Synthesis of spiro[indoline‐3,3′‐pyrrolizines] by 1,3‐dipolar reactions between isatins,l‐proline and electron‐deficient alkenes

Two spiro[indoline‐3,3′‐pyrrolizine] derivatives have been synthesized in good yield with high regio‐ and stereospecificity using one‐pot reactions between readily available starting materials, namely l ‐proline, substituted 1H‐indole‐2,3‐diones and electron‐deficient alkenes. The products have been fully characterized by elemental analysis, IR and NMR spectroscopy, mass spectrometry and crystal structure analysis. In (1′RS ,2′RS ,3SR ,7a′SR )‐2′‐benzoyl‐1‐hexyl‐2‐oxo‐1′,2′,5′,6′,7′,7a′‐hexahydrospiro[indoline‐3,3′‐pyrrolizine]‐1′‐carboxylic acid, C₂₈H₃₂N₂O₄, (I), the unsubstituted pyrrole ring and the reduced spiro‐fused pyrrole ring adopt half‐chair and envelope conformations, respectively, while in (1′RS ,2′RS ,3SR ,7a′SR )‐1′,2′‐bis(4‐chlorobenzoyl)‐5,7‐dichloro‐2‐oxo‐1′,2′,5′,6′,7′,7a′‐hexahydrospiro[indoline‐3,3′‐pyrrolizine], which crystallizes as a partial dichloromethane solvate, C₂₈H₂₀Cl₄N₂O₃·0.981CH₂Cl₂, (II), where the solvent component is disordered over three sets of atomic sites, these two rings adopt envelope and half‐chair conformations, respectively. Molecules of (I) are linked by an O—H…·O hydrogen bond to form cyclic R ₆⁶(48) hexamers of (S ₆) symmetry, which are further linked by two C—H…O hydrogen bonds to form a three‐dimensional framework structure. In compound (II), inversion‐related pairs of N—H…O hydrogen bonds link the spiro[indoline‐3,3′‐pyrrolizine] molecules into simple R ₂²(8) dimers.     

Di‐2‐pyridyl ketone 4‐methyl‐4‐phenyl­thio­semicarbazone

The mol­ecule of the title compound, C₁₉H₁₇N₅S, adopts a Z configuration about the azomethine bond and exists as the thione tautomer. The overall structure of the mol­ecule is distributed in four different planes. An intramolecular hydrogen bond involving the pyridyl N atom and the H atom attached to the hydrazine N atom leads to the formation of a six‐membered ring.     

Heterocyclic tautomerism: reassignment of two crystal structures of 2‐amino‐1,3‐thiazolidin‐4‐one derivatives

The structures of 5‐(2‐hydroxyethyl)‐2‐[(pyridin‐2‐yl)amino]‐1,3‐thiazolidin‐4‐one, C₁₀H₁₁N₃O₂S, (I), and ethyl 4‐[(4‐oxo‐1,3‐thiazolidin‐2‐yl)amino]benzoate, C₁₂H₁₂N₂O₃S, (II), which are identical to the entries with refcodes GACXOZ [Váňa et al. (2009). J. Heterocycl. Chem. 46 , 635–639] and HEGLUC [Behbehani & Ibrahim (2012). Molecules, 17 , 6362–6385], respectively, in the Cambridge Structural Database [Allen (2002). Acta Cryst. B 58 , 380–388], have been redetermined at 130 K. This structural study shows that both investigated compounds exist in their crystal structures as the tautomer with the carbonyl–imine group in the five‐membered heterocyclic ring and an exocyclic amine N atom, rather than the previously reported tautomer with a secondary amide group and an exocyclic imine N atom. The physicochemical and spectroscopic data of the two investigated compounds are the same as those of GACXOZ and HEGLUC, respectively. In the thiazolidin‐4‐one system of (I), the S and chiral C atoms, along with the hydroxyethyl group, are disordered. The thiazolidin‐4‐one fragment takes up two alternative locations in the crystal structure, which allows the molecule to adopt R and S configurations. The occupancy factors of the disordered atoms are 0.883 (2) (for the R configuration) and 0.117 (2) (for the S configuration). In (I), the main factor that determines the crystal packing is a system of hydrogen bonds, involving both strong N—H...N and O—H...O and weak C—H...O hydrogen bonds, linking the molecules into a three‐dimensional hydrogen‐bond network. On the other hand, in (II), the molecules are linked via N—H...O hydrogen bonds into chains.     

