, forming a one‐dimensional chain along the [100] direction.     

Precursor of a β‐lactamase inhibitor: allyl (4S,8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.03,8]­undec‐2‐ene‐2‐carboxyl­ate

The molecular structure of the title tricyclic compound, C₁₇H₂₁NO₄, which is the immediate precursor of a potent synthetic inhibitor {Lek157: sodium (8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.0^3,8]­undec‐2‐ene‐2‐carboxyl­ate} with remarkable potency, provides experimental evidence for the previously modelled relative position of the fused cyclo­hexyl ring and the carbonyl group of the β‐lactam ring, which takes part in the formation of the initial tetrahedral acyl–enzyme complex. In this hydro­phobic mol­ecule, the overall geometry is influenced by C—H?O intramolecular hydrogen bonds [3.046 (4) and 3.538 (6) Å, with corresponding normalized H?O distances of 2.30 and 2.46 Å], whereas the mol­ecules are interconnected through intermolecular C—H?O hydrogen bonds [3.335 (4)–3.575 (5) Å].     

(1R,3S)‐Camphoramic acid

The title chiral compound, 3‐amino­carbonyl‐1,2,2‐tri­methyl­cyclo­pentane‐1‐carboxylic acid, C₁₀H₁₇NO₃, was prepared from (1R,3S)‐camphoric acid. The five‐membered ring adopts a conformation which is intermediate between a twist and an envelope. Elongations of the C—C bonds and contractions of the C—C—C bond angles are observed within the five‐membered ring. A ¹H NMR spectrum was recorded to assist in distinguishing the amide group from the carboxyl group.     

9,9‐Dimethoxy‐7,11‐diphenyl‐2,4‐diazaspiro[5.5]undecane‐1,3,5‐trione monohydrate

Due to steric repulsions, the cyclo­hexane ring in the title compound, C₂₃H₂₄N₂O₅·H₂O, shows some bond‐length abnormalities and adopts a chair conformation. The pyrimidine and cyclo­hexane rings are approximately perpendicular to each other, and the phenyl rings are equatorial. C—H?π and N—H?O intermolecular interactions, as well as C—H?O inter‐ and intramolecular interactions, occur between the mol­ecules. In addition to van der Waals interactions, the water mol­ecule interacts with the pyrimidine­trione ring to stabilize the structure.     

Secondary interactions in n‐(chloromethyl)pyridinium chlorides (n = 2, 3, 4)

In the isomeric title compounds, viz. 2‐, 3‐ and 4‐(chloro­methyl)pyridinium chloride, C₆H₇ClN⁺·Cl^?, the secondary interactions have been established as follows. Classical N—H?Cl^? hydrogen bonds are observed in the 2‐ and 3‐isomers, whereas the 4‐isomer forms inversion‐symmetric N—H(?Cl^??)₂H—N dimers involving three‐centre hydrogen bonds. Short Cl?Cl contacts are formed in both the 2‐isomer (C—Cl?Cl^?, approximately linear at the central Cl) and the 4‐isomer (C—Cl?Cl—C, angles at Cl of ca 75°). Additionally, each compound displays contacts of the form C—H?Cl, mainly to the Cl^? anion. The net effect is to create either a layer structure (3‐isomer) or a three‐dimensional packing with easily identifiable layer substructures (2‐ and 4‐isomers).     

Two polycyclic compounds derived from a Diels–Alder reaction

In both 9,10‐di­methoxy‐11‐oxatri­cyclo­[6.2.1.0^2,7]­undeca‐4,9‐diene‐3,6‐diol, C₁₂H₁₆O₅, (I), and 5,6‐di­methoxy‐3,7‐dioxa­tetra­cyclo­[6.4.0.0^2,6.0^4,12]­dodec‐9‐en‐11‐ol, C₁₂H₁₆O₅, (II), the hetero‐oxygen‐containing five‐membered rings have an envelope conformation. The six‐membered rings are in a boat conformation in compound (I), and in (II), one is in a half‐boat and the other is in a slightly distorted boat conformation. The mol­ecules in both compounds interact through classical hydrogen bonds and C—H?O contacts.     

2,2′‐Methyl­enebis(3‐hydroxy‐2‐cyclo­hexen‐1‐one)

In the title compound, C₁₃H₁₆O₄, the cyclo­hexene rings adopt a sofa conformation. Adjacent mol­ecules are connected by C—H?O intermolecular interactions. Each mol­ecule is characterized by O—H?O intramolecular hydrogen bonds. The anti arrangement of the enolic OH group and the carbonyl O atom in the solid state is similar to the anti arrangement of the NH and carbonyl groups in indigo.     

