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molecules are omitted for clarity: S10-C9 1.739(4); S8-C9 1.752(5); S8-C7 1.752(4); N6-C7 1.346(5); N6-N24 1.383(5);N6-C5 1.461(5); N24-C9 1.286(6); C7-N26 1.310(5); O28-C27 1.248(5); N26-C27 1.372(5); C7-S8-C9 88.1(2); C9-N24-N6 109.3(3); C7-N6-N24 117.9(3); N6-C7-S8 108.6(3). (b) ORTEP diagram show-ing the relationship of rings and subunits (Ct1-Ct2 4.788 A; Ct3-Ct44.247 A, Ct refers to the centroid of ring). There is a pseudo-mirror plane passing through the middle of molecule.

which we performed preliminary trial shown in experimentals. To form the macrocyclic compound, two of these hetero-cyclic rings were linked by either ether chains or alkyl chains as shown in Scheme 1. The crystal structures of many of these compounds were determined by interpreting X-ray diffraction patterns. The 15-, 18-, 21-, 22-, 23-, and 25-membered macro-cyclic compounds shown in Scheme 1 produce central cavities of different sizes and shapes. The synthetic procedures are similar to those previously reported for macrocycles composed of two 5-mercapto-3

In the presence of ammonia, methyl N-(bromoacetyl)anthranilate (4) is cyclized into 3H-1,4-benzodiaze-pine-2,5(1H,4H)-dione (1). However, when 4 is replaced with methyl N-(chloroacetyl)anthranilate (6), the only heterocyclic product formed in the reaction is 2-(chloromethyl)quinazoline-4(3H)-one (7). Under analogous conditions, 3-haloacetamidocrotonates (9, 10) do not yield any heterocyclic products and no 1,4-diazepines can be obtained.

The aim of the study was to investigate the mechanical properties and biodegradability of poly(trimethylenecarbonate-e-caprolactone)-block-poly(p-dioxanone) [P(TMC-e-CL)-block-PDO] in comparison with poly(p-dioxanone) and poly(glycolide-e-caprolactone) (Monocryl®) monofilaments in vivo and in vitro. P(TMC-e-CL)-block-PDO copolymer and poly(p-dioxanone) were prepared by using ring-opening polymerization reaction. The monofilament fibers were obtained using conventional melt spun methods. The physicochemical and mechanical properties, such as viscosity, molecular weight, crystallinity, and knot security, were studied. Tensile strength, breaking strength retention, and surface morphology of P(TMC-e-CL)-block-PDO, poly(p-dioxanone), and Monocryl monofilament fibers were studied by immersion in phosphate-buffered distilled water (pH 7.2) at 37°C and in vivo. The implantation studies of absorbable suture strands were performed in gluteal muscle of rats. The polymers, P(TMC-e-CL)-block-PDO, poly(p-dioxanone), and Monocryl, were semicrystalline and showed 27, 32, and 34% crystallinity, respectively. Those mechanical properties of P(TMC-e-CL)-block-PDO were comparatively lower than other polymers. The biodegradability of poly(dioxanone) homopolymer is much slower compared with that of two copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 737–743, 2006

A series of 4-substituted (benzo[b]thiophene-2-carbonyl)guanidines was synthesized and evaluated for the NHE-1 inhibitory activity and cardioprotective efficacy both in vitro and in vivo. Several analogs exhibited a strong inhibition on NHE-1, and which was generally well correlated with their cardioprotective efficacy. Especially the 4-nitro 20 and cyano 50 compounds excellently improved the cardiac function and reduced infarct size against ischemia/reperfusion injury.

