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.     

Intermolecular stacking in pyrazolo[3,4‐d]pyrimidine‐based pentamethylene‐linked flexible ­molecules

The crystal structures of 1‐{5‐[4,6‐bis­(methyl­sulfanyl)‐2H‐py­razolo­[3,4‐d]­pyrimidin‐2‐yl]­pentyl}‐6‐methyl­sulfanyl‐4‐(pyr­rolidin‐1‐yl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₂₂H₂₉N₉S₃, and 6‐methyl­sulfanyl‐1‐{5‐[6‐methyl­sulfanyl‐4‐(pyrrolidin‐1‐yl)‐2H‐pyrazolo­[3,4‐d]­pyrimidin‐2‐yl]­pentyl}‐4‐(pyrrolidin‐1‐yl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₂₅H₃₄N₁₀S₂, which differ in having either a pyrrolidine substituent or a methylsulfanyl group, show intermolecular stacking due to aromatic π–π interactions between the pyrazolo­[3,4‐d]­pyrimidine rings.     

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.     

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.     

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.     

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.     

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.     

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).     

An anthracene dimer with a fused 1,3‐dithiole ring at 193 K

The first butterfly‐shaped anthracene dimer including S atoms,8,9‐di­hydro‐3a,8[1′,2′]:9,13b[1′′,2′′]­di­benzeno­dibenzo­[3,4:7,8]cyclo­octa­[1,2‐d]‐1,3‐di­thiole, C₂₉H₂₀S₂, contains an exceptionally long Csp³—Csp³ bond of 1.672 (2) Å in the fused 1,3‐di­thiole ring. The length of the other bond bridging the anthracene moieties is 1.604 (3) Å.     

Three 5H‐indeno­[1,2‐c]­pyridazin‐5‐one derivatives,potent type‐B mono­amine oxidase inhibitors

The structures of three compounds, namely 7‐methoxy‐2‐[3‐(tri­fluoro­methyl)­phenyl]‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₉H₁₁F₃N₂O₂, (Id), 6‐methoxy‐2‐[3‐(tri­fluoro­methyl)­phenyl]‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₉H₁₁F₃N₂O₂, (IId), and 2‐methyl‐6‐(4,4,4‐tri­fluoro­butoxy)‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₆H₁₃F₃N₂O₂, (IIf), which are potent reversible type‐B mono­amine oxidase (MAO‐B) inhibitors, are presented and discussed. Compounds (Id) and (IId) crystallize in a nearly planar conformation. The crystal structures are stabilized by weak C—H⋯O hydrogen bonds. The packing is dominated by π–π stacking interactions between the heterocyclic central moieties of centrosymmetrically related mol­ecules. In compound (IIf), the tri­fluoro­ethyl termination is almost perpendicular to the plane of the ring.     

A zirconium zwitterion containing a caged amine H atom

The crystallographically centrosymmetric zwitterion bis­[tris(3,5‐di­methyl‐2‐oxidobenzyl‐κO)­ammonium]­zirconium(IV) crystallizes as the chloro­form disolvate, [Zr(C₂₇H₃₁NO₃)₂]·2CHCl₃, with the two mol­ecules of chloro­form closely associated with two of the aromatic rings. The Zr atom has a distorted octahedral geometry with three phenoxy O atoms from each of the two ligands coordinated to it. Charge balance is maintained by protonation of each N atom, which then forms intramolecular hydrogen‐bonding interactions to all three adjacent O atoms.     

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.     

Cyclofunctionalization of 6-alkenylsulfanylpyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]-pyrimidin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones with arenesulfenyl chlorides

Reactions of 6-allylsulfanylpyrazolo[3,4-d]pyrimidin-4(5H)-one with arenesulfenyl chlorides in chloroform gave products of addition of the latter at the exocyclic double bond, while analogous reactions in acetic acid in the presence of LiClO₄ were accompanied by intramolecular electrophilic cyclization involving the N⁷ atom. 6-Cinnamylsulfanylpyrazolo[3,4-d]pyrimidin-4(5H)-one reacted with arenesulfenyl chlorides in acetic acid in the absence of electrolyte to produce fused pyrazolo[4′,3′: 5,6]pyrimido[2,1-b][1,3]thiazine derivatives. Introduction of a bulky phenyl group into position 1 of the pyrazolo[3,4-d]pyrimidine system reduces the yield of the corresponding intramolecular cyclization product at N⁷ as a result of concurrent formation of acyclic addition product. DOI     

A novel binucleating macrocyclic ligand with two alcohol pendants

A novel binucleating 24‐membered macrocyclic ligand, 6,20‐bis(2‐hydroxy­ethyl)‐3,6,9,17,20,23‐hex­aza­tri­cyclo­[23.3.1.1^11,15]triaconta‐1(29),11(30),12,14,25,27‐hexaene (L), was synthesized and crystallized as the tetra­hydro­bromide salt, i.e. 6,20‐bis(2‐hydroxy­ethyl)‐6,20‐di­aza‐3,9,17,23‐hexa­azoniatri­cyclo­[23.3.1.1^11,15]­triaconta‐1(29),11(30),­12,14,25,27‐hexaene tetrabromide tetrahydrate, C₂₈H₅₀N₆O₂⁴⁺·­4Br^?·4H₂O. A crystallographic inversion center is located in the macrocyclic cavity and the two hydroxy­ethyl pendants are on opposite sides of the macrocyclic plane. The benzene rings of the macrocycle are parallel to each other and a π–π‐stacking interaction exists between the benzene rings of adjacent macrocycles, which are separated by 3.791 (9) Å. An infinite intermolecular hydrogen‐bond network stabilizes the crystal.     

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.     

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.     

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.     

(–)-Argemonine hemihydrate

(−)-Argemonine hemihydrate [systematic name: (6S,12S)-2,3,8,9-tetra­methoxy-13-methyl-13-aza­dibenzo­[b,f]­bi­cyclo[3.3.1]­nona-2,6-diene hemi­hy­drate], C₂₁H₂₅NO₄·0.5H₂O, is a tertiary pavinane alkaloid. Both partially saturated nitro­gen heterocycles adopt twisted half-chair conformations. The angle between the two aromatic rings is 86.90 (5)°.