The antifolate trimetrexate: ­observation of the enzyme‐binding conformation

The crystal structure of the title compound contains four 2,4‐di­amino‐5‐methyl‐6‐[(3,4,5‐tri­methoxy­anilino)­methyl]­quin­az­oline mol­ecules, two di­methyl sulfoxide mol­ecules and three water mol­ecules in the asymmetric unit, i.e. 4C₁₉H₂₃N₅O₃·2C₂H₆OS·3H₂O. All four quinazoline mol­ecules adopt trans,gauche conformations. An extensive hydrogen‐bond network involving N?N base‐pairing interactions, as well as the di­methyl sulfoxide and water mol­ecules, stabilizes the crystal structure.     

A mixed crystal of imperatorin and phellopterin,with C—H...O,C—H...π and π–π interactions

The crystal structure of 9‐(3‐methyl­but‐2‐enyl­oxy)­‐7H‐furo­[3,2‐g]­chro­men‐7‐one–4‐methoxy‐9‐(3‐methyl­but‐2‐enyl­oxy)‐7H‐­furo­[3,2‐g]­chromen‐7‐one (0.926/0.074), 0.926C₁₆H₁₄O₄·0.074C₁₇H₁₆O₅, is characterized by two independent imperatorin mol­ecules in the asymmetric unit, which exhibit different side‐chain conformations. A small amount of phellopterin overlaps with one of the two imperatorin mol­ecules. The supramol­ecular structure is supported by C—H...O, C—H...π and π–π interactions.     

Trityl losartan

The title compound (systematic name: {2‐butyl‐4‐chloro‐1‐[2′‐(2‐trityl‐2H‐tetrazol‐5‐yl)­bi­phenyl‐4‐yl­methyl]‐1H‐imidazol‐5‐yl}­methanol), C₄₁H₃₇ClN₆O, crystallizes in the centrosymmetric space group P with two independent mol­ecules in the asymmetric unit. These mol­ecules differ significantly only in the relative orientations of the rings in the bi­phenylyl­tetrazole moieties. One of the mol­ecules shows disorder for three C atoms in the n‐butyl group. Hydro­gen bonds link the mol­ecules in an infinite chain along the a axis.     

Gabapentin and gabapentin monohydrate

Gabapentin [1‐(amino­methyl)­cyclo­hexane­acetic acid, C₉H₁₇NO₂] is a zwitterion in the solid state. Its crystal structure involves extensive hydrogen bonding between the NH₃⁺ and COO^? groups of neighboring mol­ecules. The structure of gabapentin monohydrate [1‐(amino­methyl)­cyclo­hexane­acetic acid monohydrate, C₉H₁₇NO₂·H₂O] also involves such hydrogen bonding and, in addition, has a hydrogen‐bonding network comprising the water mol­ecules and both the NH₃⁺ and COO^? groups.     

(E)‐(4‐Hydroxyphenyl)(4‐nitrophenyl)diazene, (E)‐(4‐methoxyphenyl)(4‐nitrophenyl)diazene and (E)‐[4‐(6‐bromohexyloxy)phenyl](4‐cyanophenyl)diazene

Syntheses and X‐ray structural investigations have been carried out for (E)‐(4‐hydroxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₂H₉N₃O₃, (Ia), (E)‐(4‐methoxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₃H₁₁N₃O₃, (IIIa), and (E)‐[4‐(6‐bromo­hexyl­oxy)­phenyl](4‐cyano­phenyl)­diazene, C₁₉H₂₀BrN₃O, (IIIc). In all of these compounds, the mol­ecules are almost planar and the azo­benzene core has a trans geometry. Compound (Ia) contains four and compound (IIIc) contains two independent mol­ecules in the asymmetric unit, both in space group P (No. 2). In compound (Ia), the independent mol­ecules are almost identical, whereas in crystal (IIIc), the two independent mol­ecules differ significantly due to different conformations of the alkyl tails. In the crystals of (Ia) and (IIIa), the mol­ecules are arranged in almost planar sheets. In the crystal of (IIIc), the mol­ecules are packed with a marked separation of the azo­benzene cores and alkyl tails, which is common for the solid crystalline precursors of mesogens.     

