Volume 38, Issue 10

It is shown that the previously reported 1,3,2-dioxaborinium salts containing tricoordinated boron are in fact tetracoordinated coordination compounds. The same holds for the corresponding triflates.

5-Bromo-uracil (2) with chloro-diphenylphosphine and triethylamine gives 5-bromo-N(1),N(3)-bis(diphenylphosphino)-uracil (3). In moist acetone, 3 is hydrolyzed to 5-bromo-N(1)-diphenylphosphino-uracil (4). 3 reacts with n-butyllithium under rearrangement and, with HCl, under elimination of a PPh 2 -group, forms C(5)-diphenylphosphino-uracil (7a). Recrystallization of 7 a from ethanol yields the ethanol-1:1-adduct 7b. Heating of 7a in dimethylsulfoxide with D 2 O yields the N(1),N(3)-dideutero-C(5)-diphenylphosphino-uracil (7c). All compounds were characterized by infrared, Raman, 1 H, 31 P NMR and mass spectra. 7a shows a very small antitumor activity.

Spin-spin and spin-lattice relaxation times of nuclei 69,71 Ga, 27 Al, 14 N in anions [MCl n Br 4-n ]-and the solvate complexes [M(CH 3 CN) 6 ] 3+ , produced from dissolution of MCl 3 and MBr 3 in the mixture CH 3 CN + CH 3 NO 2 (M = Ga, Al), are measured in the temperature range from -40 up to + 70 °C. It is shown that nuclear spins of 69,71 Ga, 27 Al relax in the anionic and cationic complexes by means of the second-kind scalar and quadrupole relaxation mechanisms (due to the relaxation of the nuclei 35,37 Cl, 79,81 Br, 14 N). The complexes [MCl n Br 4-n ]-and [M(CH 3 CN) 6 ] 3+ in the investigated solutions are inert and do not undergo exchange processes in the NMR time scale. The scalar spin coupling constants in [M(CH 3 CN) 6 ] 3+ are determined from the scalar contribution to the relaxation rate of 69,71 Ga, 27 Al, and the measured relaxation time of 14 N in the solvate complex; the results are J( 69 Ga- 14 N) = 59 ± 5 Hz, J( 71 Ga- 14 N) = 74 ± 6Hz, J( 27 Al- 14 N) = 22 ± 2Hz.

The reaction of the 1,2,4-trithia-3,5-diborolane system with alkynes does not give 1,3,2-dithiaboroles, as suggested earlier [1, 2], but the previously unknown 1,2,3-dithiaboroles. With organic isocyanates and di-isopropylcarbodiimide, 1,2-dithia-3-bora-4-azacyclopentanones-( 5) and -thiones-(5), respectively, were isolated. The latter systems are isomers of the 5-methyl-1,4-dithia-2-aza-5-boracyclopentanones-(3) and -thiones-(3), which had been previously assumed as reaction products. The structures of 3-diethylamino-4,5- diphenyl -1,2,3 -dithiaborole - (4) (18), 3-(2,6-dimethylphenyl)-amino-4,5-diethyl-1,2,3-dithiaborole-( 4) (31) and 2-diphenylamino-1,3,2-dithiaborole-(4) (32) have been determined by X-ray diffraction. 18 is monoclinic, space group P2 1 , a = 627.8(2), b = 1218.8(2), c = 1158.6(3) pm, β = 97.35(2)° and Z = 2. 31 is monoclinic, space group C2/c, a = 1475.9(5), b = 898.6(3), c = 2434.7(9) pm, β = 102.71(3)° and Z = 8. 32 is orthorhombic, space group Aba 2, a = 2557.3(8), b = 1748.5(5), c = 935.2(2) pm, Z = 12. 1 H, 11 B, 13 C NMR, mass and IR spectra are also reported and discussed.

It is shown by X-ray structure determination of its acetyl derivative, that the vic. triketone 2,2,6,6-tetramethylpiperidine-3,4,5-trione reported in the literature really is 2-(1-hydroxy-1-methylethyl)-5,5-dimethyl-4,5-dihydropyrrol-3,4-dione. The UV-PE-spectra of both compounds and their electronic structures are interpreted by means of MO calculations. A mechanism yielding these pyrroline-1 derivatives instead of piperidine ketones is suggested, the formerly assigned structures of precursors are corrected.

The influence of different substituents on the electrochemical reduction of benzylidene-malononitriles in benzonitrile at platinium electrodes has been investigated using DC-voltametry, cycl. voltametry and coulometry.

