Isomeric pyrazolo­[3,4-d]­pyrimidine-based mol­ecules: disappearance of dimerization due to interchanged substitutions

In 5-benzyl-1,7-di­methyl-4,5,6,7-tetra­hydro-1H-pyrazolo­[3,4-d]­pyrimidine-4,6-dione, C₁₄H₁₄N₄O₂, which crystallizes in space group P, weak intermolecular C—H⋯O hydrogen bonds generate dimers. The isomeric compound 1-benzyl-5,7-di­methyl-4,5,6,7-tetra­hydro-1H-pyrazolo­[3,4-d]­pyrimidine-4,6-dione, C₁₄H₁₄N₄O₂, crystallizes in space group P2₁/n, and shows no such dimerization. Instead, it exhibits C—H⋯π interactions with the phenyl ring. In both structures, the mol­ecules are linked by aromatic π–π-stacking interactions.     

Marine sterols—II : Asterosterol,a new C26 sterol from Asterias amurensis lütken

Asterosterol, a new marine C₂₆ sterol, was isolated from the asteroid, A. amurensis, and its structure was characterized as 22-trans-24-nor-5α-cholesta-7,22-dien-3β-ol (1). Episterol (9), 22-trans-(24R)-24-methylcholesta-7,22-dien-3β-ol (stellasterol, 3) and 22-trans-cholesta-7,22-dien-3β-ol (7) were also isolated and their structures were confirmed.     

Aquabis(3,5-dimethyl-1H-pyrazole-κN2)(malonato-κ2O,O′)copper(II) ­dihydrate

In the neutral title complex, [Cu(C₃H₂O₄)(C₅H₈N₂)₂(H₂O)]·2H₂O or [Cu(mal)(dmp)₂(H₂O)]·2H₂O (mal is malon­ate and dmp is 3,5-di­methyl-1H-pyrazole), the Cu^II ion, in a slightly distorted square-pyramidal geometry, is coordinated by two O atoms of the bidentate malonate, the O atom of the water ligand and two N atoms from the two 3,5-di­methyl­pyrazole ligands. The mean Cu—N bond length is 2.007 (6) Å, longer than the Cu—O_mal bonds [1.950 (5) Å]. The apical position is occupied by a relatively strongly coordinated water mol­ecule [Cu—O_water 2.288 (5) Å]. The crystal structure is characterized by the layer motif of a hydrogen-bonded network.     

Conformational isomers of neutral trans-di­nitro­cobalt(III) complexes

The reaction of Co(acac)₃ with N-(2-amino­ethyl)-1,3-propane­di­amine in the presence of NaNO₂ results in the preparation of an unexpected di­nitro­cobalt(III) compound, (11-amino-4-methyl-5,8-di­aza­undeca-2,4-dien-2-olato-κ⁴­N^5,8,11,O)-di­nitrocobalt(III), [Co(C₁₀H₂₀N₃O)(NO₂)₂], containing the tetra­dentate anion of 11-amino-4-methyl-5,8-diazaundeca-2,4-dien-­2-ol. Two isomers of the compound were obtained by recrystallization of the crude product. In one isomer, the two trans nitro groups are staggered, and in the other they are eclipsed.     

Intermolecular interactions in two (ferrocenylmethyl)benzimidazoles incorporating the 4-MeOC6H4 and 3,4-(MeO)2C6H3 groups: analysis of MeO—C—C distortions from ideal 120° geometry

The title compounds, 1-ferrocenyl­methyl-2-(4-methoxy­phenyl)-1H-benz­imidazole, [Fe(C₅H₅)(C₂₀H₁₇N₂O)], (I), and 2-(3,4-di­methoxy­phenyl)-1-ferrocenyl­methyl-1H-benz­imid­az­ole, [Fe(C₅H₅)(C₂₁H₁₉N₂O₂)], (II), are model electroactive compounds for anion sensor and antimalarial applications. Distortions from the ideal 120° angle about the MeO—C—C groups are evident, with angles of 115.1 (2) and 125.0 (2)° in (I), and 115.9 (2) and 124.6 (2)°, and 115.7 (2) and 125.1 (2)° in (II). The main intermolecular hydrogen bonds in (I) comprise C—H⋯N and C—H⋯π(C₅H₅) interactions, while in (II), only weak C—H⋯π(imidazole) and C—H⋯π(arene) interactions are present.     

