Synthesis, crystal structure and in-silico evaluation of arylsulfonamide Schiff bases for potential activity against colon cancer.

This report presents a comprehensive investigation into the synthesis and characterization of Schiff base compounds derived from benzenesulfonamide. The synthesis process, involved the reaction between N-cycloamino-2-sulfanilamide and various substituted o-salicylaldehydes, resulted in a set of compounds that were subjected to rigorous characterization using advanced spectral techniques, including 1H NMR, 13C NMR and FT-IR spectroscopy, and single-crystal X-ray diffraction. Furthermore, an in-depth assessment of the synthesized compounds was conducted through Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) analysis, in conjunction with docking studies, to elucidate their pharmacokinetic profiles and potential. Impressively, the ADMET analysis showcased encouraging drug-likeness properties of the newly synthesized Schiff bases. These computational findings were substantiated by molecular properties derived from density functional theory (DFT) calculations using the B3LYP/6-31G* method within the Jaguar Module of Schrödinger 2023-2 from Maestro (Schrodinger LLC, New York, USA). The exploration of frontier molecular orbitals (HOMO and LUMO) enabled the computation of global reactivity descriptors (GRDs), encompassing charge separation (Egap) and global softness (S). Notably, within this analysis, one Schiff base, namely, 4-bromo-2-{N-[2-(pyrrolidine-1-sulfonyl)phenyl]carboximidoyl}phenol, 20, emerged with the smallest charge separation (ΔEgap = 3.5780 eV), signifying heightened potential for biological properties. Conversely, 4-bromo-2-{N-[2-(piperidine-1-sulfonyl)phenyl]carboximidoyl}phenol, 17, exhibited the largest charge separation (ΔEgap = 4.9242 eV), implying a relatively lower propensity for biological activity. Moreover, the synthesized Schiff bases displayed remarkeable inhibition of tankyrase poly(ADP-ribose) polymerase enzymes, integral in colon cancer, surpassing the efficacy of a standard drug used for the same purpose. Additionally, their bioavailability scores aligned closely with established medications such as trifluridine and 5-fluorouracil. The exploration of molecular electrostatic potential through colour mapping delved into the electronic behaviour and reactivity tendencies intrinsic to this diverse range of molecules.

rac-Hy-droxy-isovaleric acid.

The title compound (systematic name: rac-2-hydroxy-3-methylbutanoic acid), C5H10O3, is the constitutional isomer of α-hy-droxy-butanoic acid. In the crystal, hydrogen bonds involving the alcoholic hydroxyl group give rise to centrosymmetric dimers that are extended to sheets perpendicular to the crystallographic c axis.

Copper(II)-photocatalyzed Hydrocarboxylation of Schiff bases with CO2: antimicrobial evaluation and in silico studies of Schiff bases and unnatural α-amino acids.

We synthesized and characterized two copper(II) complexes: [CuL2Cl]Cl and [CuL'2Cl]Cl, where L = 2,2'-bipyridine and L' = 4,4'-dimethyl-2,2'-bipyridine. We evaluated their photocatalytic hydrocarboxylation properties on a series of synthesized Schiff bases (SBs): (E)-1-(4-((5-bromo-2-hydroxybenzylidene)amino)phenyl)ethanone (SB1), (E)-N-(4-(dimethylamino)benzylidene)benzo[d]thiazol-2-amine (SB2), (E)-4-Bromo-2-((thiazol-2-ylimino)methyl)phenol (SB3), and (E)-4-((5-bromo-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (SB4). Under mild photocatalytic reaction conditions (room temperature, 1 atm CO2, 30-watt Blue LED light), the derivatives of α-amino acids UAA1-4 were obtained with yields ranging from 5% to 44%. Experimental results demonstrated that [CuL2Cl]Cl exhibited superior photocatalytic efficiency compared to [CuL'2Cl]Cl, attributed to favourable electronic properties. In silico studies revealed strong binding strengths with E. faecalis DHFR (4M7U) for docked Schiff bases (SB) and unnatural α-amino acids (UAAs). In vitro studies further demonstrated significant antimicrobial and antifungal activity for SB2, SB3, and SB4, while none of the synthesized UAAs exhibited such properties, primarily due to the electronic and binding properties of these molecules.Communicated by Ramaswamy H. Sarma.

[1,1'-Bi-cyclo-hexa-ne]-1,1'-diol.