A series of poly(trimethylenecarbonate-e-caprolactone)-block-poly(p-dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(e-caprolactone) random copolymer was synthesized with stannous-2-ethylhexanoate and followed by adding p-dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by 1H and 13C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790–2799, 2005

Amide linkages are present in key natural products and in many biologically active molecules. Therefore, the formation of amide bonds is important to both synthetic chemists and biologists. Approximately 66% of all preliminary screening reactions in industrial medicinal chemistry laboratories involve amide formation. Although many methods have been developed for amide synthesis, a procedure for the direct coupling of amines with an acid in the presence of coupling agents without prior activation would be useful for building small-molecule libraries and for key steps in total syntheses. Condensing agents such as carbodiimides or other activating agents are generally employed under dry conditions. However, the condensing agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4methylmorpholium chloride (DMT-MM) can be used to prepare carboxamides in alcohol or water. This reaction is technically simple and relatively easy to implement, requiring only a mixing of acids, amines, and DMTMM in MeOH or H2O. The synthesis of DMT-MM is also relatively simple, and it can be prepared from CDMT (2chloro-4,6 dimethoxy-1,3,5-triazine) and N-metheylmorphorine (NMM) in THF. The current report describes the application of microwave-induced acceleration to further improve the reaction conditions for amide synthesis using DMT-MM. Highspeed synthesis using microwave technology has attracted considerable attention in organic chemistry. Microwave irradiation provides advantages over conventional heating for chemical transformations, including accelerated reaction rates (and consequently reduced reaction times), higher yields, and cleaner reactions. These advantages led us to evaluate the use of microwave irradiation for amidation reactions involving less reactive secondary and primary amines with acid in the presence of DMT-MM. We also compared the effectiveness of dicyclohexylcarbodiimide (DCC), a well-known condensing reagent, when coupled with microwave irradiation versus classical thermal methods. The reactions were performed by dissolving amines, carboxylic acids, and the condensing agent in solvent, followed by irradiation in a temperature-controlled microwave oven. For comparison, the same reactions were carried out under conventional heating conditions. The amidation of 2-phenylethylamine (a primary amine) with substituted benzoic acid in the presence of DMT-MM in MeOH gave a yield of over 90% products within 25 min at 110 C with microwave irradiation. The reaction time with conventional heating was seven times that with microwave irradiation, and the yield was less than 10-20% of the yield with the microwave-assisted method. The reaction of piperidine (a secondary amine) with benzoic acid afforded a 91% yield within 30 min at 150 C with microwave irradiation; note the higher reaction temperature and longer reaction time compared with those of the primary amine reaction. Amidation of piperidine with substituted benzoic acid in the presence of DCC with pyridine in THF yielded more than 60% products within 25 min at 120 C with microwave irradiation. Thus, DMT-MM was a much more effective coupling agent than DCC. Further increases in reaction temperature were limited by the potential of solvents for producing an explosive atmosphere within the micro

moieties and a 1,3-benzenedimethanethiol subunit, this study describes the synthesis of a metalloreceptor boasting a cavity size amenable to molecular recognition of DNA/RNA nucleo-bases, including cytosine, adenine, and thymine as well as imidazole, pyrazine, and 2,6-dimethylpyrazine. Both the synthesis and characteristics of molecular recognition were as described in previous reports.

5-Amino-2,3-dihydro-1,2,4-oxadiazol-3-one 2 was synthesized as an analogue of cytosine. Among the possible four tautomers it was established by spectroscopic methods and ab initio calculations that it exists as a lactam form 2b like cytosine. The NH is more acidic than NH2, thus it could be regioselectively mesylated and acetylated under basic conditions.

5-Amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 can be synthesized from 5-amino-2H-1,2,4-thiadiazolin-3-one (1–1) via a selective acylation with an acid anhydride in pyridine. The 1H nmr spectral characteristics of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 is in particular, compared with 5-amino-2H-1,2,4-thiadiazolin-3-one (1–1) and 5-amino-2-alkyl-1,2,4-thiadiazolin-3-ones 1–2, 1–3. The 5-amino group of 2–1 appeared as two peaks in its 1H nmr spectrum, which merged to a single peak at a higher temperature, while those of compound 1–1, 1–2 and 1–3 appear only as a single peak. The restricted rotation of the C(5)-N(5) (at amino) bond of 5-amino-2-acetyl-1,2,4-thiadiazolin-3-one (2a-1) is about 14.5 Kcal/mol.