16‐(4‐Iso­propyl­benzyl­idene)­androst‐4‐ene‐3,17‐dione

In the title compound, C₂₉H₃₆O₂, the outer cyclohexene ring of the steroid nucleus has a conformation that lies about half‐way between a half‐chair and an envelope, while the central and outer cyclo­hexane rings of the steroid nucleus have slightly distorted chair conformations. The steroidal cyclo­pentane ring adopts a 13β,14α‐half‐chair conformation. The benzyl­idene moiety has an E configuration with respect to the carbonyl group on the cyclo­pentane ring. The dihedral angle between the mean planes of the steroid nucleus and the benzyl­idene moiety is 35.54 (9)°. The packing of the mol­ecules is assumed to be dictated mainly by weak intermolecular C—H⋯O interactions.     

Ferrocene compounds. XXXIX.

In the title compound, [Fe(C₅H₅)(C₁₄H₁₃O)], the plane of the heterocyclic ring is almost perpendicular to the plane of the substituted cyclo­penta­dienyl ring, and the heterocyclic ring adopts a half‐chair conformation. The conformation of the nearly parallel cyclo­penta­dienyl (Cp) rings [the dihedral angle between their planes is 2.7 (1)°] is almost halfway between eclipsed and staggered, and the rings are mutually twisted by about 19.4 (2)° (mean value). The mean lengths of the C—C bonds in the substituted and unsubstituted cyclo­penta­dienyl ring are 1.420 (2) and 1.406 (3) Å, respectively, and the Fe—C distances range from 2.029 (2) to 2.051 (2) Å. The phenyl and unsubstituted cyclo­penta­dienyl rings are involved in C—H⃛π interactions, with intermolecular H⃛centroid distances of 2.85 and 3.14 Å for C—H⃛π(Ph), and 2.88 Å for C—H⃛π(Cp). In two of these interactions, the C—H bond points towards one of the ring bonds rather than towards the ring centroid. In the crystal structure, the C—H⃛π interactions connect the mol­ecules into a three‐dimensional framework.     

Hydro­gen‐bonding patterns in cis‐4‐ammonio­cyclo­hexane­carboxyl­ate hemihydrate

In the title compound, C₇H₁₃NO₂·0.5H₂O, cis‐4‐amino­cyclo­hexane­carboxylic acid exists as a zwitterion and co‐crystallizes with water mol­ecules in a 2:1 amino acid–water ratio. The cyclo­hexane ring adopts a chair conformation, with the carboxyl­ate and ammonium groups in axial and equatorial positions, respectively. The basic motif in the crystal structure is a sandwich structure, formed by two amino acid units linked by head‐to‐tail hydrogen bonds. Hydro­gen bonds of the type N⁺—H⋯O—C—O⁻ link these motifs, forming helicoidally extended chains running along the c axis. The water molecule lies on a twofold axis and interacts with the chains by means of O—H⋯O hydrogen bonds.     

Caulerpin

The crystal structure of caulerpin (di­methyl 6,13‐di­hydro­dibenzo­[b,i]­phenazine‐5,12‐di­carboxyl­ate, C₂₄H₁₈N₂O₄), an indole alkaloid, reported in space group Cc with an acute β angle, has been redetermined in the correct space group, C2/c. The mol­ecule has twofold crystallographic symmetry and is composed of two essentially planar indole groups fused to an eight‐membered cyclo­octatetraene ring which adopts a boat conformation. The molecular dimensions are normal. The structure is stabilized by intermolecular and intramolecular interactions involving the indole N—H atom and carbonyl O atom [N?O 3.211 (4) and 2.836 (4) Å].     

17‐Oxo‐16‐(2‐pyridyl­methyl­ene)­androst‐5‐en‐3β‐ol monohydrate

The title compound, C₂₅H₃₁NO₂·H₂O, has the outer two six‐membered rings in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐membered ring adopts a 13,14‐half‐chair conformation. The pyridyl­methyl­ene moiety has an E configuration with respect to the carbonyl group at position 17. The structure is stabilized by intermolecular O—H?N and O—H?O hydrogen bonds.     