The title compound, C12H22O2, is a symmetric diol derived from the pinacol coupling of cyclo-hexa-none. The asymmetric unit contains three complete mol-ecules. The cyclo-hexane moieties adopt chair conformations. Cooperative hydrogen bonding connects the individual mol-ecules to infinite chains propagating along the crystallographic a-axis direction.

N-Cycloamino substituent effects on the packing architecture of ortho-sulfanilamide molecular crystals and their in silico carbonic anhydrase II and IX inhibitory activities.

In the search for new `sulfa drugs' with therapeutic properties, o-nitrosulfonamides and N-cycloamino-o-sulfanilamides were synthesized and characterized using techniques including 1H NMR, 13C NMR and FT-IR spectroscopy, and single-crystal X-ray diffraction (SC-XRD). The calculated density functional theory (DFT)-optimized geometry of the molecules showed similar conformations to those obtained by SC-XRD. Molecular docking of N-piperidinyl-o-sulfanilamide and N-indolinyl-o-sulfanilamide supports the notion that o-sulfanilamides are able to bind to human carbonic anhydrase II and IX inhibitors (hCA II and IX; PDB entries 4iwz and 5fl4). Hirshfeld surface analyses and DFT studies of three o-nitrosulfonamides {1-[(2-nitrophenyl)sulfonyl]pyrrolidine, C10H12N2O4S, 1, 1-[(2-nitrophenyl)sulfonyl]piperidine, C11H14N2O4S, 2, and 1-[(2-nitrophenyl)sulfonyl]-2,3-dihydro-1H-indole, C14H12N2O4S, 3} and three N-cycloamino-o-sulfanilamides [2-(pyrrolidine-1-sulfonyl)aniline, C10H14N2O2S, 4, 2-(piperidine-1-sulfonyl)aniline, C11H16N2O2S, 5, and 2-(2,3-dihydro-1H-indole-1-sulfonyl)aniline, C14H14N2O2S, 6] suggested that forces such as hydrogen bonding and π-π interactions hold molecules together and further showed that charge transfer could promote bioactivity and the ability to form biological interactions at the piperidinyl and phenyl moieties.

Zinc(II) Complex Containing Oxazole Ring: Synthesis, Crystal Structure, Characterization, DFT Calculations, and Hirshfeld Surface Analysis.

A new complex of Zn(II), with 5-chloro-2-methylbenzoxazole ligand (L), has been synthesized by the reaction of zinc dichloride with the ligand (L= C8H6ClNO) in ethanol solution: dichloridobis(5-chloro-2-methyl-1,3-benzoxazole)-zinc(II), C16H12Cl4N2O2Zn. The synthesized complex has been fully characterized by elemental analysis, molar conductivity, FT­IR, UV­Vis, and single-crystal X-ray diffraction (XRD).  The XRD analysis reveals that the complex has a 1:2 metal-to-ligand ratio. The zinc(II) complex has a distorted tetrahedral geometry with two coordinated nitrogen atoms from the ligand. Density Functional Theory (DFT) calculations were performed at the B3LYP level of theory using the LANL2DZ basis set for metal complex and the 6-31G(d) basis set for non-metal elements to determine the optimum geometry structure of the complex, and the calculated HOMO and LUMO orbital energies were presented. A natural bond orbital (NBO) analysis was carried out on the molecules to analyze the atomic charge distribution before and after the complexation of the ligand.  The Hirshfeld surface mapped over dnorm, shape index, and curvature exhibited strong H...Cl/Cl...H and H...H intermolecular interactions as the principal contributors to crystal packing.

Cu(II)-Catalysed Hydrocarboxylation of Imines Utilizing CO2 to Synthesize α-Unsaturated Aminocarboxylic Acids.

Here, we report the Cu(II)-photocatalysed hydrocarboxylation of imines (C=N) from a series of synthesized Schiff Base derivatives, namely (E)-1-(4-((4-methylbenzylidene)amino)phenyl)ethanone, (E)-1-(3-((5-bromo-2-hydroxybenzylidene)amino)phenyl)ethanone, (E)-4-((5-bromo-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, and (E)-1,5-dimethyl-4-((4-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-one, with carbon dioxide (CO2) to generate disubstituted amino acids. Under mild conditions (atmospheric pressure of CO2, room temperature, and 30 W Blue LED light), good to excellent yields confirming the formation of substituted amino acid unsaturated acid derivatives were obtained. Single crystal X-ray diffraction (SC-XRD) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) confirmed the square pyramidal geometry of the Cu(II) photocatalyst. Docking and DFT calculations of the substituted amino acid unsaturated acid derivatives showed their potential as antimicrobial molecules.

