Synthesis of optically active alicyclic polyimides from a chiral,nonracemic dianhydride

Optically active alicyclic polyimides were prepared for the first time from (?)‐[1S*,5R*,6S*]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(?)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (?)‐DAn was synthesized by an asymmetric Diels–Alder reaction of a chiral itaconic acid derivative as a key step. Colorless or slightly yellow flexible films were obtained for the (?)‐DAn‐derived polyimides {PI[(?)‐DAn]s}. PI[(?)‐DAn]s showed good solubility toward dipolar aprotic solvents and pyridine. For 1,4‐dioxane and chloroform, the optically active polyimides showed slightly better solubility than the corresponding polyimides prepared from rac‐DAn [PI(rac‐DAn)s]. PI[(?)‐DAn]s showed glass‐transition temperatures of 267–268 °C and 10% weight‐loss temperatures of 416–424 °C in nitrogen. These values were almost identical to those of PI(rac‐DAn)s. The circular dichroism spectra of PI[(?)‐DAn]s showed exciton coupling patterns indicating that to some extent these polyimides had a higher order structure in solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4038–4044, 2002     

Two androsterone derivatives as inhibitors of androgen biosynthesis

The title compounds, (3R,5S,5′R,8R,9S,10S,13S,14S)‐10,13‐dimethyl‐5′‐(2‐methylpropyl)tetradecahydro‐6′H‐spiro[cyclopenta[a]phenanthrene‐3,2′‐[1,4]oxazinane]‐6′,17(2H)‐dione, C₂₆H₄₁NO₃, (I), and methyl (2R)‐2‐[(3R,5S,8R,9S,10S,13S,14S)‐10,13‐dimethyl‐2′,17‐dioxohexadecahydro‐3′H‐spiro[cyclopenta[a]phenanthrene‐3,5′‐[1,3]oxazolidin‐3′‐yl]]‐4‐methylpentanoate, C₂₈H₄₃NO₅, (II), possess the typical steroid shape (A–D rings), but they differ in their extra E ring. The azalactone E ring in (I) shows a half‐chair conformation, while the carbamate E ring of (II) is planar. The orientation of the E‐ring substituent is clearly established and allows a rationalization of the biological results obtained with such androsterone derivatives.     

Reduction of Capsorubin and Cryptocapsin

(6′S)‐ and (6′R)‐‘Capsorubol‐6‐one' (=(3S,3′S,5R,5′R,6′S)‐ and (3S,3′S,5R,5′R,6′R)‐3,3′,6′‐trihydroxy‐κ,κ‐caroten‐6‐one; 8 and 9 , resp.), (6S,6′R)‐ and (6R,6′R)‐capsorubol (=3S,3′S,5R,5′R,6S,6′R)‐ and (3S,3′S,5R,5′R,6R,6′R)‐κ,κ‐carotene‐3,3′,6,6′‐tetrol; 11 and 12 , resp.) and (6′S)‐ and (6′R)‐cryptocapsol (=(3′S,5′R,6′S)‐ and (3′S,5′R,6′R)‐β,κ‐carotene‐3′,6′‐diol; 5 and 6 , resp.) were prepared in crystalline from by the reduction of capsorubin (=(3S,3′S,5R,5′R)‐3,3′‐dihydroxy‐κ,κ‐carotene‐6,6′‐dione; 7 ) and cryptocapsin (=(3′S,5′R)‐3′‐hydroxy‐β,κ‐caroten‐6′‐one; 4 ) and characterized by their UV/VIS, CD, ¹H‐NMR, and mass spectra.     

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.     