Some Diels–Alder adducts of 6-vinyl-1-oxa-4-thiaspiro[4.5]dec-6-ene

6-Vinyl-1-oxa-4-thia­spiro­[4.5]­dec-6-ene has been reacted with dienophiles, such as N-phenyl­male­imide (NPM), N-methyl­triazoline-2,5-dione (MTAD) and di­methyl­acetyl­ene di­carboxyl­ate (DMAD), to assess the 1,3-diastereofacial selection caused by the acetal function. In each case, a mixture of two diastereoisomers was produced. The crystal structures of the products of the addition of NPM and MTAD syn to the acetal oxy­gen, 2-phenyl-2,3,3a,4,5,5a,6,7,8,9,9a,9b-dodeca­hydro-1H-benz­[e]­iso­indole-6-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₂₀H₂₁NO₃S, (IIa), and 2-methyl-5,7,8,9,10,10a-hexa­hydro-1H-1,2,4-triazolo­[1,2-a]­cinnoline-7-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₁₃H₁₇N₃O₃S, (IIIa), respectively, and the product of the addition of DMAD syn to the acetal sulfur, di­methyl 1,2,3,4,4a,7-hexa­hydro­naphthalene-1-spiro-2′-[1′,3′]­oxa­thiol­ane-5,6-di­carboxyl­ate, C₁₆H₂₀O₅S, (IVb), have been determined. All three structures are composed of independent mol­ecules separated by normal van der Waals distances. The 1-oxa-4-thia heterocyclic ring has an envelope conformation in the three structures and the S—Csp³ bond distances differ significantly from each other, as observed in comparable structures; the remaining molecular dimensions are as expected.     

Two (E,E)- and (Z,E)-thiazol-5-ylpenta-2,4-dienones

In order to characterize the structural elements that might play a role in non-covalent DNA binding by the antitumor antibiotic leinamycin, we have solved the crystal structures of the two leinamycin analogs, methyl (R)-5-{2-[1-(tert-butoxy­carbonyl­amino)­ethyl]­thia­zol-4-yl}penta-(E,E)-2,4-dienoate, C₁₆H₂₂N₂O₄S, (II), and 2-methyl-8-oxa-16-thia-3,17-di­aza­bicyclo­[12.2.1]­heptadeca-(Z,E)-1(17),10,12,14-tetraene-4,9-di­one, C₁₄H₁₆N₂O₃S, (III). The penta-2,4-dienone moiety in both of these analogs adopts a conformation close to planarity, with the thia­zole ring twisted out of the plane by 12.9 (2)° in (II) and by 21.4 (4)° in (III).     

Naturally occurring 1,2,8-trimethoxyxanthone and biphenyl ether intermediates leading to 1,2-dimethoxyxanthone

In order to study structure–activity relationships, a series of mono-, di- and trioxy­genated xanthones has been synthesized and the structures of methyl 2-(3,4-di­methoxy­phenoxy)­benzoate, C₁₆H₁₆O₅, 2-(3,4-di­methoxy­phenoxy)­benzoic acid, C₁₅H₁₄O₅, 1,2-di­methoxy-9H-xanthen-9-one, C₁₅H₁₂O₄, and 1,2,8-tri­methoxy-9H-xanthen-9-one, C₁₆H₁₄O₅, have been determined. The first two compounds both assume skew conformations, the dihedral angles between the two phenyl rings being 80.04 (8) and 83.0 (1)°, respectively. The latter two compounds are essentially planar and their methoxy substituents assume orientations consistent with minimum steric interactions.     