Fragment pathways of 3-alkyl and acyl-5-amino-1,3,4-thiadiazolin-2-ones were completely assigned by mass analyzed kinetic energy spectra (MIKE), collisional activated dissociation (CAD) spectra and high resolution mass spectra. [NH2CS]+ and [S[dbnd]C[dbnd]O]+ ions were directly formed from molecular ion of the 3-alkyl compounds and from 5-amino-3H−1,3,4 -thiadiazolin-2-one ion ( 1 ) which was produced by McLafferty rearrangement from molecular ion of 3-acyl compounds. A loss of neutral SCO was only detected from 3-alkyl substituted molecular ions.

Selective transport of alkaline-earth cations in a bulk liquid membrane system by lipophilic acyclic polyether dicarboxylic acids is reported. Introduction of proton-ionizable groups into such polyethers shows a distinct advantage over neutral macrocycles in that transfer of a metal ion into an organic medium does not require concomitant transport of an aqueous phase anion. A new organic ligand 1,5-bis[2-(2′-carboxypentadecyloxy)phenoxy]-3-oxapentane ( 8 ) which bears a tetradecyl group as an alkyl chain at the α-position of the carboxylic acid side-arm unit is sufficiently lipophilic to avoid loss of the complexing agent into the aqueous phase during solvent extraction and exhibited a calcium selectivity over other alkaline-earth cations.

by providing sites for functionalizationnot only on the aromatic rings but also on the bridging sulfuratoms. Thiacalixarenes possess additional coordination sitesand the cavity dimensions are increased compared withanalogous calixarenes. Unlike calix[4]arenes, thiacalix[4]-arenes show affinity for transition metal ions because thesulfur atoms in the calixarene framework take part in themetal ion complexation.

The asymmetric unit of the title compound, C2H3N3OS, contains three independent molecules which are essentially planar, with r.m.s. deviations of 0.011 (2)–0.027 (2) Å from the mean plane defined by the seven non-H atoms. In the crystal, N—H...N and N—H...O hydrogen bonds link the molecules into a sheet parallel to the (111) plane.

In the title compound, C11H13NO3S, the dihedral angle between the benzyl and carbamate groups is 12.67 (10)°. The S atom and the carbonyl O atom are positioned anti to each other. In the crystal, pairs of N—H...S hydrogen bonds link molecules into inversion dimers.

5-Aroylamino-3H-1,3,4-thiadiazole-2-thiones 2 have been synthesized by acylation of 5-amino-3H-1,3,4-thiadiazole-2-thione 1. 5-Aroylamino-3H-1,3,4-thiadiazole-2-thiones can exist in two tautomeric forms — a thiol form and a thione form. On the basis of the 13C nmr spectra and additional experimental information, it has been established that the thione form is the stable form in which these compounds exist.

In situ oxidation of cyclohexane to cyclohexanol and cyclohexanone was investigated with hydrogen peroxide produced from hydrogen and oxygen at a temperature of 30 °C and under atmospheric pressure. Three kinds of iron oxide/silica catalysts were prepared from ferric chloride, ferric nitrate and ferric hydroxide and the catalysts were characterized by X-ray fluorescence, X-ray diffraction and X-ray photoelectron spectroscopy and their activities were examined. The effective species of catalyst was found to be Fe2O3 on silica. Changing the iron starting materials affects the dispersity of iron oxide on silica, thereby resulting in a difference of catalytic activity. The catalyst originating from ferric hydroxide shows the highest dispersity and activity per unit atom of iron. The formation of a fine crystallite of iron oxide is important to increase the activity of the catalyst as is shown by the fact that catalytic activity is increased by decreasing the iron content of the catalyst.