Reaction of Perrhenate with Phthalocyanine Derivatives in the Presence of Reducing Agents and Rhenium Oxide Nanoparticles in Biomedical Applications.

A novel alternative route to access rhenium(V)-phthalocyanine complexes through direct metalation of metal-free phthalocyanines (H2 Pcs) with a rhenium(VII) salt in the presence of various two-electron reducing agents is presented. Direct ion metalation of tetraamino- or tetranitrophthalocyanine with perrhenate (ReO4- ) in the presence of triphenylphosphine led to oxidative decomposition of the H2 Pcs, giving their respective phthalonitriles. Conversely, treatment of H2 Pcs with ReO4- employing sodium metabisulfite yielded the desired ReV O-Pc complex. Finally, reaction of H2 Pcs with ReO4- and NaBH4 as reducing agent led to the formation of rhenium oxide (Rex Oy ) nanoparticles (NPs). The NP synthesis was optimised, and the Rex Oy NPs were capped with folic acid (FA) conjugated with tetraaminophthalocyanine (TAPc) to enhance their cancer cell targeting ability. The cytotoxicity profile of the resultant Rex Oy -TAPc-FA NPs was assessed and found to be greater than 80 % viability in four cell lines, namely, MDA-MB-231, HCC7, HCC1806 and HEK293T. Non-cytotoxic concentrations were determined and employed in cancer cell localization studies. The particle size effect on localization of NPs was also investigated using confocal fluorescence and transmission electron microscopy. The smaller NPs (≈10 nm) were found to exhibit stronger fluorescence properties than the ≈50 nm NPs and exhibited better cell localization ability than the ≈50 nm NPs.

Synthesis, crystal structure and docking studies of tetracyclic 10-iodo-1,2-dihydroisoquinolino[2,1-b][1,2,4]benzothiadiazine 12,12-dioxide and its precursors.

The title compound, 10-iodo-1,2-dihydroisoquinolino[2,1-b][1,2,4]benzothiadiazine 12,12-dioxide, C15H11IN2O2S (8), was synthesized via the metal-free intramolecular N-iodosuccinimide (NIS)-mediated radical oxidative sp3-C-H aminative cyclization of 2-(2'-aminobenzenesulfonyl)-1,3,4-trihydroisoquinoline, C15H16N2O2S (7). The amino adduct 7 was prepared via a two-step reaction, starting from the condensation of 2-nitrobenzenesulfonyl chloride (4) with 1,2,3,4-tetrahydroisoquinoline (5), to afford 2-(2'-nitrobenzenesulfonyl)-1,3,4-trihydroisoquinoline, C15H14N2O4S (6), in 82% yield. The catalytic hydrogenation of 6 with hydrogen gas, in the presence of 10% palladium-on-charcoal catalyst, furnished 7. Products 6-8 were characterized by their melting points, IR and NMR (1H and 13C) spectroscopy, and single-crystal X-ray diffraction. The three compounds crystallized in the monoclinic space group, with 7 exhibiting classical intramolecular hydrogen bonds of 2.16 and 2.26 Å. All three crystal structures exhibit centrosymmetric pairs of intermolecular C-H...π(ring) and/or π-π stacking interactions. The docking studies of molecules 6, 7 and 8 with deoxyribonucleic acid (PDB id: 1ZEW) revealed minor-groove binding behaviours without intercalation, with 7 presenting the most favourable global energy of the three molecules. Nonetheless, molecule 8 interacted strongly with the DNA macromolecule, with an attractive van der Waals energy of -15.53 kcal mol-1.

Exploring intermolecular contacts in multi-substituted benzaldehyde derivatives: X-ray, Hirshfeld surface and lattice energy analyses.

Crystal structures of six benzaldehyde derivatives (1-6) have been determined and their supramolecular networks were established by an X-ray crystallographic study. The study has shown that the compounds are linked by various intermolecular interactions such as weak C-H⋯O hydrogen bonding, and C-H⋯π, π-π and halogen bonding interactions which consolidate and strengthen the formation of these molecular assemblies. The carbonyl group generates diverse synthons in 1-6via intermolecular C-H⋯O hydrogen bonds. An interplay of C-H⋯O hydrogen bonds, and C-H⋯π and π-π stacking interactions facilitates the formation of multi-dimensional supramolecular networks. Crystal packings in 4 and 5 are further generated by type I halogen⋯halogen bonding interactions. The differences in crystal packing are represented by variation of substitution positions in the compounds. Structure 3 is isomorphous with 4 but there are subtle differences in their crystal packing. The nature of intermolecular contacts in the structures has been studied through the Hirshfeld surfaces and two-dimensional fingerprint plots which serve as a comparison in constructing different supramolecular networks. The intermolecular interaction energies are quantified utilizing theorectical calculations for the title compounds and various analogous structures retrieved from the Cambridge Structural Database (CSD). Also intermolecular interactions for the molecular pairs are exctrated from respective crystal structures. Essentially, there are some invariant and variable intermolecular contacts realized between different groups in all six structures. The ab initio DFT total lattice energy (E Tot) calculations showed a direct correlation with thermal strengths of the title compounds.

