(E)‐1‐(2′‐Deoxy‐β‐d‐ribo­furan­osyl)‐2,4‐di­fluoro‐5‐(2‐iodo­vinyl)­benzene

This analysis of the title compound, C₁₃H₁₃F₂IO₃, establishes the orientation of (E)‐5‐(CH=CH—I) as antiperiplanar (ap) to the C—C bond (5–6 position) of the 2,4‐di­fluoro­phenyl ring system, with the (E)‐5‐(CH=CH—I) H atom located in close proximity (2.17 Å) to the F4 atom of the 2,4‐di­fluoro­phenyl moiety.     

10‐(4‐Fluorophenyl)‐3,3,6,6,9‐pentamethyl‐3,4,6,7,9,10‐hexahydroacridine‐1,8(2H,5H)‐dione and 10‐(4‐fluorophenyl)‐3,3,6,6‐tetramethyl‐9‐­propyl‐3,4,6,7,9,10‐hexahydroacridine‐1,8(2H,5H)‐dione

10‐(4‐Fluoro­phenyl)‐3,3,6,6,9‐penta­methyl‐3,4,6,7,9,10‐hexa­hydro­acridine‐1,8(2H,5H)‐dione, C₂₄H₂₈FNO₂, (I), crystallizes with two crystallographically independent mol­ecules (which differ slightly in conformation), while 10‐(4‐fluoro­phenyl)‐9‐propyl‐3,3,6,6‐tetra­methyl‐3,4,6,7,9,10‐hexa­hydro­acridine‐1,8(2H,5H)‐dione, C₂₆H₃₂FNO₂, (II), crystallizes with one mol­ecule per asymmetric unit. In both structures, the central ring in the acridine moiety is in a sofa conformation, while the outer rings adopt intermediate half‐chair/sofa conformations. The central pyridine ring is orthogonal to the substituted phenyl ring. In both structures, the packing of the crystal is stabilized by C—H?O intermolecular hydrogen bonds.     

Two isomeric 2‐[4‐chloro‐2‐fluoro‐5‐(prop‐2‐ynyloxy)phenyl]hexahydro­isoindole‐1,3‐dione compounds

The molecular structures of 2‐[4‐chloro‐2‐fluoro‐5‐(prop‐2‐ynyloxy)phenyl]‐1,3,4,5,6,7‐hexahydro­isoindole‐1,3‐dione, C₁₇H₁₃ClFNO₃, (I), and the isomeric compound 2‐[4‐chloro‐2‐fluoro‐5‐(prop‐2‐ynyloxy)phenyl]‐cis‐1,3,3a,4,7,7a‐hexahydro­isoindole‐1,3‐dione, (II), are, as anticipated, significantly different in their conformations and in the distances between the farthest two atoms. The six‐membered ring of the 1,3,4,5,6,7‐hexahydro­isoindole‐1,3‐dione moiety in (I) adopts a half‐chair conformation. The dihedral angle between the five‐membered dione ring of (I) and the benzene ring is 50.96 (7)°. The six‐membered ring of the cis‐1,3,3a,4,7,7a‐hexahydro­isoindole‐1,3‐dione moiety in (II) adopts a boat conformation. The dihedral angle in (II) between the five‐membered dione ring and the benzene ring is 61.03 (13)°. In the crystal structures, the molecules are linked by C—H⋯O hydrogen bonds and weak π–π interactions. Compound (I) is a much more potent herbicide than (II). The Cl⋯H distances between the farthest two atoms in (I) and (II) are 11.37 and 9.97 Å, respectively.     

