Search

The asymmetric unit of the title compound, C(12)H(10)N(4)O(2)S(4)·2C(2)H(6)OS, contains one half of the p-xylene mol-ecule and one dimethyl sulfoxide mol-ecule. The p-xylene mol-ecule is located about a crystallographic inversion centre. In the mol-ecule, the thia-diazole and benzene rings are almost perpendicular to one another, with a dihedral angle of 88.95 (6)°. In the crystal, an N-H⋯O hydrogen bond is observed between the two components. The dimethyl sulfoxide mol-ecule is disordered over two orientations with an occupancy ratio of 0.879 (1):0.121 (1).

In the title compound, C4H6N2OS2, the dihedral angle between the five-membered heterocyclic ring and the plane of the ethoxy group is 4.9 (2)°. The 1,3,4-thiadiazole-2-thione unit is planar, with an r.m.s. deviation of 0.011 Å from the corresponding squares plane defined by the seven constituent atoms. In the crystal, pairs of N—H...S hydrogen bonds link the molecules into inversion dimers.

In the title compound, C4H5N3OS2·2C2H6OS, the five-membered heterocyclic ring and the N—(C=O)—C plane of the acetamide group are essentially co-planar, with a dihedral angle of 1.25 (3)°. Intermolecular N—H...O hydrogen bonds between the acetamide compound and the dimethyl sulfoxide molecules stabilize the crystal structure. The two dimethyl sulfoxide molecules are each disordered over two positions with occupancy ratios of 0.605 (2):0.395 (2) and 0.8629 (18):0.1371 (18).

Two mol­ecules of the title compound, 3,5,15,17-tetra­thia-7,13,24,25-tetra­aza­tetra­cyclo­[17.3.1.14,7.113,16]­penta­cosa-1(23),4(24),16(25),19,21-penta­ene-6,14-dione, C16H16N4O3S4, having slightly different hollow and curved conformations, form the asymmetric unit. Each mol­ecule provides an internal cavity of cage-like shape to form a host–guest complex.

The title compound, C14H16N4O8S4, has crystallographic C2 symmetry with half a molecule in the asymmetric unit and a dihedral angle of 58.7 (1)° between the two planar 1,3,4-thiadiazole five-membered rings of the macrocyclic, giving the molecule a twisted conformation.

Macrocyclic ligands containing two 5-mercapto-3H-1,3,4-thiadiazoline-2-one groups and one 1,3-benzenedimethanethiol group, which served to link the 2- and 5-positions of the heterocycle unit and chelate palladium ion, respectively, were synthesized by regiospecific S-alkylation of 5-ethoxy-3H-l,3,4-thiadiazoline-2-thione. The structures of the resulting metalloreceptors were established using 1 H and 13 C NMR, FTIR spectroscopy, MS spectrometry, and elemental analysis. The molecular recognition ability of the metalloreceptors was examined against DNA/RNA nucleobases and acetanilide. The complexation strength of both compounds increased in the order acetanilide/uracil/thymine < adenine < cytosine.

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 synthesis of two new acyclic nucleoside analogs, 2-(2′,3′-dihydroxypropyl)-5-amino-2H-1,2,4-thiadiazol-3-one (1) and 3-(2′,3′-dihydroxypropyl)-5-amino-3H-1,3,4-thiadiazol-2-one (2), is reported. The first compound, 1, was obtained by reaction of 3-chloro-1,2-propanediol with the sodium salt of 5-amino-2H-1,2,4-thiadiazol-3-one (3) in anhydrous dimethylformamide. Similarly, 5-amino-3H-1,3,4-thiadiazol-2-one (4) reacted with 3-chloro-1,2-propanediol to give 2. The thiadiazole 4 was prepared by condensation-cyclization of hydrazothiodicarbonamide (9).