(±)‐2‐Oxocyclohexanepropionic acid: dual conformational selection and hydrogen bonding in a δ‐keto acid,and a two‐phase technique for crystallizing acids by contact with aqueous solutions of their salts

The asymmetric unit of the title compound, C₉H₁₄O₃, consists of two mol­ecules having conformations that differ by 121.7 (4)° in their rotation about the equatorial substituent bond, so that the side chain extends away from the ring in different directions in the two species. The hydrogen‐bonding mode is acid‐to‐acid dimerization. However, despite the centrosymmetric space group (P), the dimers are asymmetric, formed by pairing mol­ecules of identical chirality but differing conformational type [O⋯O = 2.681 (2) and 2.654 (2) Å, and O—H⋯O = 175 (3) and 176 (3)°]. Two intermolecular C—H⋯O=C close contacts exist, involving the ketone group of one of the mol­ecules. A two‐phase technique is described for slow reforming of crystals of a water‐insoluble acid by contact with an aqueous solution of its water‐soluble salt.     

Four tri­fluoro­methyl­nitro­benzene analogues

The crystal structures of four tri­fluoro­methyl­nitro­benzene analogues (CF₃)C₆H₃(NO₂)[C₄H₈N₂]R (where C₄H₈N₂ is piperazinyl and R is ethyl carboxyl­ate, CO₂C₂H₅, or phenyl, C₆H₅), have been determined, and their conformations and packing arrangements are compared. The four compounds are ethyl 4‐[4‐nitro‐2‐(tri­fluoro­methyl)­phenyl]­piperazine‐1‐car­boxyl­ate, (I), and ethyl 4‐[2‐nitro‐4‐(tri­fluoro­methyl)­phen­yl]piper­azine‐1‐carboxyl­ate, (II), both C₁₄H₁₆F₃N₃O₄, and 1‐­[4‐nitro‐2‐(tri­fluoro­methyl)­phenyl]‐4‐phenyl­piperazine, (III), and 1‐[2‐nitro‐4‐(tri­fluoro­methyl)­phenyl]‐4‐phenyl­piperazine, (IV), both C₁₇H₁₆F₃N₃O₂. All mol­ecules adopt a rod‐like conformation, while the asymmetric units of (II) and (IV) contain two unique mol­ecules that pack as monodirectional pairs. All mol­ecules pack with C—H⋯O/F close contacts to all but one of the O atoms and to five of the 18 F atoms.     

N‐(3H‐Thia­zol‐2‐yl­idene)­nitr­amine and N‐methyl‐N‐(thia­zol‐2‐yl)­nitr­amine

The geometries of the thia­zole ring and the nitr­amino groups in N‐(3H‐thia­zol‐2‐yl­idene)­nitr­amine, C₃H₃N₃O₂S, (I), and N‐­methyl‐N‐(thia­zol‐2‐yl)­nitr­amine, C₄H₅N₃O₂S, (II), are very similar. The nitr­amine group in (II) is planar and twisted along the C—N bond with respect to the thia­zole ring. In both structures, the asymmetric unit includes two practically equal mol­ecules. In (I), the mol­ecules are arranged in layers connected to each other by N—H⋯N and much weaker C—H⋯O hydrogen bonds. In the crystal structure of (II), the mol­ecules are arranged in layers bound to each other by both weak C—H⋯O hydrogen bonds and S⋯O dipolar interactions.     

Two modifications of l‐alanyl‐l‐tyrosyl‐l‐alanine with different solvent mol­ecules in the crystal lattice

The low‐temperature crystal and mol­ecular structure analyses of two modifications of l ‐alanyl‐l ‐tyrosyl‐l ‐alanine with water, C₁₅H₂₁N₃O₅·2.63H₂O [(I), at 9 K], and ethanol, C₁₅H₂₁N₃O₅·C₂H₅O [(II), at 20 K], solvent mol­ecules in the crystal lattice show that the overall conformations of both modifications of the title tripeptide are practically the same. Moreover, despite the presence of different solvent mol­ecules in the crystal lattice, the specific inter­molecular inter­actions characteristic for individual tripeptide mol­ecules of (I) and (II) are conserved. The crystal packing of the two modifications of Ala‐Tyr‐Ala differ from each other only in the solvent region. The tight arrangements of tripeptide mol­ecules seem to be responsible for similar displacement parameters for all non‐H atoms, despite the different distances from the mol­ecular centre of mass. Comparison of the displacement parameters between the room‐ and low‐temperature structures shows that an average U_eq value decrease of about 80% takes place at 9 K [for (I)] and 20 K [for (II)] with respect to room temperature.     