Further Prenylated Bi‐ and Tricyclic Phloroglucinol Derivatives from Hypericum papuanum

From the petroleum‐ether extract of the dried aerial parts of Hypericum papuanum, three new prenylated tricyclic and four new bicyclic acylphloroglucinol derivatives were isolated by bioactivity‐guided fractionation. The structures of the bicyclic compounds enaimeone A, B, and C ( 1 / 1a , 2 / 2a , and 3 / 3a , resp.) were elucidated as rel‐(1R,5R,6S)‐4‐hydroxy‐6‐(1‐hydroxy‐1‐methylethyl)‐5‐methyl‐1‐(3‐methylbut‐2‐enyl)‐3‐(2‐methylpropanoyl)‐bicyclo[3.2.1]oct‐3‐ene‐2,8‐dione ( 1 / 1a ), rel‐(1R,5R,6R)‐4‐hydroxy‐6‐(1‐hydroxy‐1‐methylethyl)‐5‐methyl‐1‐(3‐methylbut‐2‐enyl)‐3‐(2‐methylpropanoyl)bicyclo[3.2.1]oct‐3‐ene‐2,8‐dione ( 2 / 2a ), rel‐(1R,5R,6R)‐4‐hydroxy‐6‐(1‐hydroxy‐1‐methylethyl)‐5‐methyl‐3‐(2‐methylbutanoyl)‐1‐(3‐methylbut‐2‐enyl)bicyclo[3.2.1]oct‐3‐ene‐2,8‐dione ( 3 / 3a ). The tricyclic isolates 8‐hydroxy‐3β‐(1‐hydroxy‐1‐methylethyl)‐4,4,7‐trimethyl‐9‐(2‐methylpropanoyl)‐5βH‐tricyclo[5.3.1.0^1,5]undec‐8‐ene‐10,11‐dione ( 4 ), 8‐hydroxy‐3α‐(1‐hydroxy‐1‐methylethyl)‐4,4,7‐trimethyl‐9‐(2‐methylpropanoyl)‐5βH‐tricyclo[5.3.1.0^1,5]undec‐8‐ene‐10,11‐dione ( 5 ), and 8‐hydroxy‐3α‐(1‐hydroxy‐1‐methylethyl)‐4,4,7‐trimethyl‐9‐(2‐methylbutanoyl)‐5βH‐tricyclo[5.3.1.0^1,5]undec‐8‐ene‐10,11‐dione ( 6 ), and their corresponding tautomers 4a , 5a , and 6a , were named 1′‐hydroxyialibinones A, B, and D, respectively. Oxidative decomposition of furonewguinone A (=2,3,3a,5‐tetrahydro‐3a‐hydroxy‐2‐(1‐hydroxy‐1‐methylethyl)‐5‐methyl‐5‐(3‐methylbut‐2‐enyl)‐7‐(2‐methylpropanoyl)‐benzofuran‐4,6‐dione; 7 ) led to furonewguinone B (=3,3a,7,7a‐tetrahydro‐3a,6,7a‐trihydroxy‐2‐(1‐hydroxy‐1‐methylethyl)‐7‐methyl‐7‐(3‐methylbut‐2‐enyl)‐5‐(2‐methylpropanoyl)benzofuran‐4(2H)‐one; 8 / 8a ). Structure elucidation was based on extensive 1D and 2D NMR studies, as well as on data derived from mass spectrometry. Furthermore, the cytotoxicity towards KB nasopharyngeal carcinoma cells and the antibacterial activity were determined.     

Constitutionally isomeric alicyclic polyimides: Origin of siteselectivity in the reaction of unsymmetrical dianhydride and structure‐derived difference in physical properties

Two constitutionally isomeric alicyclic polyimides (PIs), head‐to‐head (HH) and random types, were successfully synthesized on the basis of a siteselective ring opening reaction of an unsymmetric spiroalicyclic dianhydride, rel‐[1R,5S,6R]‐3‐oxabicyclo[3,2,1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐2′,5′‐dione), with using several kinds of diamines only by changing reaction procedures. A model reaction study revealed that the origin of the siteselectivity in the reaction of the dianhydride was due to both the enhanced reactivity of six‐membered anhydride embedded in bicyclo[3.2.1] system and the reduced reactivity of five‐membered anhydride in the spiro[4.5] system. The HH‐PIs showed higher glass transition temperature and higher dielectric constant than those of random PIs. Specific gravity of the PI films showed that the differences in physical properties stem from different packing density of the two constitutionally isomeric PIs. This is the first example for constitutionally isomeric both amorphous polycondensates with different physical properties. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Precursors to dodecahedrane