Steroid alcohols from the ascidianHalocynthia aurantium

The total sterols have been isolated fromHalocynthia aurantium by column chromatography on silica gel. The following steroid alcohols have been identified in it with the aid of GLC, GLC-MS, and¹H NMR: 5α-cholestan-3β-ol, 24ξ-methylcholestan-3β-ol, 24ξ-ethylcholestan-3β-ol, 4ξ-methyl-24ξ-ethyl-5α-cholestan-3β-ol, cholest-5-en-3β-ol, 24ξ-methylcholest-5-en-3β-ol, 24ξ-ethylcholes-5-en-3β-ol, 5α-cholest-22-en-3β-ol, 24-nor-5α-cholest-22-en-3β-ol, cholesta-5,22-dien-3β-ol, 24ξ-methylcholesta-5,22-dien-3β-ol, 24-norcholesta-5,22-dien-3β-ol, 24-ethylcholesta-5,24(28)-dien-3β-ol, and 24-methylcholesta-5,24(28)-dien-3β-ol.     

A nitronyl nitro­xide complex of ­nickel(II) with nitrate as a ligand

The complex cation in [4,5-di­hydro-4,4,5,5-tetra­methyl-2-(2-pyridyl-κN)­imidazol-1-oxyl 3-oxide-κO³](nitrato-κ²O,O′)(N,N,N′,N′-tetra­methyl-1,2-ethanedi­am­ine-κ²N,N′)­nickel(II) hexafluorophosphate dichloromethane solvate, [Ni(NO₃)(C₆H₁₆N₂)(C₁₂H₁₆N₃O₂)]PF₆·CH₂Cl₂, is the first example of a nitro­nyl nitro­xide complex of a transition metal ion having d electrons in which nitrate is coordinated as a bidentate ligand. Owing to the smaller steric requirement of NO₃⁻, the Ni—­O(nitro­xide) bond length [2.014 (2) Å] is remarkably shorter than that in the corresponding ­β-­diketonate complexes [2.052 (4)–2.056 (2) Å].     

Polyether antibiotic CP44,161

The crystal structure of antibiotic CP44,161, 6-(7-{2-ethyl-2-[5-(1-hydroxy­methyl)-5-methyl-2,3,4,5-tetra­hydro-2-furyl]-4,10,-­12-tri­methyl-1,6,8-trioxadi­spiro­[4.1.5.3]­pentadec-13-en-9-yl}-4-hydroxy-3,5-di­methyl-6-oxononyl)-2-hydroxy-3-methyl­benzoic acid monohydrate, C₄₃H₆₆O₁₀·H₂O, has been determined by X-ray crystallography. The mol­ecule adopts a cyclic conformation, with a centrally located water mol­ecule contributing to the stability of the conformation through hydrogen-bonding interactions.     

Diels–Alder adducts of medium-ring carbocyclic dienes prepared by rearrangement of catalytically generated cyclic oxonium ylides

The novel bicyclic and tricyclic systems di­methyl (4aS*,6S*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexa­hydro-2H-benzo­cyclo­hept­ene-3,4-di­carboxyl­ate, C₁₆H₂₀O₆, (I), di­methyl (4aS*,6R*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexa­hydro-2H-benzo­cyclo­hept­ene-3,4-di­carboxyl­ate, C₁₆H₂₀O₆, (II), (3aS*,9R*,10aS*,10bR*)-9-methoxy-2-oxa-1,3a,4,6,7,8,9,10,10a,10b-deca­hydro-3H-cyclo­hepta­[e]­indene-1,3,8-trione, C₁₄H₁₆O₅, (III), and (1S*,2R*,9S*,10aR*)-9-methoxy-8-oxo-1,2,3,5,6,7,8,9,10,10a-deca­hydrobenzo­cyclo­octene-1,2-di­carboxyl­ic acid, C₁₅H₂₀O₆, (IV), have been crystallographically characterized, allowing the determination of the relative configuration of the stereogenic centres. The poor quality of the di­carboxyl­ic acid crystals necessitated the use of synchrotron radiation.     