Flip‐type disorder in 3‐substituted 2,2′:5′,2′′‐terthiophenes

In the crystal structures of four thiophene derivatives, (E)‐3′‐[2‐(anthracen‐9‐yl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₂₈H₁₈S₃, (E)‐3′‐[2‐(1‐pyrenyl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₃₀H₁₈S₃, (E)‐3′‐[2‐(3,4‐dimethoxyphenyl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₂₂H₁₈O₂S₃, and (E,E)‐1,4‐bis[2‐(2,2′:5′,2′′‐terthiophen‐3′‐yl)ethenyl]‐2,5‐dimethoxybenzene, C₃₆H₂₆O₂S₆, at least one of the terminal thiophene rings is disordered and the disorder is of the flip type. The terthiophene fragments are far from being coplanar, contrary to terthiophene itself. The central C—C=C—C fragments are almost planar but the bond lengths suggest slight delocalization within this fragment. The crystal packing is determined by van der Waals interactions and some weak, relatively short, C—H...S and C—H...π directional contacts.     

[(bdp)FeBr]: Structural Determination of a Polymorphic Iron Chelate with an Open‐Chain Tetrapyrrolic Ligand

Bromido‐(3,3′,4,4′,8,8′,9,9′‐octaethyl‐2,2′‐bidipyrrinato)iron(III) crystallizes in two different polymorphs, space groups and C2/c, with Z = 2 and 8, respectively, and slightly different densities. The Fe‐N and Fe‐Br bond lengths vary significantly with the polymorph indicating the presence of intermediate spin (S = 3/2) species admixed with different amounts of high spin (S = 5/2) iron(III) compounds in the triclinic resp. monoclinic form.     

Four N7‐alkoxybenzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones: hydrogen‐bonded supramolecular structures in zero,one, two or three dimensions

3‐tert‐Butyl‐7‐(4‐methoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₇N₃O₃, (I), 3‐tert‐butyl‐7‐(2,3‐dimethoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₂H₃₉N₃O₄, (II), 3‐tert‐butyl‐4′,4′‐dimethyl‐7‐(3,4‐methylenedioxybenzyl)‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₅N₃O₄, (III), and 3‐tert‐butyl‐4′,4′‐dimethyl‐1‐phenyl‐7‐(3,4,5‐trimethoxybenzyl)‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol 0.67‐solvate, C₃₃H₄₁N₃O₅·0.67C₂H₆O, (IV), all contain reduced pyridine rings having half‐chair conformations. The molecules of (I) and (II) are linked into centrosymmetric dimers and simple chains, respectively, by C—H...O hydrogen bonds, augmented only in (I) by a C—H...π hydrogen bond. The molecules of (III) are linked by a combination of C—H...O and C—H...π hydrogen bonds into a chain of edge‐fused centrosymmetric rings, further linked by weak hydrogen bonds into supramolecular arrays in two or three dimensions. The heterocyclic molecules in (IV) are linked by two independent C—H...O hydrogen bonds into sheets, from which the partial‐occupancy ethanol molecules are pendent. The significance of this study lies in its finding of a very wide range of supramolecular aggregation modes dependent on rather modest changes in the peripheral substituents remote from the main hydrogen‐bond acceptor sites.     

Two stereoisomeric pentacyclic oxin­dole alkaloids from Uncaria tomentosa: uncarine C and uncarine E

The chloro­form solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octa­hydro‐1′‐methyl‐2‐oxospiro­[3H‐indole‐3,6′(4′aH)‐[1H]­pyrano­[3,4‐f]indolizine]‐4′‐carboxyl­ic acid methyl ester, C₂₁H₂₄N₂O₄·CHCl₃, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C₂₁H₂₄N₂O₄, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the ox­indole, with N?O distances in the range 2.759 (4)–2.894 (5) Å.     