Two N‐substituted 3,5‐diphenyl‐2‐pyrazoline‐1‐thiocarboxamides

The structures of N‐ethyl‐3‐(4‐fluoro­phen­yl)‐5‐(4‐methoxy­phen­yl)‐2‐pyrazoline‐1‐thio­carboxamide, C₁₉H₂₀FN₃OS, (I), and 3‐(4‐fluoro­phen­yl)‐N‐methyl‐5‐(4‐methyl­phen­yl)‐2‐pyrazoline‐1‐thio­carboxamide, C₁₈H₁₈FN₃S, (II), have similar geometric parameters. The meth­oxy/methyl‐substituted phenyl groups are almost perpendicular to the pyrazoline (pyraz) ring [inter­planar angles of 89.29 (8) and 80.39 (10)° for (I) and (II), respectively], which is coplanar with the fluoro­phenyl ring [inter­planar angles of 5.72 (9) and 10.48 (10)°]. The pyrazoline ring approximates an envelope conformation in both structures, with the two‐coordinate N atom involved in an intra­molecular N—H⋯N_pyraz inter­action. In (I), N—H⋯O and C—H⋯S inter­molecular hydrogen bonds are the primary inter­actions, whereas in (II), there are no intermolecular hydrogen bonds.     

5‐Methyl‐2′‐deoxy‐4′‐thio‐α‐uridine (R)‐­S‐oxide

The pyrimidine ring of the title compound, C₁₀H₁₄N₂O₅S, is planar to within 0.024 (1) Å and makes an angle of 75.46 (10)° with the mean plane of the thio­sugar ring. In terms of standard nucleoside nomenclature, this ring has the C3′‐endo conformation. The O5′—C5′—C4′—C3′ torsion angle is 166.5 (3)° and the glycosidic torsion angle S4′—C1′—N1—C2 is ?52.1 (2)° (syn).     

6‐Aza‐2′‐deoxy‐2′‐arabino­fluoro­uridine,a 2′‐deoxy­ribonucleoside with an N‐sugar conformation in the solid state and in solution

In the title compound, 2‐(2‐deoxy‐2‐fluoro‐β‐d ‐arabino­fur­anosyl)‐1,2,4‐triazine‐3,5(2H,4H)‐dione, C₈H₁₀FN₃O₅, the torsion angle of the N‐gly­cosylic bond is anti [χ = −125.37 (13)°]. The furan­ose moiety adopts the N‐type sugar pucker (³T₂), with P = 359.2° and τ_m = 31.4°. The conformation around the C4′—C5′ bond is antiperiplanar (trans), with a torsion angle γ of 177.00 (11)°. A network is formed via hydrogen bonds from the nucleobases to the sugar residues, as well as through hydrogen bonds between the sugar moieties.     

3‐(3‐Oxo‐1,3‐dihydroisobenzofuran‐1‐ylidene)pentane‐2,4‐dione

In the title compound, C₁₃H₁₀O₄, prepared by the condensation reaction between phthalic anhydride and pentane‐2,4‐dione, one of the acetyl groups in the pentane‐2,4‐dione fragment is almost coplanar with the isobenzofuran ring system, while the other group is twisted out of this plane by almost 80°. The corresponding C—C and C—O distances in the two acetyl units are consistent with dipolar delocalization into the coplanar unit only. There is no supramolecular aggregation of the molecules, but a number of rather short intermolecular contacts of C—H...O, O...O and O...C types occur.     

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil,a cyclouridine nucleoside with a C4′‐endo furanosyl conformation

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil, C₁₃H₁₄N₂O₇, was obtained by refluxing 2′,3′‐O‐(methoxymethylene)uridine in acetic anhydride. The structure exhibits a nearly perfect C4′‐endo (⁴E) conformation. The best four‐atom plane of the five‐membered furanose ring is O—C—C—C, involving the C atoms of the fused five‐membered oxazolidine ring, and the torsion angle is only −0.4 (2)°. The oxazolidine ring is essentially coplanar with the six‐membered uracil ring [r.m.s. deviation = 0.012 (5) Å and dihedral angle = −3.2 (3)°]. The conformation at the exocyclic C—C bond is gauche–trans which is stabilized by various C—H...π and C—O...π interactions.     

1,1′‐Di­acetyl‐3‐hydroxy‐2,2′,3,3′‐tetra­hydro‐3,3′‐bi(1H‐indole)‐2,2′‐dione

In the title compound, C₂₀H₁₆N₂O₅, both of the 1‐acetyl­isatin (1‐acetyl‐1H‐indole‐2,3‐dione) moieties are planar and form a dihedral angle of 74.1 (1)°. Weak intermolecular hydrogen bonds and C—H?π interactions stabilize the packing in the crystal.     