The title compounds, (2R,2′′S,3b′S,4a′R,7b′S,8a′R)‐per­hydro­di­spiro­[furan‐2,3′‐di­cyclo­penta­[a,e]­pentalene‐7′,2′′‐furan]‐5,5′′‐dione, C₂₀H₂₆O₄, and (3aR,3bR,4aR,4bS,5aS,8aR,8bR,9aR,9bS,10aS)‐per­hydro­dipentaleno­[2,1‐a:2′,1′‐e]­pentalene‐1,6‐dione, C₂₀H₂₆O₂, are intermediates identified during the synthesis of dodecahedrane. Crystallographic studies have established the ring‐junction stereochemistry for these important intermediates. All the ring junctions are cis‐fused, and the molecular packing is stabilized by van der Waals interactions.     

Breaking the Mirror: pH‐Controlled Chirality Generation from a meso Ligand to a Racemic Ligand

To study the conversion from a meso form to a racemic form of tetrahydrofurantetracarboxylic acid (H₄L), seven novel coordination polymers were synthesized by the hydrothermal reaction of Zn(NO₃)₂ ? 6 H₂O with (2S,3S,4R,5R)‐H₄L in the presence of 1,10‐phenanthroline (phen), 2,2′‐bipyridine (2,2′‐bpy), or 4,4′‐bipyridine (4,4′‐bpy): [Zn₂{(2S,3S,4R,5R)‐L}(phen)₂(H₂O)] ? 2 H₂O ( 1 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L}(phen)₂(H₂O)₂] ( 2 ), [Zn₂{(2S,3S,4R,5R)‐L}(H₂O)₂] ? H₂O ( 3 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L} (2,2′‐bpy)₂(H₂O)₂] ? 2 H₂O ( 4 ), [Zn₂ {(2S,3S,4R,5R)‐L}(2,2′‐bpy)(H₂O)] ( 5 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L} (4,4′‐bpy)₂(H₂O)₂] ( 6 ), and [Zn₂ {(2S,3S,4R,5R)‐L}(4,4′‐bpy)(H₂O)] ? 2 H₂O ( 7 ). These complexes were obtained by control of the pH values of reaction mixtures, with an initial of pH 2.0 for 1 , 2.5 for 2 , 4 , and 6 , and 4.5 for 3 , 5 , and 7 , respectively. The expected configuration conversion has been successfully realized during the formation of 2 , 4 , and 6 , and the enantiomers of L, (2S,3R,4R,5R)‐L and (2S,3S,4S,5R)‐L, are trapped in them, whereas L ligands in the other four complexes retain the original meso form, which indicates that such a conversion is possibly pH controlled. Acid‐catalyzed enol–keto tautomerism has been introduced to explain the mechanism of this conversion. Complex 1 features a simple 1D metal–L chain that is extended into a 3D supramolecular structure by π–π packing interactions between phen ligands and hydrogen bonds. Complex 2 has 2D racemic layers that consist of centrosymmetric bimetallic units, and a final 3D supramolecular framework is formed by the interlinking of these layers through π–π packing interactions of phen. Complex 3 is a 3D metal–organic framework (MOF) involving meso‐L ligands, which can be regarded as (4,6)‐connected nets with vertex symbol (4⁵.6)(4⁷.6⁸). Complexes 4 and 5 contain 2D racemic layers and (6,3)‐honeycomb layers, respectively, both of which are combined into 3D supramolecular structures through π–π packing interactions of 2,2′‐bpy. The structure of complex 6 is a 2D network formed by 4,4′‐bpy bridging 1D tubes, which consist of metal atoms and enantiomers of L. These layers are connected through hydrogen bonds to give the final 3D porous supramolecular framework of 6 . Complex 7 is a 3D MOF with novel (3,4,5)‐connected (6³)(4².6⁴)(4².6⁶.8²) topology. The thermal stability of these compounds was also investigated.     