5-Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 were obtained from the corresponding 1-aroyl-2-thiobiurets 2 by oxidative cyclization with bromine. 5-Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 can exist in two tautomeric forms-a lactam form and a lactim form. On the basis of the 13 C nmr spectra and additional experimental information, it has been established that the stable form, in which these compounds exist, is the lactam form

5-Aroylamino-2-methyl-2H-1,2,4-thiadiazol-3-ones 3 have been synthesized by oxidative cyclization of 1-aroyl-5-methyl-2-thiobiurets 2 with hydrogen peroxide in an alkaline solution. The needed 1-aroyl-5-methyl-2-thiobiurets 2 have been obtained through the addition of methylurea to the corresponding aroyl isothiocyanates.

In situ oxidation of cyclohexane to cyclohexanol and cyclohexanone was investigated with hydrogen peroxide produced from hydrogen and oxygen at a temperature of 30 °C and under atmospheric pressure. Three kinds of iron oxide/silica catalysts were prepared from ferric chloride, ferric nitrate and ferric hydroxide and the catalysts were characterized by X-ray fluorescence, X-ray diffraction and X-ray photoelectron spectroscopy and their activities were examined. The effective species of catalyst was found to be Fe2O3 on silica. Changing the iron starting materials affects the dispersity of iron oxide on silica, thereby resulting in a difference of catalytic activity. The catalyst originating from ferric hydroxide shows the highest dispersity and activity per unit atom of iron. The formation of a fine crystallite of iron oxide is important to increase the activity of the catalyst as is shown by the fact that catalytic activity is increased by decreasing the iron content of the catalyst.

5-Aroylamino-3H-1,3,4-thiadiazole-2-thiones 2 have been synthesized by acylation of 5-amino-3H-1,3,4-thiadiazole-2-thione 1. 5-Aroylamino-3H-1,3,4-thiadiazole-2-thiones can exist in two tautomeric forms — a thiol form and a thione form. On the basis of the 13C nmr spectra and additional experimental information, it has been established that the thione form is the stable form in which these compounds exist.

5-Amino-2H-1,2,4-thiadiazoline-3-one has been prepared from 2-thiobiuret through a oxidative cyclization under basic hydrogen peroxide condition. Lactam-lactim tautomerism of 5-amino-2H-1,2,4-thiadiazoline-3-one has been examined by spectroscopic methods and ab initio molecular orbital calculation. These results were shown that 5-amino-2H-1,2,4-thiadiazoline-3-one exists as lactam form. Reaction conditions for alkylating 5-amino-2H-1,2,4-thiadiazoline-3-one with alkyl halides in the presence of various bases were studied in DMF and -THF two phase system. base in DMF method gave best result in this investigation. The alkylation has been taken place at N-2 position. The identification of the product is confirmed by spectral data of IR, NMR and NMR and the comparison of authentic sample, 5-amino-2-methyl-1,2,4-thiadiazolidine-3-one, obtained from the oxidative cyclization of 5-methyl-2-thiobiuret.

5-Amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 can be synthesized from 5-amino-2H-1,2,4-thiadiazolin-3-one (1–1) via a selective acylation with an acid anhydride in pyridine. The 1H nmr spectral characteristics of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 is in particular, compared with 5-amino-2H-1,2,4-thiadiazolin-3-one (1–1) and 5-amino-2-alkyl-1,2,4-thiadiazolin-3-ones 1–2, 1–3. The 5-amino group of 2–1 appeared as two peaks in its 1H nmr spectrum, which merged to a single peak at a higher temperature, while those of compound 1–1, 1–2 and 1–3 appear only as a single peak. The restricted rotation of the C(5)-N(5) (at amino) bond of 5-amino-2-acetyl-1,2,4-thiadiazolin-3-one (2a-1) is about 14.5 Kcal/mol.