N‐Fluoropyridinium trifluoromethanesulfonate and 1‐fluoro‐2,4,6‐trimethoxy‐1,3,5‐triazinium hexafluoroantimonate: the first experimental determination of the F—N+ bond length involving sp2 nitrogen

The structures of N‐fluoro­pyridinium tri­fluoro­methane­sulfon­ate, C₅H₅FN⁺·CF₃O₃S⁻, (I), and 1‐fluoro‐2,4,6‐tri­methoxy‐1,3,5‐triazinium hexa­fluoro­antimonate, (C₆H₉FN₃O₃)[SbF₆], (II), are presented. The N—F bond lengths in (I), a well known electrophilic fluorinating agent, and its novel analogue, (II), are 1.357 (4) and 1.354 (4) Å, respectively.     

5‐Ethyl‐2′‐deoxy‐4′‐thiouridine (R)‐S‐oxide monohydrate

The pyrimidine ring of the title compound, C₁₁H₁₆N₂O₅S·H₂O, is planar to within 0.026 (1) Å and makes an angle of 77.73 (8)° with the mean plane of the thiosugar ring. In terms of standard nucleoside nomenclature, this ring has a C1′‐exo,C2′‐endo conformation. The O5′—C5′—C4′—C3′ torsion angle is ?167.4 (2)° and the glycosidic S4′—C1′—N1—C2 torsion angle is ?101.8 (2)° (anti).     

3‐(Triphenyl­phospho­ranyl­idene)pentane‐2,4‐dione and dieth­yl 2‐(triphenyl­phospho­ranyl­idene)malonate

The title ylides, 3‐(triphenyl­phospho­ranyl­idene)pentane‐2,4‐dione, C₂₃H₂₁O₂P, (I), and diethyl 2‐(triphenyl­phospho­ranyl­idene)malonate, C₂₅H₂₅O₄P, (II), differ in the conformations adopted by their extended ylide moieties. In (I), one carbonyl O atom is syn and the other is anti with respect to the P atom, the ylide group is nearly planar, with a maximum P—C—(C=O) angle of 18.2 (2)°, and the P—C, C—C and C=O bond lengths are consistent with electronic delocalization involving the O atoms. In (II), both carbonyl O atoms are anti and the ester groups are twisted out of the plane of the near trigonal ylide C atom, reducing delocalization, the largest P—C—(C=O) angle being 30.2 (2)°.     

Benzyl 5‐{2‐[2‐(diethoxy­phosphinoyl)­acetyl]‐3‐oxo‐7‐thia‐2,4‐di­aza­bi­cyclo­[3.3.0]­oct‐6‐yl}pentanoate,a novel biotin derivative

The title compound, C₂₃H₃₃N₂O₇PS, has its phospho­no­acetate carbonyl group rotated slightly out of the plane of the ureido ring, with a C—N—C—O torsion angle of ?6.9 (4)°. The sulfur‐containing ring has an envelope conformation, while the ureido ring is nearly planar.     

The 7‐bromo derivative of 2‐amino‐2′‐deoxytubercidin fluorinated at the sugar moiety

The title compound, 2,4‐diamino‐5‐bromo‐7‐(2‐deoxy‐2‐fluoro‐β‐d ‐arabinofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine, C₁₁H₁₃BrFN₅O₃, shows two conformations of the exocyclic C4′—C5′ bond, with the torsion angle γ (O5′—C5′—C4′—C3′) being 170.1 (3)° for conformer 1 (occupancy 0.69) and 60.7 (7)° for conformer 2 (occupancy 0.31). The N‐glycosylic bond exhibits an anti conformation, with χ = −114.8 (4)°. The sugar pucker is N‐type (C3′‐endo; ³T₄), with P = 23.3 (4)° and τ_m = 36.5 (2)°. The compound forms a three‐dimensional network that is stabilized by several intermolecular hydrogen bonds (N—H...O, O—H...N and N—H...Br).     