Synthesis and characterization of (6‐{[2‐(pyridin‐2‐yl)hydrazinylidene]methyl}pyridin‐2‐yl)methanol: a supramolecular and topological study

Hydrazones exhibit a versatile chemistry and are of interest for their potential use as functional molecular systems capable of undergoing reversible changes of configuration, i.e. E/Z isomerization. The title compound, C₁₂H₁₂N₄O, has an E configuration with respect to the hydrazone C=N bond. The crystal packing is formed by N—H...N and O—H...N hydrogen bonds that give a two‐dimensional layer structure and C—H...C interactions associated with layer stacking to produce the three‐dimensional supramolecular structure. These intermolecular interactions were analyzed and quantified by the Hirshfeld surface method and the two‐dimensional supramolecular arrangement was topologically simplified as a hcb network.     

Different nucleobase orientations in two cyclic 2′,3′‐phosphates of purine ribonucleosides: Et3NH(2′,3′‐cAMP) and Et3NH(2′,3′‐cGMP)·H2O

The crystal structures of triethyl­ammonium adenosine cyclic 2′,3′‐phosphate {systematic name: triethyl­ammonium 4‐(6‐amino­purin‐9‐yl)‐6‐hydroxy­methyl‐2‐oxido‐2‐oxoperhydro­furano[3,4‐c][1,3,2]dioxaphosphole}, Et₃NH(2′,3′‐cAMP) or C₆H₁₆N⁺·C₁₀H₁₁N₅O₆P⁻, (I), and guanosine cyclic 2′,3′‐phosphate monohydrate {systematic name: triethyl­ammonium 6‐hydroxy­methyl‐2‐oxido‐2‐oxo‐4‐(6‐oxo‐1,6‐dihydro­purin‐9‐yl)perhydro­furano[3,4‐c][1,3,2]dioxaphosphole monohydrate}, [Et₃NH(2′,3′‐cGMP)]·H₂O or C₆H₁₆N⁺·C₁₀H₁₁N₅O₇P⁻·H₂O, (II), reveal different nucleobase orientations, viz. anti in (I) and syn in (II). These are stabilized by different inter‐ and intra­molecular hydrogen bonds. The structures also exhibit different ribose ring puckering [₄E in (I) and ³T₂ in (II)] and slightly different 1,3,2‐dioxaphospho­lane ring conformations, viz. envelope in (I) and puckered in (II). Infinite ribbons of 2′,3′‐cAMP⁻ and helical chains of 2′,3′‐cGMP⁻ ions, both formed by O—H⋯O, N—H⋯X and C—H⋯X (X = O or N) hydrogen‐bond contacts, characterize (I) and (II), respectively.     

Novel hydrazone derivatives of 7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐carbaldehyde

The structures of new oxaindane spiropyrans derived from 7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐carbaldehyde (SP1), namely N‐benzyl‐2‐[(7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐yl)methylidene]hydrazinecarbothioamide, C₂₇H₂₅N₃O₃S, (I), at 120 (2) K, and N′‐[(7‐hydroxy‐3′,3′‐dimethyl‐3′H‐spiro[chromene‐2,1′‐isobenzofuran]‐8‐yl)methylidene]‐4‐methylbenzohydrazide acetone monosolvate, C₂₇H₂₄N₂O₄·C₃H₆O, (II), at 100 (2) K, are reported. The photochromically active C_spiro—O bond length in (I) is close to that in the parent compound (SP1), and in (II) it is shorter. In (I), centrosymmetric pairs of molecules are bound by two equivalent N—H...S hydrogen bonds, forming an eight‐membered ring with two donors and two acceptors.     

Acid?Base Properties of Adenosine 5′‐Monophosphate,Guanosine 5′‐Monophosphate,and Inosine 5′‐Monophosphate in Aqueous Solutions of Methanol

The protonation constants of adenosine 5′‐monophosphate, guanosine 5′‐monophosphate, and inosine 5′‐monophosphate were determined in binary mixtures of H₂O containing 0, 10, 15, 20, 25, 30, 35, 40, 45, and 50% MeOH, using a combination of potentiometric and spectrophotometric methods at a constant temperature (25°) and constant ionic strength (0.1 mol?dm^?3 NaClO₄). The protonation constants were analyzed using the normalized polarity parameter (E ), and Kamlet, Abboud, and Taft (KAT) parameters. A linear correlation of log K vs. the normalized polarity parameter was obtained. Dual‐parameter correlation of log K vs. π* (dipolarity/polarizability) and α (H‐bond‐donor acidity), as well as π* and β (H‐bond‐acceptor basicity) also gives good results in various aqueous organic solvent mixtures. Finally, the results are discussed in terms of the effect of solvent on the protonation equilibria.     