1,3-[5,5′-(1,2-Phenylenedimethylenedithio)bis(2,3-dihydro-2-oxo-1,3,4-thiadiazol-3-yl)]propane is prepared and its structure clearly established from spectroscopic data (IR, 1H and 13C NMR, and mass spectrometry) and X-ray crystallography.

5-Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 were obtained from the corresponding 1-aroyl-2-thiobiurets 2 by oxidative cyclization with bromine. 5-Aroylamino-2H-1,2,4-thiadiazol-3-ones 3 can exist in two tautomeric forms-a lactam form and a lactim form. On the basis of the 13 C nmr spectra and additional experimental information, it has been established that the stable form, in which these compounds exist, is the lactam form

5-Aroylamino-2-methyl-2H-1,2,4-thiadiazol-3-ones 3 have been synthesized by oxidative cyclization of 1-aroyl-5-methyl-2-thiobiurets 2 with hydrogen peroxide in an alkaline solution. The needed 1-aroyl-5-methyl-2-thiobiurets 2 have been obtained through the addition of methylurea to the corresponding aroyl isothiocyanates.

Transition metal complexes with peripheral sites capable of hydrogen-bonding or π-stacking interactions to form groups have recently been used as hosts to bind neutral guests, such as aliphatic amines, aromatic amines, hydrazines, DNA nucleobases, amino acids, and barbiturate. This form of host is referred to as a metalloreceptor. The construction of hosts with metal ions in the scaffold has allowed the binding of many structurally sophisticated guests. Consequently, the design and study of various metalcontaining macrocycles is one of the most active and interesting areas in modern supramolecular chemistry. Coordinate covalent bond formation offers new prospects for selective molecular recognition, anion transport, and catalytic activation of electron-rich organic and inorganic substrates. It has long been recognized that multiple complementary interactions between the host and guest are of vital importance in stabilizing host-guest complexes (e.g., the chelation effect). Investigations of host-guest interactions and inclusion phenomena as well as biomimetic studies have become interesting targets. To obtain stable, reversible adducts, there is still a clear need for neutral molecular receptors that are simple and versatile, while they are also selective. This recalls the first stages of enzymatic processes, which involve the formation of a metallo-enzyme-substrate complex. We sought to prepare macrocycles composed of 5-membered cytosine analogues and 1,3-benzenedimethanethiol.

Macrocycles containing two 2-imino-5-mercapto-2,3-dihydro-1,3,4-thiadiazole subunits linked to the 3- and 5-positions of the heterocycle unit were prepared by regiospecific alkylation of 5-amino-2,3-dihydro-1,3,4-thiadizole-2-thione and 2-acetylamino-5-alkylthio-1,3,4-thiadizoles, respectively. The structures of the macrocycles were established from 1 H and 1 3 C NMR, IR, MS spectrometries and elemental analyses. Moreover, the structure of the macrocycle 1,5-[5,5'-(1,3-phenylenedimethylenedithio)bis(2,3-dihydro-2-acetylimino-1,3,4-thiadiazol-2-yl)]-3-oxapentane (4b) was supported by X-Ray crystallography.

In the title compound (systematic name: {[(phenylformamido)carbonyl]amino}methanethioamide), C9H9N3O2S, both benzoyl and terminal thiourea fragments adopt transoid conformations with respect to the central carbonyl O atom. The benzoyl and thiobiuret groups are almost coplanar, making a dihedral angle of 4.40 (8)°. The molecular structure is stabilized by two intramolecular N—H...O hydrogen bonds. In the crystal, N—H...O and N—H...S hydrogen bonds link the molecules into a tape running along [101].

In the title compound, C12H12N6S4, the two terminal thiadiazole rings are twisted with respect to the central benzene ring, making dihedral angles of 54.28 (4) and 76.56 (3)°. The dihedral angle between the two thiadiazole rings is 27.77 (4)°. Intermolecular N—H...N hydrogen bonds stabilize the crystal packing, linking the molecules into a tape along thebaxis.