Benzimidazolium quaternary ammonium salts: synthesis, single crystal and Hirshfeld surface exploration supported by theoretical analysis

Owing to the broad applications of quaternary ammonium salts (QAS), we present the synthesis of benzimidazolium-based analogues with variation in the alkyl and alkoxy group at N-1 and N-3 positions. All the compounds were characterized by spectroscopic techniques and found stable to air and moisture both in the solid and solution state. Moreover, molecular structures were established through single-crystal X-ray diffraction studies. The crystal packing of the compounds was stabilized by numerous intermolecular interactions explored by Hirshfeld surface analysis. The enrichment ratio was calculated for the pairs of chemical species to acquire the highest propensity to form contacts. Void analysis was carried out to check the mechanical response of the compounds. Furthermore, theoretical investigations were also performed to explore the optoelectronic properties of compounds. Natural population analysis (NPA) has been conducted to evaluate the distribution of charges on the synthesized compounds, whereas high band gaps of the synthesized compounds by frontier molecular orbital (FMO) analysis indicated their stability. Nonlinear optical (NLO) analysis revealed that the synthesized QAS demonstrates significantly improved NLO behaviour than the standard urea.

Evaluation of Antimicrobial, Anticholinesterase Potential of Indole Derivatives and Unexpectedly Synthesized Novel Benzodiazine: Characterization, DFT and Hirshfeld Charge Analysis

The pharmacological effectiveness of indoles, benzoxazepines and benzodiazepines initiated our synthesis of indole fused benoxazepine/benzodiazepine heterocycles, along with enhanced biological usefulness of the fused rings. Activated indoles 5, 6 and 7 were synthesized using modified Bischler indole synthesis rearrangement. Indole 5 was substituted with the trichloroacetyl group at the C⁷ position, yielding 8, exclusively due to the increased nucleophilic character of C⁷. When trichloroacylated indole 8 was treated with basified ethanol or excess amminia, indole acid 9 and amide 10 were yielded, respectively. Indole amide 10 was expected to give indole fused benoxazepine/benzodiazepine 11a/11b on treatment with alpha halo ester followed by a coupling agent, but when the reaction was tried, an unexpectedly rearranged novel product, 1,3-bezodiazine 12, was obtained. The synthetic compounds were screened for anticholinesterase and antibacterial potential; results showed all products to be very important candidates for both activities, and their potential can be explored further. In addition, 1,3-bezodiazine 12 was explored by DFT studies, Hirshfeld surface charge analysis and structural insight to obrain a good picture of the structure and reactivity of the products for the design of derivatised drugs from the novel compound.

Synthesis, Crystal Structure, DFT Calculations, Hirshfeld Surface Analysis and In Silico Drug-Target Profiling of (R)-2-(2-(1,3-Dioxoisoindolin-2-yl)propanamido)benzoic Acid Methyl Ester

The work here reflects synthesis, DFT studies, Hirshfeld charge analysis and crystal data exploration of pharmacologically important (R)-2-(2-(1,3-dioxoisoindolin-2-yl)propanamido)benzoic acid methyl ester (5) to understand its properties for further chemical transformations. The methyl anthranilate (2) was produced by the esterification of anthranilic acid in an acidic medium. The phthaloyl-protected alanine (4) was rendered by the fusion of alanine with phthalic anhydride at 150 °C, followed by coupling with (2) furnished isoindole (5). The characterization of products was performed using IR, UV-Vis, NMR and MS. Single-crystal XRD also verified the structure of (5) in which N-H⋯O bonding stabilizes the molecular configuration of (5), resulting in the formation of S(6) hydrogen-bonded loop. The molecules of isoindole (5) are connected in the form of dimers, and the π⋯π stacking interaction between aromatic rings further stabilizes the crystal packing. DFT studies suggest that HOMO is over the substituted aromatic ring, the LUMO is present mainly over the indole side, and nucleophilic and electrophilic corners point out the reactivity of the product (5). In vitro and in silico analysis of (5) shows its potential as an antibacterial agent targeting DNA gyrase and Dihydroorotase from E. coli and tyrosyl-tRNA synthetase and DNA gyrase from Staphylococcus aureus.