A Synthetic,Structural, Spectroscopic and DFT study of ReI,CuI, RuII and IrIII Complexes Containing Functionalised Dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz)

The ligands 11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine and 2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole have been coordinated to Re^I, Cu^I, Ru^II and Ir^III metal centres. Single‐crystal X‐ray analyses were performed on fac‐chlorotricarbonyl(11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine)rhenium (C₂₂H₉ClN₅O₃Re, a=6.509(5), b=12.403(5), c=13.907(5) Å, α=96.88(5), β=92.41(5), γ=92.13(5)°, triclinic, P , Z=2) and bis‐2,2′‐bipyridyl(2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole)ruthenium triflate ? 2 CH₃CN (C₅₂H₃₆F₆N₁₂O₈RuS₂, a=10.601(5), b=12.420(5), c=20.066(5) Å, α=92.846(5), β=96.493(5), γ=103.720(5)°, triclinic, P , Z=2). The ground‐ and excited‐state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited‐state lifetime studies. Spectroscopic, time‐resolved and DFT studies reveal that the ligand‐centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower‐lying metal‐to‐ligand charge‐transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the ³LC state is populated.     

(E/Z)‐Isomerization of 3′‐Epilutein

3′‐Epilutein (=(all‐E,3R,3′S,6′R)‐4′,5′‐didehydro‐5′,6′‐dihydro‐β,β‐carotene‐3,3′‐diol; 1 ), isolated from the flowers of Caltha palustris, was submitted to both thermal isomerization and I₂‐catalyzed photoisomerization. The structures of the main products (9Z)‐ 1 , (9′Z)‐ 1 , (13Z)‐ 1 , (13′Z)‐ 1 , (15Z)‐ 1 , and (9Z,9′Z)‐ 1 were determined based on UV/VIS, CD, ¹H‐NMR, and MS data.     

Regio‐ and stereospecific assembly of dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidines] from simple precursors using a one‐pot procedure: synthesis,spectroscopic and structural characterization,and a proposed mechanism of formation

The synthesis and characterization of three new dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine] compounds are reported, together with the crystal structures of two of them. (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐Chlorophenyl)‐1‐hexyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₈H₃₀ClN₃O₂S₂, (I), (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐1‐benzyl‐5‐methyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₃₀H₂₆ClN₃O₂S₂, (II), and (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐5‐fluoro‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₂H₁₇ClFN₃O₂S₂, (III), were each isolated as a single regioisomer using a one‐pot reaction involving l ‐proline, a substituted isatin and (Z)‐5‐(4‐chlorobenzylidene)‐2‐sulfanylidenethiazolidin‐4‐one [5‐(4‐chlorobenzylidene)rhodanine]. The compositions of (I)–(III) were established by elemental analysis, complemented by high‐resolution mass spectrometry in the case of (I); their constitutions, including the definition of the regiochemistry, were established using NMR spectroscopy, and the relative configurations at the four stereogenic centres were established using single‐crystal X‐ray structure analysis. A possible reaction mechanism for the formation of (I)–(III) is proposed, based on the detailed stereochemistry. The molecules of (I) are linked into simple chains by a single N—H…N hydrogen bond, those of (II) are linked into a chain of rings by a combination of N—H…O and C—H…S=C hydrogen bonds, and those of (III) are linked into sheets by a combination of N—H…N and N—H…S=C hydrogen bonds.     

Intermolecular C—H...O and C—H...X interactions in substituted spiroacenaphthylene structures