2′,3′‐Dide­hydro‐3′‐deoxy­thymidine N‐methyl‐2‐pyrrolidone solvate (D4T·NMPO)

The title compound, 1‐(2′,3′‐di­deoxy‐β‐d ‐glycero‐pent‐2‐eno­furan­osyl)­thymine 1‐methyl‐2‐pyrrolidone solvate, C₁₀H₁₂N₂O₄·­C₅H₉NO, is an NMPO solvate of the anti‐AIDS agent D4T. In its crystal structure, both the pyrimidine and the furan­ose rings are planar and approximately perpendicular [82.1 (4)°]. The value of the torsion angle defining the orientation of the thymine with respect to the joined furane, χ = ?100.8 (4)°, and that of the torsion angle giving the orientation of the hydroxyl group linked to the furane ring, γ = 52.9 (5)°, show that the gly­cosyl­ic link adopts the so‐called high‐anti conformation and the 5′‐hydroxyl group is in the +sc position. The NMPO solvate is linked to the nucleoside through a fairly strong hydrogen bond.     

1‐(1H‐Indol‐3‐ylcarbonyl)‐N‐(4‐methoxy­benzyl)formamide

In the title compound, C₁₈H₁₆N₂O₃, the indole ring is planar and the two adjacent carbonyl groups are mutually trans oriented with a torsion angle of 144.8 (3)°. The single C—C bond linking the two carbonyl functionalities is 1.539 (4) Å. Mol­ecules are linked into a two‐dimensional network by inter­molecular N—H⋯O hydrogen bonds.     

4‐(4‐Fluoro‐3‐phenoxy­phen­yl)‐6‐(4‐fluoro­phen­yl)‐2‐oxo‐1,2‐dihydro­pyridine‐3‐carbonitrile and the 6‐(4‐methyl­phen­yl)‐ analogue

The crystal structures of the title compounds, viz. C₂₄H₁₄F₂N₂O₂, (I), and C₂₅H₁₇FN₂O₂, (II), respectively, have been determined in order to unravel the role of an ordered F atom in generating stable supra­molecular assemblies. On changing the substitution from fluorine to a methyl group, C—H⋯F inter­actions are replaced by C—H⋯π inter­actions, revealing the importance of such weak inter­actions when present alongside N—H⋯O and C—H⋯O hydrogen bonds. The dihedral angle between the planes of the 4‐fluoro­phenyl ring and the pyridine ring is 26.8 (1)° in (I), while that between the planes of the 4‐methyl­phenyl and pyridine rings is 29.5 (1)° in (II).     

6‐(3,4‐Di­fluoro­benzoyl)‐3‐[2‐(4‐pyridyl)­ethyl]‐1,3‐benzo­thia­zol‐2(3H)‐one

A new type of benzo­thia­zolinone derivative with potential pharmacological activity, viz. 6‐(3,4‐di­fluoro­benzoyl)‐3‐[2‐(4‐pyridyl)­ethyl]‐1,3‐benzo­thia­zol‐2(3H)‐one, C₂₁H₁₄F₂N₂O₂S, has been prepared and studied by NMR, IR and single‐crystal X‐ray diffraction techniques. The mol­ecule is not planar, the pyridine and di­fluoro­benzene moieties being located above and below the benzo­thia­zole ring system. The carbonyl O atoms are involved in an intramolecular hydrogen‐bond‐type interaction.     

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.     

Ethyl 5‐methyl‐4‐(2,5,5‐tri­methyl‐1,3‐dioxan‐2‐yl)­isoxazole‐3‐carboxyl­ate

The title compound, C₁₄H₂₁NO₅, possesses an isoxazolyl group in the axial position of the 1,3‐dioxanyl ring. The two rings are rotated about the bond joining them such that the two C(methyl)—C(dioxanyl)—C—C torsion angles are 92.1 (2) and ?84.1 (2)°. In this conformation, neither the methyl nor ethoxy­carbonyl substituents on the isoxazole are presented towards the dioxanyl chair.