Solvates of zafirlukast

The crystal structures of three solvates of zafirlukast [systematic name: cyclopentyl N‐{1‐methyl‐3‐[2‐methyl‐4‐(o‐tolylsulfonylaminocarbonyl)benzyl]‐1H‐indol‐5‐yl}carbamate], viz. the monohydrate, C₃₁H₃₃N₃O₆S·H₂O, (I), the methanol solvate, C₃₁H₃₃N₃O₆S·CH₃OH, (II), and the ethanol solvate, C₃₁H₃₃N₃O₆S·C₂H₅OH, (III), have been determined by single‐crystal X‐ray diffraction analysis. All three compounds crystallize in the monoclinic crystal system. Zafirlukast adopts a similar Z‐shaped conformation in all three solvates. The methanol and ethanol solvates are isostructural. The packing of the zafirlukast mol­ecules in all three crystal structures is similar and is expressed by hydrogen‐bonded mol­ecules that are related by translation, along (101) in (I) and along the b axis in (II) and (III). The methanol and ethanol solvent mol­ecules are hydrogen bonded to two mol­ecules of zafirlukast. The water mol­ecule, on the other hand, acts as a connector via hydrogen bonds between three mol­ecules of zafirlukast. The solvent mol­ecules are not released at temperatures below the melting points of the solvates.     

(−)‐3,7‐Dioxo‐5β‐cholanic acid: dual hydrogen‐bonding modes in a diketonic bile‐acid derivative

The asymmetric unit of the title compound, C₂₄H₃₆O₄, contains three mol­ecules, all differing in their side‐chain conformations and all linked by hydrogen bonding confined entirely within a three‐mol­ecule block. One connection is of the acid‐to‐ketone type [O⋯O = 2.7055 (19) Å and O—H⋯O = 180°] and the other involves carboxyl pairing [O⋯O = 2.6485 (18) and 2.6598 (18) Å, and O—H⋯O = 168 and 174°]. Numerous inter­molecular C—H⋯O close contacts connect neighbouring mol­ecules.     

Stigmasterol hemihydrate

The title compound, stigmasta‐5,22‐dien‐3β‐ol hemihydrate, C₂₉H₄₈O·0.5H₂O, previously thought to be the monohydrate, has two sterol mol­ecules and one water mol­ecule in the asymmetric unit. In both sterol mol­ecules, the methyl group of the ethyl substituent at the end of the hydro­carbon chain is disordered over two sites. The OH group of mol­ecule A donates a hydrogen bond to a water mol­ecule and accepts a hydrogen bond from the OH group of mol­ecule B. The OH group of mol­ecule B accepts two hydrogen bonds from water mol­ecules.     

The solid dihydrate of N,N‐di­methyl‐n‐tetra­decyl­amine oxide

Crystalline N,N‐di­methyl‐n‐tetra­decyl­amine oxide has been prepared by reaction of liquid N,N‐di­methyl‐n‐tetra­decyl­amine with 70% H₂O₂ in the presence of CO₂ as catalyst. The resulting soft low‐melting solid was crystallized as the dihydrate, viz. C₁₆H₃₅NO·2H₂O. The extended hydro­carbon chains pack in a parallel fashion, with the N‐oxide ends of the mol­ecules forming hydrogen bonds with the water mol­ecules in hydro­philic layers. The N—O distance is 1.411 (3) Å.     

4,5‐Di­azafluoren‐9‐one benzoyl­hydrazone monohydrate

The title compound, C₁₈H₁₂N₄O·H₂O, adopts the keto tautomeric form and the azomethine C=N double bond is in the E configuration. The dihedral angle between the planes of the di­aza­fluorene moiety and the phenyl ring is 11.3 (1)°. In the solid state, the mol­ecules form infinite chain‐like structures via O—H?N hydrogen bonds involving the water mol­ecules and di­aza­fluorene moieties.     

trans‐4‐Bromo‐ONN‐azoxy­benzene at 100 K

The crystal structure of the α isomer of trans‐4‐bromo­azoxy­benzene [systematic name: trans‐1‐(bromophenyl)‐2‐phenyl­diazene 2‐oxide], C₁₂H₉BrN₂O, has been determined by X‐ray dif­frac­tion. The geometries of the two mol­ecules in the asymmetric unit are slightly different and are within ∼0.02 Å for bond lengths, ∼2° for angles and ∼3° for torsion angles. The azoxy bridges in both mol­ecules have the typical geometry observed for trans‐azoxy­benzenes. The crystal network contains two types of planar mol­ecules arranged in columns. The torsion angles along the Ar—N bonds are only 7 (2)°, on either side of the azoxy group.     