In the three spiroacenaphthylene structures 5′′‐[(E)‐2,3‐dichlorobenzylidene]‐7′‐(2,3‐dichlorophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₆Cl₄N₂O₂S, (I), 5′′‐[(E)‐4‐fluorobenzylidene]‐7′‐(4‐fluorophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₈F₂N₂O₂S, (II), and 5′′‐[(E)‐4‐bromobenzylidene]‐7′‐(4‐bromophenyl)‐1′′‐methyldispiro[acenaphthylene‐1,5′‐pyrrolo[1,2‐c][1,3]thiazole‐6′,3′′‐piperidine]‐2,4′′‐dione, C₃₅H₂₈Br₂N₂O₂S, (III), the substituted aryl groups are 2,3‐dichloro‐, 4‐fluoro‐ and 4‐bromophenyl, respectively. The six‐membered piperidine ring in all three structures adopts a half‐chair conformation, the thiazolidine ring adopts a slightly twisted envelope and the pyrrolidine ring an envelope conformation; in each case, the C atom linking the rings is the flap atom. In all three structures, weak intramolecular C—H...O interactions are present. The crystal packing is stabilized through a number of intermolecular C—H...O and C—H...X interactions, where X = Cl in (I) and F or S in (II), and C—H...O interactions are observed predominantly in (III). In all three structures, molecules are linked through centrosymmetric ring motifs, further tailored through a relay of C—H...X [Cl in (I), Br in (II) and O in (III)] interactions.     

Quinoline‐2(1H)‐thione,a structure with Z′ = 8

The title compound, C₉H₇NS, crystallizes as the thione tautomer with Z′ = 8 (four independent dimers with local inversion symmetry via two N—H⋯S=C hydrogen‐bond systems). The dimers are arranged in chains parallel to [10], each chain being crystallographically independent. These chains are associated into layers via stacking of ring systems. The Z′ value can be rationalized in terms of a factor 2 for dimer formation without crystallographic symmetry and an additional factor 4 for differing stacking environments.     

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.     

Biphenyl‐ and phenylnaphthalenyl‐substituted 1H‐imidazole‐4,5‐dicarbonitrile catalysts for the coupling reaction of nucleoside methyl phosphonamidites

Crystal structures are reported for three substituted 1H‐imidazole‐4,5‐dicarbonitrile compounds used as catalysts for the coupling reaction of nucleoside methyl phosphonamidites, namely 2‐(3′,5′‐dimethylbiphenyl‐2‐yl)‐1H‐imidazole‐4,5‐dicarbonitrile, C₁₉H₁₄N₄, (I), 2‐(2′,4′,6′‐trimethylbiphenyl‐2‐yl)‐1H‐imidazole‐4,5‐dicarbonitrile, C₂₀H₁₆N₄, (II), and 2‐[8‐(3,5‐dimethylphenyl)naphthalen‐1‐yl]‐1H‐imidazole‐4,5‐dicarbonitrile, C₂₃H₁₆N₄, (III). The asymmetric unit of (I) contains two independent molecules with similar conformations. There is steric repulsion between the imidazole group and the terminal phenyl group in all three compounds, resulting in the nonplanarity of the molecules. The naphthalene group of (III) shows significant deviation from planarity. The C—N bond lengths in the imidazole rings range from 1.325 (2) to 1.377 (2) Å. The molecules are connected into zigzag chains by intermolecular N—H...N_imidazole [for (I)] or N—H...·N_cyano [for (II) and (III)] hydrogen bonds.     

2‐Hydroxy­acetophenone 4‐phenyl­thio­semicarbazone

The title compound, C₁₅H₁₅N₃OS, exists in the thione form and adopts an E configuration about the hydrazine bond, which is in the Z form with respect to the thiocarbonyl bond. An O—H⋯N intra­molecular hydrogen bond promotes planarity in part of the mol­ecule.     

Struktur der Valenciaxanthine und Valenciachrome

Structure of the Valenciaxanthins and Valenciachromes Valenciaxanthin, a carotenoid first isolated from Californian Valencia orange juice in 1952/1954 by American scientists, was re-isolated from fresh Spanish ‘Navelinas’ and shown, by spectroscopical and chiroptical examination, to have the unexpected (9Z)-10′-apo-11′,12′-dihydroviolaxantin-10′-ol structure 6 . A further, very minor component represents the (all-E)-structure 7 . Therefore, the Valenciachromes are the furanoid rearrangement products of 6 and 7 and, thus, stereoisomers of the 10′-apo-11′,12′-dihydroauroxanthiiv 10′-ols 8 . Valenciaxanthin represents a modification of the common cleavage of carotenoids in higher plants according to the scheme C₄₀ → C₂₇ + C₁₃, insofar as the reduction step not only includes the aldehyde function but also the subsequent conjugated double bond.