Synthesis, characterization, and in vitro anti-cholinesterase screening of novel indole amines

The present study involved the targeted synthesis and characterization of novel indole amines with anti-acetylcholinesterase profiling. A series of proposed indole amines was virtually screened against human acetylcholinesterase. A few indole amines (23, 24, and 25) showing strong enzyme binding in the in silico studies were synthesized in the laboratory and characterized using spectroscopic (IR, UV, NMR, single crystal XRD) and spectrometric (EIMS, HR-EIMS) methods. The indole amine 23 was crystallized from EtOH and analyzed with single crystal XRD. These ligands interacted with the PAS site in the enzyme, and their binding may disrupt the activity. The in vitro acetylcholinesterase inhibition studies revealed that the IC₅₀ values for indole amines 25 and 24 (4.28 and 4.66 μM, respectively) were comparable to that of galantamine (4.15 μM) and may be studied further as cost-effective acetylcholinesterase inhibitors.

Characterization and anticancer potential of Withania somnifera fruit bioactives (a native species to Pakistan) using gas chromatography-mass spectrometer, nuclear magnetic resonance and liquid chromatography-mass spectrometry-electrospray ionization

INTRODUCTION

Withania somnifera (W. somnifera) is a plant with remarkable pharmacological properties. The plant has an impressive profile of medicinal uses in the folk medicine system of several civilizations.

AIM

This comprehensive study is aimed to characterize phytochemicals in fruit of W. somnifera and tested for anticancer potential to find out active candidate in disease prevention and treatment.

METHODS

The bioactive components from W. somn-ifera fruit were extracted with polar and non-polar solvents. Anticancer potential of the isolated bioactive was assessed against different cancer cell lines through MTT assay and Incucytes imaging analysis. The extracts were characterized for secondary metabolites using GC-MS (gas chromatography-mass spectrometer), LCMS (liquid chromatography-mass spectrometry)-ESI (electrospray Ionization) and 1H-NMR (electrospray Ionization) techniques.

RESULTS

Both freeze-dried and rotary evaporator con-densed extracts exhibited anticancer potential against MDA-MB-231, MCF7- SKOV3 and SKBR3 cell lines. The tested extracts have cell growth inhibition potential ag-ainst mammalian cancer cell line. Hexacosanedioic acid purified from -hexane extract through HPLC was inves-tigated for its cytotoxicity against breast cancer cell line SKBR3 by using Incucytes imaging analysis.

CONCLUSION

We found that a variety of bioactive compounds existed in this plant. One identified compound that was not investigated for cytotoxicity in previous studies was purified and its application showed cytotoxicity on breast cancer cell lines. A number of bioactive identified from fruit may have an effective potential for development into chemotherapy drugs.

Synthesis and evaluation of 2-phenylamino-1,4-naphthoquinones derivatives as potential hypoglycaemic agents

Due to the severe side effects revealed by most of the currently used antidiabetic medicines, search for finding new and safe drugs to manage diabetes is continued. Naphthoquinones possessing strong antioxidant properties have been employed as candidates for diabetes therapy. Present study is aimed at finding the antioxidant and hypoglycaemic potential of some novel derivatives of 2-phenylamino-1,4-naphthoquinones (PAN) including chloro, nitro, methyl and bromo (5a-d) derivatives synthesized by single pot experiment. Product crystals were purified by TLC and characterized by FT-IR. The antioxidant potential of the compounds was assayed through DPPH radical scavenging and reducing power activities noted as UV-vis. absorbance. The DPPH assay has showed the powerful antioxidant activity of nitro and bromo derivatives, while the nitro derivative showed the significant reduction potential towards FRAP assay. Hypoglycaemic potential of the compounds was studied in rat animal model. All synthesized compounds revealed better hypoglycaemic activity; however, the chloro-derivative exhibited the more potent hypoglycaemic activity showing about 43% reduction in the mean blood glucose levels of the treated animals. As the bioreduction of naphthoquinones may be influenced by changing its redox properties, it has been noticed that the e-donating resonance effect (+R) of 'chloro' group has shown the significant effects on biological activity through stabalization of its imine form which limits the potential of generation of free radicals during bioreduction of quinones and thus has been proposed as the reason of its hypoglycaemic activity. Future studies employing the properties of e-donating groups of PAN may optimize the drug-receptor interaction for better drug designing and drug development strategies against diabetes and also for the clinical trials.