Non‐iterative Asymmetric Synthesis of C15 Polyketide Spiroketals

The 2,2′‐methylenebis[furan] ( 1 ) was converted to 1‐{(4R,6S))‐6‐[(2R)‐2,4‐dihydroxybutyl]‐2,2‐dimethyl‐1,3‐dioxan‐4‐yl}‐3‐[(2R,4R)‐tetrahydro‐4,6‐dihydroxy‐2H‐pyran‐2‐yl)propan‐2‐one ((+)‐ 18 ) and its (4S)‐epimer (?)‐ 19 with high stereo‐ and enantioselectivity (Schemes 1–3). Under acidic methanolysis, (+)‐ 18 yielded a single spiroketal, (3R)‐4‐{(1R,3S,4′R,5R,6′S,7R)‐3′,4′,5′,6′‐tetrahydro‐4′‐hydroxy‐7‐methoxyspiro[2,6‐dioxabicyclo[3.3.1]nonane‐3,2′‐[2H]pyran]‐6′‐yl}butane‐1,3‐diol ((?)‐ 20 ), in which both O‐atoms at the spiro center reside in equatorial positions, this being due to the tricyclic nature of (?)‐ 20 (methyl pyranoside formation). Compound (?)‐ 19 was converted similarly into the (4′S)‐epimeric tricyclic spiroketal (?)‐ 21 that also adopts a similar (3S)‐configuration and conformation. Spiroketals (?)‐ 20 , (?)‐ 21 and analog (?)‐ 23 , i.e., (1R,3S,4′R,5R,6′R)‐3′,4′,5′,6′‐tetrahydro‐6′‐[(2S)‐2‐hydroxybut‐3‐enyl]‐7‐methoxyspiro[2,6‐dioxabicyclo[3.3.1]nonane‐3,2′‐[2H]pyran]‐4′‐ol, derived from (?)‐ 20 , were assayed for their cytotoxicity toward murine P388 lymphocytic leukemia and six human cancer cell lines. Only racemic (±)‐ 21 showed evidence of cancer‐cell‐growth inhibition (P388, ED₅₀: 6.9 μg/ml).     

Plumeridoid C from the Amazonian traditional medicinal plant Himatanthus sucuuba

The stereochemistry of the iridoid plumeridoid C, C₁₅H₁₈O₇, was established by X‐ray single‐crystal structure analysis, giving (2′R,3R,4R,4aS,7aR)‐methyl 3‐hydroxy‐4′‐[(S)‐1‐hydroxyethyl]‐5′‐oxo‐3,4,4a,7a‐tetrahydro‐1H,5′H‐spiro[cyclopenta[c]pyran‐7,2′‐furan]‐4‐carboxylate. The absolute structure of the title compound was determined on the basis of the Flack x parameter and Bayesian statistics on Bijvoet differences. The hydrogen‐bond donor and acceptor functions of the two hydroxy groups are employed in the formation of O—H...O‐bonded helical chains.     

Green synthesis and crystal structure of 4,7‐diaryl‐2‐oxo(thio)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐5‐one derivatives

A green and convenient approach to the synthesis of novel 4,7‐diaryl‐2‐oxo(thio)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐5‐one derivatives from appropriate aromatic aldehydes and 5‐aryl‐1,3‐cyclohexanedione with urea or thiourea in the presence of dilute HCl as catalyst in water is described. This method provides several advantages such as environmental friendliness, low cost, high yields, and simple workup procedure. The structures of all compounds were characterized by elemental analysis, IR, MS, and ¹H NMR. The crystal and molecular structure of 4‐(4′‐chlorophenyl)‐7‐(4′‐methoxyphenyl)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐2,5‐dione 5m have been determined by single crystal X‐ray diffraction analysis. The crystal of compound 5m belongs to monoclinic with space group P‐2₁/c, a = 1.4353 (4) nm, b = 1.4011 (4) nm, c = 0.9248 (3) nm, α = 90.00°, β = 101.242 (6)°, γ = 90.00°, Z = 4, V = 1.8241 (9) nm³, R₁ = 0.0448, and wR₂ = 0.1022. J. Heterocyclic Chem., (2011).     

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.     