Synthesis, Characterization and Biological Activity of Some Dithiourea Derivatives.

Novel dithiourea derivatives have been designed as HIV-1 protease inhibitors using Autodock 4.2, synthesized and characterized by spectroscopic methods and microanalysis. 1-(3-Bromobenzoyl)-3-[2-([(3-bromophenyl)formami-do]methanethioylamino)phenyl]thiourea (10) and 3-benzoyl-1[(phenylformamido)methanethioyl]aminothiourea (12) gave a percentage viability of 17.9 ± 5.6% and 11.2 ± 0.9% against Trypanosoma brucei. Single crystal X-ray dif-fraction analysis of 1-benzoyl-3-(5-methyl-2-[(phenylformamido)methanethioyl]aminophenyl)thiourea (1), 3-ben-zoyl-1-(2-[(phenylformamido)methanethioyl]aminoethyl)thiourea (11), 3-benzoyl-1-[(phenylformamido)methan-ethioyl]aminothiourea (12) and 3-benzoyl-1-(4-[(phenylformamido)methanethioyl]aminobutyl)thiourea (14) have been presented. 1-(3-Bromobenzoyl)-3-[2-([(3-bromophenyl)formamido]methanethioylamino)phenyl]thiourea (10) gave a percentage inhibition of 97.03 ± 0.37% against HIV-1 protease enzyme at a concentration of 100 ?M.

New VIVO-complexes for oxidative desulfurization of refractory sulfur compounds in fuel: synthesis, structure, reactivity trend and mechanistic studies.

A series of 5-coordinate oxidovanadium(iv) complexes based on 2-(2'-hydroxyphenyl)imidazole (HPIMH), with substituent groups of different electronegativities on the phenolic para position (HPIMX; X = -H, -Br, -OMe and -NO2), were synthesized and characterized. Three of these complexes were characterized by single crystal X-ray diffraction, [VIVO(PIMH)2], [VIVO(PIMBr)2] and [VIVO(PIMNO2)2], as well as a dioxidovanadium(v) compound ([VVO2(PIMH)(PIMH2)]). The complexes were tested for their catalytic activities in the oxidation of dibenzothiophene (DBT), the major refractory organosulfur compound found in fuel. The nitro substituted compound [VIVO(PIMNO2)2] had the highest catalytic oxidation activity followed by: [VIVO(PIMH)2] > [VIVO(PIMBr)2] > [VIVO(PIMMeO)2]. The decrease in activity is attributed to the different electronegativities of the substituent groups, which influence the electron density on the metal center, the V[double bond, length as m-dash]O bond distances and infrared stretching bands. Geometry index (τ) values calculated from single crystal X-ray diffraction (SC-XRD) data and DFT studies provided further insights on the trend in activity observed. SC-XRD, EPR, 51V NMR and UV-Vis spectroscopies, and DFT studies were instrumental in studying the mechanism of the catalyzed reaction and proposal of intermediate species. Both radical and non-radical pathways are plausible for the catalytic oxidation and participation of reactive oxygen species in both pathways is also postulated.

Synthesis and anti-inflammatory activity of diversified heterocyclic systems.

In continuation with our research program on the development of novel bioactive molecules, we report herein the design and synthesis of a series of diversified heterocycles (4-22). The synthesized compounds were evaluated for their anti-inflammatory activity. The chemical structures of the newly synthesized compounds have been confirmed by NMR, FTIR, and microanalysis.

Bis(µ-N,N-di-allyl-dithio-carbamato)bis[(N,N-di-allyl-dithio-carbamato)cadmium].