GC-MS Metabolomics profiling and HR-APCI-MS characterization of potential anticancer compounds and antimicrobial activities of extracts from Picrorhiza kurroa roots

The present study explores pharmacological potential and phytochemicals profiling of Picrorhiza kurroa extracts against mammalian cancer cell lines and pathogenic microbes. Bioactive extracts from roots of Picrorhiza kurroa were recovered in the methanol, 50% aqueous dichloromethane (50 : 50 v/v) and n-hexane. Antimicrobial activity of the bioactive extracts was assessed against selected strains of bacteria and pathogenic fungi. Aqueous dichloromethane extract showed highest zone of growth inhibition (39.06 ± 1.0 mm) towards Staphylococcus aureus bacteria while methanolic extract showed the lowest inhibition (6.3 ± 4.1 mm) to Escherichia coli bacteria. The tested extracts such as methanol and aqueous dichloromethane exhibited higher inhibition antifungal activity against Aspergillus flavus compared to Fusarium oxysporum. As far as cytotoxicity (MTT assay) of the tested extracts is concerned, n-hexane and aqueous dichloromethane extracts were found to be very active against all cancer cell lines (breast cancer MCF7, MDA-MB-231, SKBR3 and ovarian cancer SKOV3). A preliminary phytochemicals profiling was performed in extracts using GC-MS. Several fractions of active extract were separated with HPLC and analyzed using High Resolution Atmospheric Pressure Chemical Ionization Mass Spectrometry (HR-APCI-MS). Two purified compounds (Dihydromikanolide and 1,3-Dicyclohexyl-4-(cyclohexylimino)-2-(cyclohexylethylamino)-3,4-dihydro-1,3-diazetium) were further evaluated for their anticancer activity against ovarian cancer cell line. Our findings depict that all the tested extracts showed considerable anticancer potential through cell viability assays. The purified compound 1 - Dihydromikanolide from methanolic extract was found to be active against ovarian cancer cells and can be explored as a promising nutra-pharmaceutical candidate against ovarian cancer. However, further studies exploring the molecular pathways and in vivo testing are required.

Facile Synthesis of Diversely Functionalized Peptoids, Spectroscopic Characterization, and DFT-Based Nonlinear Optical Exploration

Compounds having nonlinear optical (NLO) characteristics have been proved to have a significant role in many academic and industrial areas; particularly, their leading role in surface interfaces, solid physics, materials, medicine, chemical dynamics, nuclear science, and biophysics is worth mentioning. In the present study, novel peptoids (1-4) were prepared in good yields via Ugi four-component reaction (Ugi-4CR). In addition to synthetic studies, computational calculations were executed to estimate the molecular electrostatic potential, natural bond orbital (NBO), frontier molecular orbital analysis, and NLO properties. The NBO analysis confirmed the stability of studied systems owing to containing intramolecular hydrogen bonding and hyperconjugative interactions. NLO analysis showed that investigated molecules hold noteworthy NLO response as compared to standard compounds that show potential for technology-related applications.

In Vitro Antioxidant Activities and the Therapeutic Potential of Some Newly Synthesized Chalcones Against 4-Acetaminophenol Induced Hepatotoxicity in Rats

The lack of safety and efficacy of existing hepatoprotective agents urge the need to explore novel hepatoprotective agents. The research work was planned to study the therapeutic potential of some newly synthesized chalcones against 4-acetaminophenol induced hepatotoxicity in rats. Male albino rats (N = 30) were divided into 6 groups of 5 animals each i.e. group I; Toxic control (4-acetaminophenol), group II; normal control (Normal saline), group III; Positive control (silymarin; 50 mg/kg bw) and groups IV-VI (test groups) treated with 3 chalcone analogues i-e 3a, 3f & 3 g (100, 150, 150 mg/kg bw, respectively). All the study group animals were administered with 4-acetaminophenol to induce hepatotoxicity except normal control. Following hepatotoxicity induction, test group animals were administered with selected doses of test compounds and toxic group animals left untreated. Liver enzymes including ALT, AST, ALP and serum bilirubin were determined photometrically. Antioxidant activities of test compounds were also determined. Histopathological examination of liver biopsies was also carried out through H & E staining. The test chalcones (3a, 3f & 3 g) significantly decreased the levels of liver enzymes and serum bilirubin toward normal and the pattern of results in the test group animals were comparable to silymarin administered animals indicating the hepatoprotective potential of test compounds. Moreover, the test chalcones (3a, 3f & 3 g) antagonized the effect of 4-acetaminophenol and thus, raised the catalase (CAT) and superoxide dismutase (SOD) while decreased the malondialdehyde (MDA) in experimental animals. The test chalcones (3a, 3f & 3 g) on histological examination of liver showed improvement of tissue morphology. The study concluded that the tested compounds have antioxidant potential and may act as hepatoprotective agent. However, in-depth studies are required to validate their safety and to elucidate the exact mechanism of action.

