A stacked pyrazolo­[3,4‐d]­pyrimidine‐based flexible mol­ecule: the effect on stacking of a bulky iso­propyl group in comparison with a methyl/ethyl group

In the crystal structure of 1,3‐bis(4,6‐diiso­propyl­sulfanyl‐1H‐pyrazolo­[3,4‐d]­pyrimidin‐1‐yl)­propane, C₂₅H₃₆N₈S₄, the pairs of pyrazolo­[3,4‐d]­pyrimidine rings in the mol­ecule stack as a result of intramolecular π–π interactions between the heterocyclic rings. The crystal packing also exhibits an intermolecular C—H...π interaction between one methyl group of an iso­propyl group and a pyrazolo­[3,4‐d]­pyrimidine ring.     

A stacked pyrazolo[3,4‐d]pyrimidine‐based flexible molecule: the effect of a bulky benzyl group on intermolecular stacking in comparison with methyl and ethyl groups

In the crystal structure of 1,1′‐(1,3‐propane­diyl)­bis(5‐benzyl‐6‐methyl­sulfanyl‐4,5‐di­hydro‐1H‐pyrazolo­[3,4‐d]­pyrimidin‐4‐one), C₂₉H₂₈N₈O₂S₂, the pairs of pyrazolo­[3,4‐d]­pyrimidine rings stack as a result of intramolecular π–π interactions between the heterocyclic rings. The folded mol­ecules are further stacked in pairs, due to intermolecular aromatic π–π interactions and C—H?O hydrogen bonds.     

Disappearance of intramolecular stacking due to one‐atom movement or increment of a `propyl­ene linker' in pyrazolo­[3,4‐d]­pyrimidine‐based ­flexible models

In the crystal structures of 4,6‐di­methyl­thio‐1‐[3‐(4,6‐di­methyl­thio‐2H‐pyra­zolo­[3,4‐d]­py­rimi­din‐2‐yl)­propyl]‐1H‐py­ra­­zolo­[3,4‐d]­py­rimi­dine, C₁₇H₂₀N₈S₄, and 1‐[4‐(4‐meth­oxy‐6‐methyl­thio‐1H‐pyra­zolo­[3,4‐d]py­rimi­din‐1‐yl)­butyl]‐5‐meth­yl‐6‐methyl­thio‐4,5‐di­hydro‐1H‐pyra­zolo­[3,4‐d]py­rimi­din‐4‐one, C₁₈H₂₂N₈O₂S₂, only intermolecular stacking due to aromatic π–π interactions between pyrazolo­[3,4‐d]­pyrimidinerings is present.     

Unusual molecular conformation in dissymmetric propyl­ene‐linker compounds containing pyrazolo­[3,4‐d]­pyrimidine and phthalimide moieties

The crystal structure of 4,6‐bis(methylsulfanyl)‐1‐phthalimidopropyl‐1H‐pyrazolo[3,4‐d]pyrimidine, C₁₈H₁₇N₅O₂S₂, (VI), reveals an unusual folded conformation due to an apparent intramolecular C—H⃛π interaction between the 6‐methyl­­sul­fanyl and phenyl groups. However, the closely related compound 6‐methyl­sulfanyl‐1‐phthalimido­propyl‐4‐(pyrroli­din‐1‐yl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₂₁H₂₂N₆O₂S, (VII), exhibits a fully extended structure, devoid of any intramol­ecular C—H⃛π or π–π interactions. The crystal packing of both mol­ecules involves intermolecular stacking interactions due to aromatic π–π interactions. In addition, (VI) exhibits intermolecular C—H⃛O hydrogen bonding and (VII) exhibits dimerization of the mol­ecules through intermolecular C—H⃛N hydrogen bonding.     

A dimeric layered structure of a 4‐oxo‐4,5‐di­hydro‐1H‐pyrazolo­[3,4‐d]­pyrimidine compound

The title compound, 6‐methyl­sulfanyl‐1‐(3‐phenyl­propyl)‐4,5‐di­hydro‐1H‐pyrazolo­[3,4‐d]­pyrimidin‐4‐one, C₁₅H₁₆N₄OS, crystallizes in space group Pbca, with two mol­ecules of similar structure in the asymmetric unit. The molecular structure shows the absence of intramolecular stacking in the crystalline state, as indicated by earlier ¹H NMR analysis in solution. In addition, the crystal packing reveals the formation of a layered structure, due mainly to intermolecular N—H?O=C hydrogen bonding and arene–arene interactions.     