Synthesis,Structure, and Conformation of 2′,3′‐Fused Oxathiane and Thiomorpholine Uridines

The syntheses of two 2′,3′‐fused bicyclic nucleoside analogues, i.e., 1‐[(4aR,5R,7R,7aS)‐hexahydro‐5‐(hydroxymethyl)‐4,4‐dioxidofuro[3,4‐b][1,4]oxathiin‐7‐yl]pyrimidine‐2,4(1H,3H)‐dione ( 1a ) and 1‐[(4aS,5R,7R,7aS)‐hexahydro‐7‐(hydroxymethyl)‐1,1‐dioxido‐2H‐furo[3,4‐b][1,4]thiazin‐5‐yl]pyrimidine‐ 2,4(1H,3H)‐dione ( 1b ), are described, the key step being an intramolecular hetero‐Michael addition. Their structures and conformations, previously solved by X‐ray crystallography, were analyzed in more detail, using 1D‐ and 2D‐NMR as well as HR‐MS analyses.     

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.     

Characterization,crystal structure and cytotoxic activity of a rare iridoid glycoside from Lonicera saccata

A new iridoid glycoside, methyl (3R,4R,4aS,7S,7aR)‐3‐hydroxy‐7‐methyl‐5‐oxooctahydrocyclopenta[c]pyran‐4‐carboxylate‐3‐O‐β‐d ‐(1′S,2′R,3′S,4′S,5′R)‐glucopyranoside, named loniceroside A, C₁₇H₂₆O₁₀, ( 1 ), was obtained from the aerial parts of Lonicera saccata. Its structure was established based on an analysis of spectroscopic data, including 1D NMR, 2D NMR and HRESIMS, and the configurations of the chiral C atoms were determined by X‐ray crystallographic analysis. The single‐crystal structure reveals that the cyclopenta[c]pyran scaffold is formed from a five‐membered ring and a chair‐like six‐membered ring connected through two bridgehead chiral C atoms. In the solid state, the glucose group of ( 1 ) plays an important role in constructing an unusual supramolecular motif. The structure analysis revealed adjacent molecules linked together through intermolecular O—H…O hydrogen bonds to generate a banded structure. Furthermore, the banded structures are linked into a three‐dimensional network by interesting hydrogen bonds. Biogenetically, compound ( 1 ) carries a glucopyranosyloxy moiety at the C‐3 position, representing a rare structural feature for naturally occurring iridoid glycosides. The growth inhibitory effects against human cervical carcinoma cells (Hela), human lung adenocarcinoma cells (A549), human acute mononuclear granulocyte leukaemia (THP‐1) and the human liver hepatocellular carcinoma cell line (HepG2) were evaluated by the MTT method.     

Diarylheptanoids from the Rhizomes of Alpinia officinarum

A novel dimeric diarylheptanoid, (5R,5′R)‐7,7′‐(6,6′‐dihydroxy‐5,5′‐dimethoxy[1,1′‐biphenyl]‐3,3′‐diyl)bis[5‐methoxy‐1‐phenylheptan‐3‐one] ( 1 ), and two new diarylheptanoids, (4E,6R)‐6‐hydroxy‐7‐(4‐hydroxy‐3‐methoxyphenyl)‐1‐phenylhept‐4‐en‐3‐one ( 2 ) and (4E,6R)‐6‐hydroxy‐1,7‐diphenylhept‐4‐en‐3‐one ( 3 ), together with seven known diarylheptanoids, were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by application of extensive spectroscopic analyses and the modified Mosher method.     

Facile Chemoselective synthesis of 2‐(2‐(Methoxycarbonyl)‐3‐oxo‐2,3‐dihydrobenzofuran‐2‐yl)benzoic acids and 3H,3’H‐Spiro[benzofuran‐2,1′‐isobenzofuran]‐3,3′‐dione derivatives

Oxidation of some derivatives of 4b,9b–dihydroxyindeno[1,2‐b]benzofuran‐10‐one have been investigated in detail using lead(IV) acetate in acetic acid under reflux conditions and periodic acid in aqueous ethanol at room temperature. We realized that during the first 5–15 minutes of the oxidation reactions in lead(IV) acetate/acetic acid system, 3H,3’H‐spiro[benzofuran‐2,1′‐isobenzofuran]‐3,3′‐dione derivatives have been synthesized chemo selectively, while, if the reaction mixtures stirred for additional 3 hours, the main products would be 2‐(2‐(Methoxycarbonyl)‐3‐oxo‐2,3‐dihydrobenzofuran‐2‐yl)benzoic acids. Moreover, room temperature oxidation of 4b,9b–dihydroxyindeno[1,2‐b]benzofuran‐10‐ones by periodic acid (H₅IO₆), leads to the formation of 3H,3’H‐spiro[benzofuran‐2,1′‐isobenzofuran]‐3,3′‐dione derivatives in good to excellent yields.     