Synthesis, Characterization and Anti-Cancer Therapeutic Potential of Withanolide-A with 20nm sAuNPs Conjugates Against SKBR3 Breast Cancer Cell Line

Background

Nanotechnology is gaining emerging interest in advanced drug discovery therapeutics due to their tremendous properties including enhanced delivery of therapeutic payload, extensive surface to volume ratio, high permeability, retention behaviors, etc. The gold nanoparticles (AuNPs) are favored due to their advanced features, such as biogenic, tunable physiochemical response, ease in synthesis, and wide range of biomedical applications. The phytochemicals have been focused to design Au nano-carrier-based conjugation for active-targeting drug delivery due to their nano conjugation ability.

Aim

The present study describes the facile synthesis of 20nm spherical AuNPs and their conjugation with reported anti-cancer phytocompound Withanolide-A (1).

Methods

The 20nm sAuNPs were synthesized chemically and characterized their phytochemical gold nanoconjugates through UV-visible spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM) imaging techniques. The anti-cancer therapeutic potentials were tested with both nanoconjugates and pure WithanolideA (1) by using SKBR3 breast cancer cells line.

Results

The synthesized sAuNPs showed significant conjugation with Withanolide-A and showed stability. Furthermore, these Au nanoconjugates with Withanolide-A (1) significantly induce blockage of SKBR3 cell growth at half maximal active concentration that compared to pure Withanolide-A (1).

Conclusion

Our findings provide a foundation to further progress how they can overcome cancer drug resistance by conjugating active drugs in combination with AuNPs through optimizing the effective drug concentration and removing the surface barrier.

A facile microwave assisted synthesis and structure elucidation of (3R)-3-alkyl-4,1-benzoxazepine-2,5-diones by crystallographic, spectroscopic and DFT studies

The use of microwave (MW) irradiation in organic synthesis has become increasingly popular within the pharmaceutical and academic arenas because it is a new enabling technology for drug discovery and development. It is a rapid way of synthesis, which involves faster reaction rates and high selectivity to conventional heating method of syntheses. The MW-assisted 7-exo-tet cyclization of N-acylanthranilic acids afforded (3R)-3-alkyl-4,1-benzoxazepines-2,5-diones in very short duration (20 min) with extraordinary high yields in comparison to conventional heating mode of synthesis. The method development, comparative yields of MW-assisted and thermal method of syntheses, crystallographic, spectroscopic and density functional theory (DFT) studies are reported herein. Four novel compounds with chemical formulas C₁₀H₉BrClNO₃5m, C₁₉H₁₉NO₃6e, C₁₃H₁₄ClNO₃6h and C₁₂H₁₁Br₂NO₃6h were synthesized, validated by ¹HNMR, ¹³CNMR, FT-IR, UVVis, EIMS spectroscopic techniques and confirmed by using single crystal X-ray diffraction (SC-XRD) study. The DFT and TDDFT calculations at B3LYP/6-311 + G(d,p) level of theory were performed for comparative analysis of spectroscopic data, optimized geometries, frontier molecular orbitals (FMOs), natural bond orbital (NBO) analysis and nonlinear optical (NLO) properties of 5m, 6e, 6h and 6o. Overall, experimental findings were supported nicely by corresponding DFT computed results. The NBO analysis confirmed that the presence of non-covalent interactions, hydrogen bonding and hyper- conjugative interactions are pivotal cause for the existence of 5m, 6e, 6h and 6o in the solid-state. NLO analysis showed that 5m, 6e, 6h and 6o have significant NLO properties as compared to prototype standard compound which disclosed their potential for technology related applications.

Nucleophilic phenylation: a remarkable application of alkoxymethyltriphenylphosphonium salts

A new application of α-alkoxymethylphosphonium salts in the nucleophilic phenylation of carbonyl compounds is demonstrated. Phenylation of aldehydes, ketones and acyl halides were studied by employing α-alkoxymethyltriphenylphosphonium halides in the presence of lithium hydroxide. New application of α-alkoxymethyltriphenylphosphonium salts. Metal-free, mild and selective phenylation. Easy preparation and handling of the reagent.