Pyrazolidine-3,5-dione angiotensin-II receptor antagonists

The crystal structures of three angiotensin-II receptor antagonists involving different spacer groups (CO, CONH and NHCO) between the aryl rings are presented, namely 2-{4-[(3-butyl-1,4-dioxo-2,3-di­aza­spiro­[4.4]­non-2-yl)­methyl]­benzoyl}benzoic acid, C₂₆H₂₈N₂O₅, (I), 2-{4-[(3-butyl-1,4-dioxo-2,3-di­aza­spiro­[4.4]­non-2-yl)­methyl]­benz­amido}benzoic acid, C₂₆H₂₉N₃O₅, (II), and 2-{4-[(3-butyl-1,4-dioxo-2,3-di­azaspiro­[4.4]­non-2-yl)­methyl]­anilino­carbonyl}benzoic acid monohydrate, C₂₆H₂₉N₃O₅·H₂O, (III). The aryl rings of (II) are almost coplanar, in contrast with compounds (I) and (III). The conformation of (II) is induced by an intramolecular N—H⋯O hydrogen bond between the amide and carboxyl­ic acid groups.     

KNI-272, a highly selective and potent peptidic HIV protease inhibitor

Kynostatin {KNI-272; systematic name: 3-[3-benzyl-2-hydroxy-9-(isoquinolin-5-yl­oxy)-6-methyl­sulfanyl­methyl-5,8-dioxo-4,7-di­aza­nonanoyl]-N-tert-butyl-1,3-thia­zolane-4-carbox­amide}, a highly selective and potent HIV protease inhibitor containing allo­phenyl­norstatin [(2S,3S)-3-amino-2-hydroxy-4-phenyl­butyric acid], has been crystallized as the hydrate, C₃₃H₄₁N₅O₆S₂·0.803H₂O, from aqueous hexyl­ene glycol. The observed disorder of the phenyl group in the structure is related to the mode of hydration. The backbone conformation of the mol­ecule is twisted and the overall conformation of the free inhibitor is similar to that observed in its complex with HIV protease.     

Hydro­gen bonding in two tetracyclic indole alkaloids

3-Acetyl-1,6,7,12b-tetra­hydro­indolo­[2,3-a]­quinolizin-2(12H)-one, C₁₇H₁₆N₂O₂, consists of two symmetry-independent mol­ecules and each forms a layered structure stabilized by N—H⃛O and C—H⃛O hydrogen bonds. In 3-acetyl-6,7-di­hydro­indolo­[2,3-a]­quinolizin-4(12H)-one monohydrate, C₁₇H₁₄N₂O₂·H₂O, the structure is stabilized by O—H⃛O, N—H⃛O and C—H⃛O hydrogen bonds, with the ordered water mol­ecule playing a crucial role in the self-assembly. Contribution from the weak interactions to the strong hydrogen-bonded network is a common feature in both structures.     

Metabolic pathways of dithiocar­bamates from laboratory powder diffraction data

In order to correlate the reactivity and molecular structures of di­thio­carbamates, the crystal structures of 6-di­methyl­amino-5-nitro­pyrimidin-4-yl N,N-diethyl­di­thio­carbamate, C₁₁H₁₇N₅O₂S₂, (Ia), and 6-methyl­amino-5-nitro­pyrimidin-4-yl N,N-diethyl­di­thio­carbamate, C₁₀H₁₅N₅O₂S₂, (Ib), and of the product of thermolysis of (Ib), namely 4-diethyl­amino-6-methyl­amino-5-nitro­pyrimidinium chloride monohydrate, C₉H₁₆N₅O₂⁺·Cl⁻·H₂O, (II), have been determined from X-ray laboratory powder diffraction data. Conformational preferences in (Ia) and (Ib) were studied on the density functional theory (DFT) level. Deviation of the reaction centre of the mol­ecule from planarity and breakage of the secondary S⃛O contact cause switching between two alternative pathways of thermolysis.     