The regioisomeric 1H(2H)‐pyrazolo[3,4‐d]pyrimidine N1‐ and N2‐(2′‐deoxy‐β‐D‐ribofuranosides)

In the title regioisomeric nucleosides, alternatively called 1‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₁₀H₁₂N₄O₃, (II), and 2‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐2H‐pyrazolo­[3,4‐d]pyrimidine, C₁₀H₁₂N₄O₃, (III), the conformations of the gly­cosyl­ic bonds are anti [?100.4 (2)° for (II) and 15.0 (2)° for (III)]. Both nucleosides adopt an S‐type sugar pucker, which is C2′‐endo‐C3′‐exo (²T₃) for (II) and 3′‐exo (between ₃E and ⁴T₃) for (III).     

8‐Aza‐7‐deaza‐2′‐de­oxy‐2‐(methyl­sulfan­yl)adenosine

In the title compound, 4‐amino‐1‐(2‐de­oxy‐β‐d ‐erythro‐pentofuranos­yl)‐6‐methyl­sulfanyl‐1H‐pyrazolo[3,4‐d]pyrimidine, C₁₁H₁₆N₅O₃S, the conformation of the glycosidic bond is between anti and high anti. The 2′‐deoxy­ribofuranosyl moiety adopts the C3′‐exo–C4′‐endo conformation (₃T⁴, S‐type sugar pucker), and the conformation at the exocyclic C—C bond is +sc (+gauche). The exocyclic 6‐amine group and the 2‐methyl­sulfanyl group lie on different sides of the heterocyclic ring system. The mol­ecules form a three‐dimensional hydrogen‐bonded network that is stabilized by O—H⋯N, N—H⋯O and C—H⋯O hydrogen bonds.     

A stacked pyrazolo[3,4-d]pyrimidine-based flexible molecule: the effect on stacking of an ethyl group in comparison with a methyl group

In the crystal structure of 1,1′-(1,3-propane­diyl)­bis(5-ethyl-6-methyl­thio-4,5-di­hydro-1H-pyrazolo­[3,4-d]­pyrimidin-4-one), C₁₉H₂₄N₈O₂S₂, the pairs of pyrazolo­[3,4-d]­pyrimidine rings of the mol­ecule stack between the heterocyclic rings, due to intramolecular π–π interactions. The substituted ethyl and methyl groups are comparable as far as intramolecular stacking is concerned.     

7‐Vinyl‐8‐aza‐7‐de­aza‐2′‐deoxy­adenosine monohydrate

In the title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐eythro‐pento­furan­osyl)‐3‐vinyl‐1H‐pyrazolo­[3,4‐d]­pyrimidine monohydrate, C₁₂H₁₅N₅O₃·H₂O, the conformation of the gly­cosyl bond is anti. The furan­ose moiety is in an S conformation with an unsymmetrical twist, and the conformation at the exocyclic C—C(OH) bond is +sc (gauche, gauche). The vinyl side chain is bent out of the heterocyclic ring plane by 147.5 (5)°. The three‐dimensional packing is stabilized by O—H·O, O—H·N and N—H·O hydrogen bonds.     

The molecular and supramolecular structures of the isomeric compounds 5,7‐di­methoxy­imidazo­[1,2‐c]­pyrimidine and 7‐methoxy‐1‐methyl­imidazo­[1,2‐a]­pyrimidin‐5(1H)‐one

The supramolecular structures of the isomeric compounds 5,7‐di­methoxy­imidazo­[1,2‐c]­pyrimidine, C₈H₉N₃O₂, (I), and 7‐methoxy‐1‐methyl­imidazo­[1,2‐a]­pyrimidin‐5(1H)‐one, C₈H₉N₃O₂, (II), are determined by weak C—H⃛N and C—H⃛O hydrogen bonds in (I), which generate alternating linked centrosymmetric R(8) and R(10) rings that form a ribbon running parallel to the c axis, and by C—H⃛O bonds in (II), which link the mol­ecules into sheets comprising centro­symmetric R(10) and R(22) rings.     

Folded conformations due to arene interactions in dissymmetric and symmetric butylidene‐linker models based on pyrazolo[3,4‐d]pyrimidine,purine and 7‐deazapurine

The butylidene‐linker models 1‐[2‐(2,6‐dimethylsulfanyl‐9H‐purin‐9‐yl)‐2‐methylidenepropyl]‐4,6‐bis(methylsulfanyl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C₁₈H₂₀N₈S₄, (XI), 7,7′‐(2‐methylidenepropane‐1,3‐diyl)bis[3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one], C₂₀H₂₂N₆O₂S₂, (XIV), and 7‐[2‐(4,6‐dimethylsulfanyl‐1H‐pyrazolo[3,4‐d]pyrimidin‐1‐yl)‐2‐methylidenepropyl]‐3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one, C₁₉H₂₁N₇OS₃, (XV), show folded conformations in solution, as shown by ¹H NMR analysis. This folding carries over to the crystalline state. Intramolecular π–π interactions are observed in all three compounds, but only (XIV) shows additional intramolecular C—H...π interactions in the solid state. As far as can be established, this is the first report incorporating the pyrrolo[2,3‐d]pyrimidine nucleus for such a study. In addition to the π–π interactions, the crystal structures are also stabilized by other weak intermolecular C—H...S/N/O and/or S...N/S interactions.     