Ferrocene compounds. XXXVIII. Di­methyl ferrocene‐1,1′‐di­carboxyl­ate

In the title compound, [Fe(C₇H₇O₂)₂], the cyclo­penta­dienyl rings and the two attached methoxy­carbonyl groups, in an anti arrangement, form an extended π‐conjugated system. The Fe—C distances range from 2.035 (3) to 2.061 (3) Å and the average value of the C—C bond lengths in the two cyclo­penta­dienyl rings is 1.419 (5) Å. The rings are almost parallel to one another [1.0 (2)°] and are mutually twisted from an eclipsed conformation by only 1.8 (3)° (average value). The methoxy­carbonyl groups are twisted out of the plane of the cyclo­penta­dienyl rings by 6.5 (4) and 15.7 (4)°, respectively. The mol­ecules are joined into dimers by intermolecular C—H⃛O hydrogen bonds that form ten‐membered rings. The same types of hydrogen bonds form eight‐membered rings and infinite chains along the b axis.     

(1SR,2RS,5RS,6SR,8RS)‐7,7‐Dimethyltricyclo[6.2.1.01,6]undecane‐2,5,6‐triol: a supramolecular framework built from O—H⋯O hydrogen bonds

In the title compound, C₁₃H₂₂O₃, the asymmetric unit has two independent mol­ecules linked by a strong O—H?O hydrogen bond. The cyclo­hexane ring is trans fused to the cyclo­pentane ring bridged through an ethyl moiety. The hydroxyl groups act as donors as well as acceptors, resulting in an extensive two‐dimensional hydrogen‐bonded network in the (011) plane. Intermolecular O—H?O bonds between centrosymmetrically related mol­ecules form a four‐membered supramolecular assembly, leading to infinite chains parallel to the [01] direction, crosslinked in the [100] direction.     

Two isomers of 2,4‐di­benzyl‐8‐azabicyclo­[3.2.1]­octan‐3‐ol

The crystal structures of the title compounds, 2α,4α‐di­benzyl‐3α‐tropanol (2α,4α‐di­benzyl‐8‐methyl‐8‐aza­bi­cyclo­[3.2.1]­octan‐3α‐ol), C₂₂H₂₇NO, (I), and 2α,4α‐di­benzyl‐3β‐tropanol (2α,4α‐di­benzyl‐8‐methyl‐8‐aza­bi­cyclo­[3.2.1]­octan‐3β‐ol), C₂₂H₂₇NO, (II), show that both compounds have a piperidine ring in a chair conformation and a pyrrolidine ring in an envelope conformation. Isomer (I) is asymmetric, the benzyl groups having different orientations, whereas isomer (II) is mirror symmetric, and the N and O atoms, the C atom attached to the hydroxy group, and the methyl C atom attached to the N atom lie on the mirror plane. In the crystal structures of both (I) and (II), the mol­ecules are linked together by intermolecular O—H⋯N hydrogen bonds to form chains that run parallel to the a direction in (I) and parallel to b in (II).     

16‐[3‐Methoxy‐4‐(2‐piperidin‐1‐yl­ethoxy)­benzyl­idene]‐17‐oxoandrost‐5‐en‐3β‐yl acetate monohydrate

The title compound, C₃₆H₄₉NO₅·H₂O, has the outer two six‐membered rings of the steroid nucleus in chair conformations. The central ring B of the steroid nucleus is in an 8β,9α‐half‐chair conformation, while ring D of the steroid adopts a slightly distorted 13β,14α‐half‐chair conformation. The piperidine ring is in a chair conformation. The methoxy­benzyl­idene moiety has an E configuration with respect to the carbonyl group at position 17. Intermolecular O—H?O and O—H?N hydrogen bonds link the steroid and water mol­ecules into chains which run parallel to the b axis.     

7,8‐Dihydr­oxy‐4‐propyl‐1,2,3,4,4a,5,6,10b‐octa­hydro­benzo[f]quinolinium bromide monohydrate,a dopamine agonist

In the crystal structure of the title dopamine­rgic compound, C₁₆H₂₄NO₂⁺·Br⁻·H₂O, protonation occurs at the piperidine N atom. The piperidine ring adopts a chair conformation and the cyclo­hexene ring adopts a half‐chair conformation; together with the planar benzene ring, this results in a relatively planar shape for the whole mol­ecule. Classical hydrogen bonds (N—H⋯Br, O—H⋯Br and O—H⋯O) produce an infinite three‐dimensional network. Hydrogen bonds between water ­mol­ecules and Br⁻ anions create centrosymmetric rings throughout the crystal structure. Structural comparison of the mol­ecule with the ergoline dopamine agonist pergolide shows that it is the hydrogen‐bond‐forming hydr­oxy or imino group that is necessary for dopamine­rgic activity, rather than the presence of a phenyl or a pyrrole ring per se.