A dinuclear pyrazolato-N:N′-bridged dinickel(II) complex of 1,3-bis(5-chlorosalicylideneamino)propan-2-ol

The title compound, μ-[1,3-bis(5-chloro-2-oxidobenzyl­idene­amino)­propan-2-olato(3−)]-O,N,O′:O′,N′,O′′-μ-(3,5-di­methyl­pyrazolato)-N:N′-dinickel(II), [Ni₂(C₁₇H₁₃Cl₂N₂O₃)(C₅H₇N₂)], has crystallographic mirror symmetry. The Ni atoms in the dinuclear structure are linked symmetrically by the N atoms of the 3,5-di­methyl­pyrazole group and by the alkoxo O atom. Each Ni^II ion is coordinated by two N atoms and two O atoms, forming a square plane with trans-N₂O₂ geometry.     

Chloro(2,9-dimethyl-1,10-phenanthroline-N,N′)(isoquinoline-1-carboxylato-O,N)copper(II)

The asymmetric unit of the title compound, [CuCl(C₁₀H₆NO₂)(C₁₄H₁₂N₂)], contains two monomeric copper mol­ecules, A and B. Each Cu atom is coordinated to one 2,9-di­methyl-1,10-phenanthroline (neocuproine) ligand via both N atoms, to one iso­quinoline-1-carboxyl­ate anion (IQC⁻) via the N and one O atom, and to one Cl⁻ anion. The environment of the Cu atom is approximately square pyramidal, with the apical position occupied by an N atom of neocuproine. In mol­ecule A, the Cu atom is 0.301 (1) Å above the basal plane; this distance is 0.316 (1) Å in mol­ecule B. The crystal packing is characterized by several hydrogen bonds.     

Two thia­zolino­[2,3-a]­iso­quinolinone S-oxides

The structures of two racemic thia­zolino­[2,3-a]­isoquinolinone S-oxides, i.e. 8,9-di­methoxy-2,3,5,6-tetra­hydro-10bH-thia­zolo­[2,3-a]­isoquinolin-3-one 1-oxide [C₁₃H₁₅NO₄S, (IIa)] and 8,9-di­methoxy-10b-methyl-2,3,5,6-tetra­hydro-10bH-thia­zolo­[2,3-a]­isoquinolin-3-one 1-oxide [C₁₄H₁₇NO₄S, (IIb)], are described. The thia­zolinone ring in (IIa) exists in an envelope conformation, while in (IIb), it assumes a half-chair conformation. In (IIa) and (IIb), the six-membered heterocyclic ring adopts an envelope conformation. The O atom at sulfur is oriented in a pseudo-axial position, whereas the H atom in (IIa) and the methyl group in (IIb), linked to the stereogenic C centre, occupy a bisectional position with respect to the partially saturated pyridine ring and a pseudo-axial position with respect to the thia­zolinone ring. In both structures, the S=O group and the substituent at the stereogenic C centre are trans with respect to one another. Intermolecular C—H⋯O hydrogen bonds are observed in the crystal lattice of (IIa) and (IIb).     

A one-dimensional zigzag coordination polymer: catena-poly­[[di­aqua­pyridine­nickel(II)]-μ-pyridine-2,3-di­carboxyl­ato-κ3N,O2:O3]

The asymmetric unit of the title one-dimensional coordination polymer, [Ni(C₇H₃NO₄)(C₅H₅N)(H₂O)₂]_n, contains a quino­linate dianion, a nickel(II) ion, two water mol­ecules and a pyridine mol­ecule. The pyridine-2,3-di­carboxyl­ate (quino­linate) ligands connect the nickel(II) ions in a head-to-tail fashion, resulting in the formation of a one-dimensional zigzag chain. Adjacent chains form pairs via an extensive network of hydrogen-bonding interactions. A weak C—H...O intermolecular hydrogen bond links neighboring pairs of chains, thus generating two-dimensional double-sheet layers that are stabilized viaπ–π-stacking interactions between adjacent quinolinate pyridyl rings.