Three ginkgolide hydrates from Ginkgo biloba L.: ginkgolide A monohydrate,ginkgolide C sesquihydrate and ginkgolide J dihydrate,all determined at 120 K

A low‐temperature structure of ginkgolide A monohydrate, (1R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐dimethylethyl)‐hexa­hydro‐4,7b‐di­hydroxy‐8‐methyl‐9H‐1,7a‐epoxymethano‐1H,6aH‐cyclo­penta­[c]­furo­[2,3‐b]­furo­[3′,2′:3,4]­cyclopenta­[1,2‐d]­furan‐5,9,12(4H)‐trione monohydrate, C₂₀H₂₄O₉·H₂O, obtained from Mo Kα data, is a factor of three more precise than the previous room‐temperature determination. A refinement of the ginkgolide A monohydrate structure with Cu Kα data has allowed the assignment of the absolute configuration of the series of compounds. Ginkgolide C sesquihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11S,11aR)‐3‐(1,1‐di­methyl­ethyl)‐hexa­hydro‐2,4,7b,11‐tetrahydroxy‐8‐methyl‐9H‐1,7a‐epoxy­methano‐1H,6aH‐cyclopenta­[c]­furo­[2,3‐b]­furo­[3′,2′:3,4]­cyclo­penta­[1,2‐d]­furan‐5,9,12(4H)‐trione sesquihydrate, C₂₀H₂₄O₁₁·1.5H₂O, has two independent diterpene mol­ecules, both of which exhibit intramolecular hydrogen bonding between OH groups. Ginkgolide J dihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐di­methyl­ethyl)‐hexa­hydro‐2,4,7b‐tri­hydroxy‐8‐methyl‐9H‐1,7a‐epoxy­methano‐1H,6aH‐cyclo­penta­[c]­furo­[2,3‐b]furo[3′,2′:3,4]­cyclo­penta­[1,2‐d]­furan‐5,9,12(4H)‐trione dihydrate, C₂₀H₂₄O₁₀·2H₂O, has the same basic skeleton as the other ginkgolides, with its three OH groups having the same configurations as those in ginkgolide C. The conformations of the six five‐membered rings are quite similar across ­ginkgolides A–C and J, except for the A and F rings of ginkgolide A.     

(Z)‐2‐Methylbuten‐1‐yl(aryl)iodonium trifluoromethanesulfonates containing electron‐withdrawing groups on the aryl moiety

The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₂H₁₃F₃I⁺·CF₃O₃S^?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₁H₁₂­Cl₂I⁺·CF₃O₃S^?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C₁₃H₁₂F₆I⁺·­2CF₃­O₃S^?·CH₂Cl₂, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.     

N8‐(2′‐O‐Methyl­ribofuranos­yl)‐8‐aza‐7‐deaza­adenine monohydrate

In the title compound, 4‐amino‐2‐(2‐O‐methyl‐β‐d ‐ribofuranos­yl)‐2H‐pyrazolo[3,4‐d]pyrimidine monohydrate, C₁₁H₁₅N₅O₄·H₂O, the conformation of the N‐glycosylic bond is syn [χ = 20.1 (2)°]. The ribofuran­ose moiety shows a C3′‐endo (³T₂) sugar puckering (N‐type sugar), and the conformation at the exocyclic C4′—C5′ bond is −ap (trans). The nucleobases are stacked head‐to‐head. The three‐dimensional packing of the crystal structure is stabilized by hydrogen bonds between the 2′‐O‐methyl­ribonucleosides and the solvent mol­ecules.     

A highly functionalized ferrocenyl­pyrazolo­[2,3‐a]­pyridine

The crystal structure of [2‐(4‐bromo­phenyl)‐4‐cyano‐5‐ferrocenyl­pyrazolo­[2,3‐a]­pyridin‐7‐yl]­aceto­nitrile, C₂₆H₁₇N₄FeBr or [Fe(C₅H₅)(C₂₁H₁₂BrN₄)], shows that the pyrazolo­pyridine ring system (PP), the bromo­phenyl ring (BP) and the cyclo­penta­diene ring (Cp) are nearly planar. The PP ring system is twisted out of the plane of the BP and Cp rings by about 20°.     