An efficient protocol for the synthesis of highly sensitive indole imines utilizing green chemistry: optimization of reaction conditions

Novel and highly sensitive indole-based imines have been synthesized. Their synthesis has been compared employing a variety of protocols. Ultimately, a convenient, economical and high yielding set of conditions employing green chemistry have been designed for their synthesis.

Asymmetric synthesis of 4,1-benzoxazepine-2,5-diones--effect of the halogen of (2S)-α-haloacids

Novel chiral 4,1-benzoxazepine-2,5-diones have been unusually synthesized in a single step by exploiting the chiral pool methodology. Substituted anthranilic acids afford N-acylanthranilic acids and (3R)-3-alkyl-4,1-benzoxazepines-2,5-dione upon coupling with α-chloroacids or α-bromoacids, respectively.

Evaluation of silica-H2SO4 as an efficient heterogeneous catalyst for the synthesis of chalcones

We report an efficient silica-H₂SO₄ mediated synthesis of a variety of chalcones that afforded the targeted compounds in very good yield compared to base catalyzed solvent free conditions as well as acid or base catalyzed refluxing conditions.

4-Chloro-2-hydroxy-N-(4-methylphenyl)benzamide

In the title compound, C₁₄H₁₂ClNO₂, the dihedral angle between the aromatic rings is 14.87 (11)° and an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, generating C(6) chains propagating along the c-axis direction.

2-Hydroxy-N-(4-methylphenyl)benzamide

In the crystal structure of the title compound, C₁₄H₁₃NO₂, the mol­ecules are approximately planar, the r.m.s. deviation for all non-H atoms being 0.0435 Å; the dihedral angle between the two rings is 3.45 (12)°. The planarity is accounted for in terms of the presence of intra­molecular N—H⋯O and C—H⋯O hydrogen bonding, each of which completes an S(6) ring motif. The mol­ecules are stabilized in the form of supra­molecular chains extending along the crystallographic c axis due to inter­molecular O—H⋯O and C—H⋯O hydrogen bonding; each type leads to an R₂¹(6) ring motif.

(2R)-2-(1,3-Dioxoisoindolin-2-yl)-3-methyl-butanoic acid

In the title compound, C₁₃H₁₃NO₄, the dihedral angle between the nine-membered phthalimino ring system and the carb­oxy­lic acid group is 67.15 (9)°. An intra­molecular C—H⋯O close contact, which forms an S(6) ring, may help to establish the mol­ecular conformation. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, thereby forming C(7) chains propagating in [010].

2,4-Dinitro-1-naphthol

In the title compound, C₁₀H₆N₂O₅, the two fused rings are almost co-planar, with an r.m.s. deviation of 0.0163 Å. The nitro groups are oriented at dihedral angles of 2.62 (11) and 44.69 (11)° with respect to the plane of the parent fused rings. Intra­molecular O—H⋯O and C—H⋯O hydrogen bonds complete S(6) ring motifs. In the crystal, mol­ecules are linked into chains along [101] by inter­molecular O—H⋯O hydrogen bonds. π–π inter­actions [centroid–centroid distances = 3.6296 (15), 3.8104 (15) and 3.6513 (14) Å] might play a role in stabilizing the structure.

2-(2-Oxothio-lan-3-yl)isoindoline-1,3-dione

In the title compound, C₁₂H₉NO₃S, the isoindoline-1,3-dione group is almost planar, with an r.m.s. deviation of 0.020 Å, whereas the heterocyclic ring approximates to an envelope with the methyl­ene group not adjacent to the S atom in the flap position. A short intra­molecular C—H⋯O contact generates an S(6) ring motif. In the crystal structure, weak aromatic π–π stacking inter­actions occur between the centroids of the benzene rings at a distance of 3.558 (2) Å.

5-Chloro-2-hy-droxy-benzoic acid

The asymmetric unit of the title compound, C₇H₅ClO₃, contains two mol­ecules; both feature an intra­molecular O—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, both mol­ecules form inversion dimers linked by pairs of O—H⋯O hydrogen bonds with R₂²(8) ring motifs. The dimers are inter­linked by C—H⋯O inter­actions.