Ferroelectric liquid crystals induced by dopants with axially chiral 2,2′‐spirobiindan‐1,1′‐dione cores: diether vs. diester side‐chains

A series of axially chiral 5,5′‐ and 6,6′‐dialkanoyloxy‐2,2′‐spirobiindan‐1,1′‐dione dopants, (R)‐2 and (R)‐4a–4c were synthesized in optically pure form and their ferroelectric polarization powers, δ_p, measured in four liquid crystal hosts with isotropic (I)–nematic (N)–smectic A (SmA)–smectic C (SmC) phase sequences. The results show that the sign of polarization P _S induced by (R)‐2 and (R)‐4a–4c follows the same trend as that previously reported for the 5,5′‐ and 6,6′‐diheptyloxy‐2,2′‐spirobiindan‐1,1′‐dione dopants, (R)‐1 and (R)‐3. The polarization induced by (R)‐2 in the host DFT is below detection limits, and the sign of P _S was found to invert as a function of temperature at mole fractions as low as 0.01. On the other hand, the polarization power of the 6,6′‐diheptanoyloxy dopant (R)‐4b in the host NCB76 is ?1449 nC cm^?2, the fourth highest value reported so far, and more than three times the δ_p value of the 5,5′‐diheptanoyloxy analogue (R)‐2 in that host (+474 nC cm^?2). Results of ²H NMR experiments suggest that (R)‐4b exerts stronger local perturbations in NCB76 than (R)‐2, and that these perturbations may be chiral in nature.     

Absolute structures and conformations of the spongian diterpenes spongia‐13(16),14‐dien‐3‐one,epispongiadiol and spongiadiol

The absolute configurations of spongia‐13(16),14‐dien‐3‐one [systematic name: (3bR,5aR,9aR,9bR)‐3b,6,6,9a‐tetramethyl‐4,5,5a,6,8,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐7(3bH)‐one], C₂₀H₂₈O₂, (I), epispongiadiol [systematic name: (3bR,5aR,6S,7R,9aR,9bR)‐7‐hydroxy‐6‐hydroxymethyl‐3b,6,9a‐trimethyl‐3b,5,5a,6,7,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐8(4H)‐one], C₂₀H₂₈O₄, (II), and spongiadiol [systematic name: (3bR,5aR,6S,7S,9aR,9bR)‐7‐hydroxy‐6‐hydroxymethyl‐3b,6,9a‐trimethyl‐3b,5,5a,6,7,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐8(4H)‐one], C₂₀H₂₈O₄, (III), were assigned by analysis of anomalous dispersion data collected at 130 K with Cu Kα radiation. Compounds (II) and (III) are epimers. The equatorial 3‐hydroxyl group on the cyclohexanone ring (A) of (II) is syn with respect to the 4‐hydroxymethyl group, leading to a chair conformation. In contrast, isomer (III), where the 3‐hydroxyl group is anti to the 4‐hydroxymethyl group, is conformationally disordered between a major chair conformer where the OH group is axial and a minor boat conformer where it is equatorial. In compound (I), a carbonyl group is present at position 3 and ring A adopts a distorted‐boat conformation.     

2′,3′‐Dehydrosalannol

The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodeca­hydro‐3‐hydroxy‐2a,5a,6a,7‐tetra­methyl‐5‐(3‐methylbut‐2‐enoyl­oxy)‐2H,3H‐cyclo­penta­[4′,5′]­furo­[2′,3′:6,5]benzo[cd]­isobenzo­furan‐6‐acetate, C₃₂H₄₂O₈, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐des­acetyl­salannin, which was isolated from neem kernels. The mol­ecules are linked into chains by intermolecular O—H?O hydrogen bonds.