2‐(Pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone and 2‐phenyl­sulfanyl‐3‐(pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone

The structure of 2‐(pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone, C₁₄H_12.95Cl_0.05NO₂, (I), is actually a 0.95:0.05 mixture including 2‐chloro‐3‐(pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone as a minor impurity, but (I) was resolved as a single molecule containing a Cl atom with 5% occupancy at the 3‐position. Compound (I) was prepared from the fully chloro‐substituted analogue in an attempt to produce the disubstituted pyrrolidinyl derivative. 2‐Phenyl­sulfanyl‐3‐(pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone, C₂₀H₁₇NO₂S, (II), was also prepared from 2‐chloro‐3‐(pyrrolidin‐1‐yl)‐1,4‐naphtho­quinone, using a strong exocyclic nucleophile. The structure of (II) differs from previous structures of 2,3‐di­chloro‐1,4‐naphtho­quinone and its derivatives in that the naphtho­quinone ring is non‐planar.     

Thia­mine tetra­phenyl­borate monohydrate: a two‐dimensional hydrogen‐bonded network with (4,4)‐topology

The title compound, 3‐[(4‐amino‐2‐methyl­pyrimidin‐5‐yl)­meth­yl]‐5‐(2‐hydroxy­eth­yl)‐4‐methyl­thia­zolium tetra­phenyl­borate monohydrate, C₁₂H₁₇N₄OS⁺·C₂₄H₂₀B⁻·H₂O, is a salt in which the thiamine cations are linked by hydrogen bonds into a two‐dimensional network having (4,4)‐topology. The stacked sheets form channels, which are occupied by the anions; the cations and anions are linked by C—H⋯π(arene) hydrogen bonds.     

Rotenone α‐oxime

The structure determination of the title compound, rotenone α‐oxime [systematic name: 1,2,12,12a‐tetra­hydro‐8,9‐di­meth­oxy‐2‐(1‐methyl­ethenyl)‐[1]­benzo­py­rano­[3,4‐b]­furo­[2,3‐h][1]benzo­pyran‐6(6H)‐one oxime], C₂₃H₂₃NO₆, confirms that the mol­ecule has an approximately V‐shaped structure. One of the rings has a typical cyclo­hexene‐like monoplanar conformation and the central ring adopts a 1,2‐diplanar conformation.     

7‐Iodo‐8‐aza‐7‐deaza‐2′‐deoxy­adenosine and 7‐bromo‐8‐aza‐7‐deaza‐2′‐deoxyadenosine

The isomorphous structures of the title molecules, 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐3‐iodo‐1H‐pyrazolo‐[3,4‐d]pyrimidine, (I), C₁₀H₁₂IN₅O₃, and 4‐amino‐3‐bromo‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐1H‐pyrazolo[3,4‐d]­pyrimidine, (II), C₁₀H₁₂BrN₅O₃, have been determined. The sugar puckering of both compounds is C1′‐endo (^1′E). The N‐­glycosidic bond torsion angle χ¹ is in the high‐anti range [?73.2 (4)° for (I) and ?74.1 (4)° for (II)] and the crystal structure is stabilized by hydrogen bonds.     

New palladium complexes with phosphino‐ and phosphinitopyridine ligands

Three new palladium complexes containing a difunctional P,N‐chelate, namely tris­(chloro­{[1‐methyl‐1‐(6‐methyl‐2‐pyridyl)ethoxy]diphenylphospine‐κ²N,P}methyl­palladium(II)chloro­form solvate, 3[Pd(CH₃)Cl(C₂₁H₂₂NOP)]·CHCl₃, (III), dichloro­[2‐(2,6‐dimethyl­phen­yl)‐6‐(diphenyl­phosphinometh­yl)­pyridine‐κ²N,P]palladium(II), [PdCl₂(C₂₆H₂₄NP)], (IV), and chloro­[2‐(2,6‐dimethyl­phen­yl)‐6‐(diphenyl­phos­phino­meth­yl)pyridine‐κ²N,P]methyl­palladium(II), [Pd(CH₃)Cl(C₂₆H₂₄NP)], (V), are reported. Geometric data and the conformations of the ligands around the metal centers, as well as slight distortions of the Pd coordination environments from idealized square‐planar geometry, are discussed and compared with the situations in related compounds. Non‐conventional hydrogen‐bond inter­actions (C—H⋯Cl) have been found in all three complexes. Compound (III) is the first six‐membered chloro–meth­yl–phosphinite P,N‐type Pd^II complex to be structurally characterized.