2-Hydroxy-N-(3-nitrophenyl)benzamide

In the crystal structure of title compound, C₁₃H₁₀N₂O₄, as expected, the nitro- and hy­droxy-substituted benzene rings are planar with r. m. s. deviations of 0.0037 and 0.0014 Å, respectively, but are twisted slightly relative to each other, making a dihedral angle of 12.23 (7)°. The nitro group is only slightly twisted [by 2.71 (16)°] with respect to its parent ring. An intra­molecular N—H⋯O hydrogen bond forms an S(6) ring motif. Inter­molecular N—H⋯O and O—H⋯O hydrogen bonds build up sheets parallel to the ab plane. Futhermore, weak π–π inter­actions [centroid–centroid distances = 3.7150 (8) 3.7342 (6) and 3.9421 (8) Å] between the rings yield a three-dimensional network.

2-Hy-droxy-5-nitro-N-phenyl-benzamide

The mol-ecule of the title compound, C(13)H(10)N(2)O(4), is almost planar with a dihedral angle between the benzene rings of 1.99 (13)°. The nitro group and its parent benzene ring are oriented at a dihedral angle of 7.6 (3)°. Intra-molecular C-H⋯O and N-H⋯O hydrogen bonds form two planar S(6) motifs. Inter-molecular O-H⋯O=C hydrogen bonds join mol-ecules into chains extending along the c axis.

2-Methylamino-5-nitrobenzoic acid

The title compound, C₈H₈N₂O₄, is almost planar (r.m.s. deviation = 0.037 Å) and an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds generate R₂²(8) loops. Inter­molecular N—H⋯O hydrogen bonds (involving the same H atom that forms the intra­molecular hydrogen bond) link the dimers into infinite sheets lying parallel to (102).

4-Hy-droxy-2-methyl-3,4-diphenyl-cyclo-pent-2-en-1-one

The asymmetric unit of title compound, C₁₈H₁₆O₂, contains two mol­ecules with slightly different conformations. In the first mol­ecule, the two phenyl rings make dihedral angles of 84.98 (11)° and the five-membered ring makes dihedral angles of 84.80 (12) and 73.00 (12)° with the phenyl rings; the corresponding angles for the second mol­ecule are 86.74 (11), 81.20 (13) and 71.36 (12)°. O—H⋯O hydrogen bonds between the hy­droxy and carbonyl groups are a feature of the crystal packing, which results in chains extending parallel to [100]. Weak C—H⋯O and C—H⋯π inter­actions are also observed.

Methyl 2-methyl-3,5-dinitro-benzoate

In the title compound, C(9)H(8)N(2)O(6), the methyl ester group is almost planar (r.m.s. deviation = 0.002 Å) and is oriented at a dihedral angle of 24.27 (16)° with respect to the benzene ring. The nitro groups make dihedral angles of 4.2 (5)° and 60.21 (11)° with the benzene ring. In the crystal, mol-ecules are linked by C-H⋯O inter-actions, resulting in zigzag chains.

Poly[(μ(5)-2-methyl-3,5-dinitro-benzoato)sodium]

In the crystal of the title coordination polymer, [Na(C(8)H(5)N(2)O(6))](n), the Na(I) ion is linked to five nearby anions. Their bonding modes are three monodentate carboxyl-ate O atoms, one O,O'-bidentate carboxyl-ate group and one O,O'-bidentate nitro group. This results in an irregular NaO(7) coordination geometry for the metal ion. This connectivity leads to a layered network propagating in (100).

2-Hydr-oxy-5-nitro-benzamide

In the title compound, C(7)H(6)N(2)O(4), an intra-molecular O-H⋯O hydrogen bond generates an S(6) ring. In the crystal, inversion dimers linked by pairs of N-H⋯O hydrogen bonds occur. Weak C-H⋯O links consolidate the packing, leading to R(2) (1)(7) and R(2) (2)(10) loops within (100) polymeric sheets.

rac-2-Iodo-3,4-dihydro-naphthalen-1(2H)-one

In the title compound, C(10)H(9)IO, the asymmetric unit contains two mol-ecules, in which the iodo-bearing six-membered rings adopt envelope conformations [displacements of the flap atoms = 0.419 (3) and 0.431 (3) Å]. In both mol-ecules, the I atoms are disordered over two set of sites in 0.54 (4):0.46 (4) and 0.71 (3):0.29 (3) ratios. In the crystal, the packing features a weak C-H⋯π inter-action.