(–)‐Dioxosantadienic acid: hydrogen‐bonding patterns in a bicyclic sesquiterpenoid keto acid and its mono­hydrate

The an­hydrous form, (I), of the title compound, (?)‐2‐(1,2,3,4,4a,7‐hexa­hydro‐4a,8‐di­methyl‐1,7‐dioxo‐2‐naphthyl)­propionic acid, C₁₅H₁₈O₄, derived from a naturally occurring sesquiterpenoid, has two mol­ecules in the asymmetric unit, (I) and (I′), differing in the conformations of the saturated ring and the carboxyl group. The compound aggregates as carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.776 (3) and 2.775 (3) Å]. Two crystallographically independent sets of single‐strand hydrogen‐bonding helices with opposite end‐to‐end orientation pass through the cell in the b direction, one consisting exclusively of mol­ecules of (I) and the other entirely of (I′). Three C—H?O=C close contacts are found in (I). The monohydrate, C₁₅H₁₈O₄·H₂O, (II), with two mol­ecules of (I) plus two water mol­ecules in its asymmetric unit, forms a complex three‐dimensional hydrogen‐bonding network including acid‐to‐water, water‐to‐acid, water‐to‐ketone, water‐to‐water and acid‐to‐acid hydrogen bonds, plus three C—H?O=C close contacts. In both (I) and (II), only the ketone remote from the acid is involved in hydrogen bonding.     

2‐Hydroxy‐3‐(3‐oxobut­yl)naphthalene‐1,4‐dione

The title compound, C₁₄H₁₂O₄, forms crystals which appear monoclinic but are actually twinned triclinic. The asymmetric unit consists of two similar mol­ecules, which differ only in the conformation of the 3‐oxobutyl side chain. The mol­ecular conformation is characterized by an intra­molecular O—H⋯O hydrogen bond between the hydroxy group and the adjacent carbonyl O atom. The crystal structure is stabilized by O—H⋯O hydrogen bonds connecting the mol­ecules into zigzag chains running along the b axis.     

The new chiral ligand 3‐ethoxy‐4‐[(1R,2S)‐(2‐hydroxy‐1,2‐di­phenyl­ethyl)­amino]‐3‐cyclo­butene‐1,2‐dione

The asymmetric unit of C₂₀H₁₉NO₄ contains two mol­ecules with slightly different conformations. In the crystal, the mol­ecules are linked by O—H?O and N—H?O hydrogen bonds [O?O 2.764 (3) and 2.811 (3) Å; N?O 2.907 (3) and 2.968 (3) Å] to form a two‐dimensional network.     

4‐(4‐Hydro­xy­benzyl­idene­amino)‐4H‐1,2,4‐triazole hemihydrate

In the title compound, 4‐(4H‐1,2,4‐triazol‐4‐yl­imino­methyl)­phenol hemi­hydrate, C₉H₈N₄O·0.5H₂O or (I)·0.5H₂O, mol­ecules of (I) are arranged as layers running along the b axis through intermolecular O—H?N and C—H?O hydrogen bonds. These layers are stabilized by hydrogen‐bonded water mol­ecules to form three‐dimensional networks.     

Moxifloxacinium chloride–water–methanol (2/1/1), a novel anti­bacterial agent

Moxifloxacin, a novel fluoro­quinolone with a broad spectrum of anti­bacterial activity, is available as the solvated monohydro­chloride salt 7‐[(S,S)‐2‐aza‐8‐azoniabicyclo­[4.3.0]non‐8‐yl]‐1‐cyclo­propyl‐6‐fluoro‐8‐meth­oxy‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylic acid chloride–water–methanol (2/1/1), C₂₁H₂₅FN₃O₄⁺·Cl⁻·0.5H₂O·0.5CH₃OH. The asymmetric unit contains two cations, two chloride ions, a mol­ecule of water and one methanol mol­ecule. The two cations adopt conformations that differ by an almost 180° rotation with respect to the piperidinopyrrolidine side chain. The cyclo­propyl ring and the meth­oxy group are not coplanar with the quinoline ring system. The carboxylic acid function, the protonated terminal piperidyl N atom, the water mol­ecule, the chloride ion and the methanol mol­ecule participate in O—H⋯O, O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonding, linking the mol­ecules into extended two‐dimensional networks.