Macrocycles containing two 5-amino-3H-1,3,4-thiadiazolin-2-ones linking the 3- and 5-positions of the heterocycle unit and one 1,3-benzenedimethanethiol were prepared via the regiospecific N-alkylation of 5-amino-3H-1,3,4-thiadiazolin-2-one. The 1,3-benzenedimethanethiol sites chelated to palladium metal ion to give an organopalladium metalloreceptor. The structures of the macrocycle and metalloreceptor were established using 1 H and 1 3 C NMR, IR, and MS spectrometry. The molecular recognition of the metalloreceptor (5) was examined for some DNA/RNA nucleobases using 1 H NMR spectrometry. The complexation ability increased in the order uracil/thymine < adenine < cytosine/imidazole.

Absract- The oxidative cyclization of dithiobiuret under basic conditions (NaOH-H 2 O 2 or CH 3 CO 3 H) afforded bis(5-amino-1,2,4-thiadiazolyl) 3,3'-disulfide (5), oxidative dimer form of 5-amino-3-mercapto-1,2,4-thiadiazole (3b). The theoretical tautomeric study (ab initio calculations) shows that the most stable tautomeric form of 3 is 5-amino-3-mercapto-1,2,4-thiadiazole (3b) among the four possible tautomers. Thus, 3b is speculated as an intermediate of the formation of the compound (5).

2,4-Dimethoxy- and 2,4-dibenzyloxy-5-lithiopyrimidines, obtained from the corresponding substituted 5-bromopyrimidines, react with trimethylsilyl chloride or trimethylstannyl chloride to give the appropriate 5-trimethylsilyl or 5-trimethylstannyl derivatives. The following compounds were synthesized by this reaction sequence: 2,4-dimethoxy-5-trimethylsilylpyrimidine (2), 2,4-dibenzyloxy-5-trimethylsilylpyrimidine (3), 2,4-dimethoxy-5-trimethylstannylpyrimidine (4), and 2,4-dibenzyloxy-5-trimethylstannylpyrimidine (5). Similarly, 6-chloro-2,4-dimethoxypyrimidine was converted into the 5-lithio derivative which subsequently gave 6-chloro-2,4-dimethoxy-5-trimethylsilylpyrimidine (6) and 6-chloro-2,4-dimethoxy-5-trimethylstannylpyrimidine (7). In a new modified synthesis of 5-trimethylsilyluracil (1), 2,4-dibenzyloxy-5-trimethylsilylpyrimidine (3) was smoothly converted into 1 by reaction with trimethylsilyl iodide.

The synthesis of two new acyclic nucleoside analogs, 2-(2′,3′-dihydroxypropyl)-5-amino-2H-1,2,4-thiadiazol-3-one (1) and 3-(2′,3′-dihydroxypropyl)-5-amino-3H-1,3,4-thiadiazol-2-one (2), is reported. The first compound, 1, was obtained by reaction of 3-chloro-1,2-propanediol with the sodium salt of 5-amino-2H-1,2,4-thiadiazol-3-one (3) in anhydrous dimethylformamide. Similarly, 5-amino-3H-1,3,4-thiadiazol-2-one (4) reacted with 3-chloro-1,2-propanediol to give 2. The thiadiazole 4 was prepared by condensation-cyclization of hydrazothiodicarbonamide (9).

The ground-state dipole moments of seven biologically important purines (purine, 6-chloropurine, 6-mercaptopurine, hypoxanthine, theobromine, theophylline and caffeine) were determined at 25°C in acetic acid (all the above compounds with the exception of purine) and in ethyl acetate (purine, theophylline and caffeine). Because of its low solubility, it was not possible to measure the dipole moment of uric acid. The first excited singlet-state dipole moments were obtained on the basis of the Bakhshiev and Chamma—Viallet equations using the variation of the Stokes shift with the solvent dielectric constant-refractive index term. The theoretical dipole moments for all the purines listed above and including uric acid were calculated by combining the use of the PPP (π-LCI-SCF-MO) method for the π-contribution to the overall dipole moment with the σ-contribution obtained as a vector sum of the σbond moments and group moments. The experimental and theoretical values were compared with the data available in the literature for some of the purines under study. For several purines, the calculations were carried out for different tautomeric forms. Excited singlet-state dipole moments are smaller than the ground-state values by 0.8 to 2.2 Debye units for all purines under study with the exception of 6-chloropurine. The effects of the structure upon the ground- and excited-state dipole moments of the purines are discussed.