2-Methyl-3,5-dinitro-benzoic acid

In the title compound, C₈H₆N₂O₆, the O atoms of the nitro groups, the methyl H atoms and the carboxyl C=O and C—OH groups are disordered over two sets of sites with an occupancy ratio of 0.595 (16):0.405 (16). In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds arise for both carboxyl disorder components and C—H⋯O bonds and weak C—H⋯π inter­actions consolidate the packing.

2-(1,3-Dioxoisoindolin-2-yl)propanoic acid

The crystal structure of the title compound, C₁₁H₉NO₄, consists of infinite one-dimensional polymeric chains due to inter­molecular O—H⋯O hydrogen bonds between the carboxyl­ate and carbonyl groups. The phthalimide ring system and the C—COO group are planar, with r.m.s. deviations of 0.0253 and 0.0067 Å, respectively, from their mean square planes and the dihedral angle between them is 66.41 (7)°. The mol­ecules are stabilized by C=O⋯π inter­actions and weak intra­molecular C—H⋯O hydrogen bonds.

(2R)-2-(1,3-Dioxoisoindolin-2-yl)-4-(methyl-sulfan-yl)butanoic acid

The title compound, C(13)H(13)NO(4)S, the 1,3-dioxoisoindolin-2-yl unit is planar (r.m.s. deviation 0.0192 Å) and is oriented at a dihedral angle of 79.14 (18)° to the carboxyl-ate group. An intra-molecular C-H⋯O hydrogen bond leads to the formation of a planar (r.m.s. deviation 0.0419 Å)R(5) ring motif. In the crystal, mol-ecules are connected through O-H⋯O and C-H⋯O hydrogen bonds with R(2) (2)(9) ring motifs into chains extending along the b axis.

2-Hydr-oxy-3-nitro-benzamide

The asymmetric unit of title compound, C₇H₆N₂O₄, contains two mol­ecules, one of which has a disordered nitro group with an occupancy ratio of 0.517 (9):0.483 (9) for the O atoms. Both mol­ecules contain an intra­molecular O—H⋯O hydrogen bond. In the crystal, both mol­ecules form inversion dimers linked by pairs of N—H⋯O hydrogen bonds, resulting in R₂²(8) ring motifs. The dimers are connected by further N—H⋯O links and weak C—H⋯O inter­actions, resulting in a layered motif.

2-Hydroxy-3-nitro-N-phenylbenzamide

The asymmetric unit of the title compound, C₁₃H₁₀N₂O₄, contains two crystallographically independent mol­ecules. The aromatic rings are oriented at dihedral angles of 24.39 (3) and 7.47 (3)° in the two mol­ecules and intra­molecular N—H⋯O and O—H⋯O hydrogen bonds result in the formation of two planar six-membered rings. In the crystal structure, inter­molecular O—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into chains, forming R₂²(10) ring motifs. Weak π–π contacts between the benzene and phenyl rings [centroid–centroid distance = 3.955 (3) Å] may further stabilize the structure.

Octa-methyldi-μ(3)-oxido-bis-(μ(2)-thio-phene-3-acetato-κO:O')(thio-phene-3-acetato-κO)tetra-tin(IV)

In the centrosymmetric title compound, [Sn₄(CH₃)₈(C₆H₅O₂S)₄O₂], the central four-membered planar ring (Sn₂O₂) makes dihedral angles of 66.28 (12) and 77.43 (11)° with the heterocyclic rings of the bridging and monodentate ligands, respectively. One Sn^IV atom adopts a distorted SnO₃C₂ trigonal-bipyramidal geometry, with both C atoms in equatorial sites and the other a grossly distorted SnO₄C₂ octa­hedral or irregular arrangement. In the crystal, the mol­ecules are connected into pillar-like polymeric units making R₂²(12) ring motifs due to inter­molecular C—H⋯O inter­actions. C–H⋯π inter­actions are also present. The O atoms of the chelating ligands and the S atom of the monodentate ligand are disordered over two sets of sites in a 0.65 (6):0.35 (6) ratio

Diastereotopy in some 3,4-dihydroisocoumarins--effect of changing the substituents on the chiral centre

Diastereotopy has been investigated in eight different derivatives of 3,4-dihydroisocoumarins by changing the substituent on the pyran ring chiral centre, C-3. A diastereotopic NMR effect is observed for the prochiral methylene protons on the benzopyran ring and the effect is greatly influenced by the pi-electron system of the substituent. The effect is also observed for the substituents, however, the extent of diastereotopy depends upon their nature and the separation of methylene groups from the chiral centre.