The title compound, [Cd2(C7H10NS2)4], is a neutral dinuclear cadmium(II) complex bearing four bis N,N-di-allyl-di-thio-carbamate ligands coordinating to two CdII cations. In each of the monomeric subunits, there are four S atoms of two di-thio-carbamate ligands [Cd-S = 2.5558 (3), 2.8016 (3), 2.6050 (3) and 2.5709 (3) Å] that coordinate to one CdII atom in a bidentate mode. The dimers are located over an inversion centre bridged by two additional bridging Cd-S bonds [2.6021 (3) Å], leading to a substantial distortion of the geometry of the monomeric subunit from the expected square-planar geometry. The five-coordinate environment around each of the CdII ions in the dimer is best described as substanti-ally tetra-gonally distorted square pyramidal. The di-thio-carbamate groups are themselves planar and are also coplanar with the CdII ions. The negative charge on these groups is delocalized by resonance across the S atoms bound to the CdII cation. This delocalization of the π electrons in the di-thio-carbamate groups also extends to the C-N bonds as they reveal significant double bond character [C-N = 1.3213 (16) and 1.3333 (15) Å].

Crystal structure of (6E,20E)-3,24-di-fluoro-13,14,28,29-tetra-hydro-5H,22H-tetra-benzo[e,j,p,u][1,4,12,15]tetra-oxa-cyclo-docosine-5,22-dione.

The conformation of the title compound, C34H26F2O6, is cone-shaped, partially determined by intra-molecular C-H⋯O short contacts. The benzene rings at the top of the cone are inclined to one another by 73.10 (7)°, while the benzene rings at the bottom of the cone are inclined to one another by 35.49 (8)°. In the crystal, mol-ecules are linked by C-H⋯O and C-H⋯F hydrogen bonds, forming a three-dimensional supra-molecular structure. There are also C-H⋯π contacts present within the framework structure.

Metal Complexes of New Bioactive Pyrazolone Phenylhydrazones; Crystal Structure of 4-Acetyl-3-methyl-1-phenyl-2-pyrazoline-5-one phenylhydrazone Ampp-Ph.

The condensation reaction of phenylhydrazine and dinitrophenylhydrazine with 4-acetyl and 4-benzoyl pyrazolone precipitated air-stable acetyldinitrophenylhydrazone Ampp-Dh, benzoylphenylhydrazone Bmpp-Ph and benzoyldinitrophenylhydrazone Bmpp-Dh in their keto imine form; a study inspired by the burning interest for the development of new bioactive materials with novel properties that may become alternative therapeutic agents. Elemental analysis, FTIR, ¹H, and (13)C NMR, and mass spectroscopy have been used to justify their proposed chemical structures, which were in agreement with the single crystal structure of Bmpp-Dh earlier reported according to X-ray crystallography. The single crystal structure of 4-acetyl-3-methyl-1-phenyl--pyrazoline-5-one phenylhydrazone Ampp-Ph, which crystallizes in a triclinic crystal system with a P-1 (No. 2) space group is presented. Octahedral Mn(II), Ni(II), Co(II), and Cu(II) complexes of these respective ligands with two molecules each of the bidentate Schiff base, coordinating to the metal ion through the azomethine nitrogen C=N and the keto oxygen C=O, which were afforded by the reaction of aqueous solutions of the corresponding metal salts with the ligands are also reported. Their identity and proposed structures were according to elemental analysis, FTIR spectroscopy, UV-VIS spectrophotometry (electronic spectra) and Bohr magnetic moments, as well as thermogravimetric analysis (TGA) results. A look at the antibacterial and antioxidant activities of synthesized compounds using the methods of the disc diffusion against some selected bacterial isolates and 1,1-diphenyl-2-picryl-hydrazil (DPPH) respectively, showed biological activities in relation to employed standard medicinal drugs.

Benzimidazole or Diamide From a Reaction of Diamines and Carboxylic Acids or Acid Chlorides: Crystal Structures and Theoretical Studies.

A reaction of an acid chloride with a diamine yielded a diamide. m-Toluic acid was chlorinated to m-toluoyl chloride and subsequently reacted with 4-methyl-o-phenylenediamine in pyridine to obtain 3-methyl-N-[2-(3-methylbenzamido)phenylbenzamide (I). 2-(3-Methylphenyl)-1H-benzimidazole (II) has been obtained upon reacting o-phenylenediamine with m-toluic acid in polyphosphoric acid and toluene. The compounds have been characterized by IR, NMR, microanalyses and GC-MS. The crystal structures of the compounds have been discussed. DFT calculations of the frontier orbitals of the precursor compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity in the formation of the diamides and benzimidazoles. The synthesis of the amide from a diamine was seen to be favoured in the presence of a good leaving group attached to the carbonyl as in the case of acid chloride. However, the synthesis of benzimidazoles was found to be favoured in the presence of an excess of a protonating agent and high temperature.

Synthesis and Characterization of Bioactive Acylpyrazolone Sulfanilamides and Their Transition Metal Complexes: Single Crystal Structure of 4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one Sulfanilamide.

Two Schiff base ligands Ampp-Sn 1 and Bmpp-Sn 2, afforded by a condensation reaction between sulfanilamide and the respective acylpyrazolone carbonyl precursors, their Mn(II), Co(II), Ni(II), and Cu(II) complexes prepared by the reaction of ligands and corresponding metal salts in aqueous solutions, were synthesized and then characterized by both analytical and spectroscopic methods, in a view to developing new improved bioactive materials with novel properties. On the basis of elemental analysis, spectroscopic and TGA results, transition metal complexes, with octahedral geometry having two molecules of the bidentate keto-imine ligand each, have been proposed. The single crystal structure of Bmpp-Sn according to X-ray crystallography showed a keto-imine tautomer type of Schiff base, having three intramolecular bonds, one short N2⋯H2⋯O3 hydrogen bond of 1.90 Å and two long C13⋯H13⋯O2 and C32⋯H32⋯O3 hydrogen bonds of 2.48 Å. A moderate to low biological activities have been exhibited by synthesized compounds when compared with standard antimicrobial agents on screening the synthesized compounds against Staphylococcus aureus, Bacillus pumilus, Proteus vulgaris, and Aeromonas hydrophila for antibacterial activity and against free radical 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) for antioxidant activity.

Clathrates of TETROL: Further Aspects of the Selective Inclusion of Methylcyclohexanones in Their Energetically Unfavorable Axial Methyl Conformations.

(+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) functions as a highly efficient host for the inclusion of cyclohexanone and 2-, 3-, and 4-methylcyclohexanone, all with 1:1 host/guest ratios. Most extraordinarily, the 3- and 4-methyl isomers are uniquely included in their higher energy axial methyl conformations rather than as their more energetically favorable equatorial analogues. In contrast, 2-methylcyclohexanone is included more conventionally in the equatorial methyl conformation. During recrystallization of TETROL from racemic 2- and 3-methylcyclohexanone, some preference is shown by the host for the (R)-enantiomer. In the latter case, this is attributed to a much stronger H-bond between a hydroxyl group of TETROL and the carbonyl group of the (R)-enantiomer (O···O 2.621(2) Å) compared with a significantly weaker H-bond to the (S)-enantiomer (3.125(8) Å). In the former instance, hydrogen-bond strengths to both enantiomers are similar, but the (R)-enantiomer engages in three (guest)CH···π(host) and three (guest)H···Car(host) contacts, whereas fewer interactions of these types are observed for the (S)-enantiomer. Calculations of geometries of the guest cyclohexanones were determined at the MP2/6-311++G(2df,2p) level and compared with those obtained at the G3(MP2) level. Finally, an interesting correlation between crystal packing indices for the three methylcyclohexanone clathrates and their respective desolvation onset temperatures was identified.

Ethyl (4-benzyloxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate and a redetermination of ethyl (4RS)-4-(4-methoxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate, as its 0.105-hydrate, both at 200†K: subtly different hydrogen-bonded ribbons.

Two sulfanylidene-1,2,3,4-tetrahydropyrimidine derivatives have been synthesized using acid-catalysed cyclocondensation reactions between thiourea, ethyl 3-oxobutanoate and substituted benzaldehydes. In each of ethyl (4RS)-4-(4-benzyloxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate, C21H22N2O3S, (I), where Z' = 2, and ethyl (4RS)-4-(4-methoxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate 0.105-hydrate, C15H18N2O3S·0.105H2O, (II), the reduced pyrimidine ring adopts a conformation intermediate between the boat, screw-boat and twist-boat forms. In (I) and (II), a combination of N-H...O and N-H...S hydrogen bonds links the organic molecules into ribbons containing alternating R2(2)(8) and R4(4)(20) rings. In (I), the ribbon contains three types of ring, viz. two different R2(2)(8) rings which are both centrosymmetric and R4(4)(20) rings which are not centrosymmetric. In (II), the ribbon contains two types of ring, both of which are centrosymmetric. In compound (II), the ribbons enclose continuous channels which run along the twofold rotation axes in the space group C2/c, and the partial-occupancy water molecules lie within these channels. Structural comparisons are made with a number of related compounds.