During syntheses using the phthalimide rest in liquid, ethanolic or aqueous ammonia, phthalamides, phthalimides or phthalamic acids are formed depending on reaction condi-tions and work-up. As demonstrated by the synthesis of the title compound via hydrolysis of 4 with aqueous ammonia, dipolar ions of phthalamic acids are obtained if the phthal-imide-N substituent is sufficiently basic. The crystal structure of 5 • 4H2O has been determined and refined until R = 0.0878. It shows a vast system of hydrogen bonds.

Photolysis of argon-matrix isolated 4,5-bis(carbomethoxy)-1,2,3-thiadiazole with λ = 254 or 265 nm resulted in the almost quantitative formation of bis(carbomethoxy)-thiirene (3g). Photolysis of 3g could only be carried out by long irradiation times at short wavelength λ = 210 nm and resulted mainly in extensive fragmentation instead of the formation of bis(carbomethoxy)thioketene, confirming earlier predictions that substituents, especially electron-withdrawing ones, should stabilize the thiirene ring. Methylcarboethoxy and methylacetylthioketene were obtained, however, in the argon-matrix photolysis or flow thermolysis of 4-methyl-5-carboethoxy-or 4-carboethoxy-5-methyl-1,2,3-thiadiazole and 4-acetyl-5-methyl-1,2,3-thiadiazole, respectively.

In order to elucidate some aspects of the mechanism of radical-induced strand break formation in DNA, the γ-radiolysis of N 2 O-saturated aqueous solutions of 2′-deoxycytidine-5′-phosphate has been studied as a model system. At pH 4 it has been observed that upon OH attack at the sugar moiety phosphate (G ≈ 0.6) and cytosine (G = 1) are released and the following cytosine-free sugars are formed: 2,5-dideoxypentos-3,4-diulose, 1 (G = O.2 2 ), 2-deoxy-pentos-4-ulose, 2 (G = 0.1 8 ), 2-deoxy-pentos-4-ulose-5-phosphate, 3 (G=0.06), 2-deoxypentonic acid-5-phosphate and its lactone, 5 (G ≈ 0.5). Some 2-deoxyribose-5-phosphate, 4 is also formed. Upon addition of H 2 O 2 (up to 10 -2 M) prior to irradiation, G(1) is drastically reduced without giving rise to another cytosine-free product. G(3) increases at the expense of G(2). G (4 + 5) also increase upon H 2 O 2 addition. The formation of these products and the change of their G values as a function of H 2 O 2 concentration are discussed in the light of well-documented radical reactions of carbohydrates and related compounds. The precursor of 1 has been considered to be the radical at C-3′, that of 2 and 3 the radical at C-4′ and that of 5 the radical at C-1′. Product 4 is thought to arise from a radical-induced destruction of the cytosine moiety. These primary radicals which may undergo rearrangement, or eliminate phosphate, are readily oxidised by H 2 O 2 , a reaction which leads to the change of product distribution mentioned above.

Nonpolar aromatic nematogens useful in mixtures for high performance matrix-addressed twisted nematic displays were synthesized. Nematic phases were obtained by introducing lateral halo-substituents in purely smectic biphenyls and phenyl pyrimidines. Because of their chemical stability, low viscosity and negative dielectric anisotropy, the substituted biphenyls can also be used in mixtures of negative dielectric anisotropy which are needed for the homeotropic nematic and guest-host displays with positive contrast. The effect of lateral halo-substituents on the mesomorphic properties of rod like molecules is discussed.

Using a conception given in [1, 3] for single ionic solvation and redox reactions the electron affinities (EA) of halogens are calculated from calorimetric data of their reactions with methyleneblue radical giving the values 8.81 eV; 8.23 eV; and 7.16 eV for Cl, Br and I, respectively. For iodine EA is also obtained from the reaction enthalpy of the reaction between iodide and Mg-porphyrine cation radical. EA calculated from electrochemical standard potentials are only approximately 0.2 eV higher than found from calorimetric data except for iodine, the standard potential of which could be influenced by I3-. The disagreement of the EA values given in the literature and those presented in this work is mainly caused -to the author's opinion -by a different interpretation of single ionic solvation and the size of ionic radii in solutions. From experimental data [1,3] solvation of anions is regarded as an energy consuming process which is understood as the overall repulsion between the anionic charge and the outer sphere electrons of solvent molecules. For calculation of the solvation energy according to the Born equation different radii have to be used: in the case of anions, the radius is composed of the radius of anions in the crystals extended by the average radius of a solvent molecule, in the case of cations -the solvation of which is an energy supplying process -the radius of atoms must be taken. On this basis the ionisation energy of tetra-methyl-p-phenylenediamine is calculated from calorimetric data for the reaction with bromine. As other examples the reaction enthalpies of the reactions of chlorine with methyleneblue radical, Li, Na, K, Cs, Be, Ca, La, Al and Zr are calculated in the gas phase as well as in water and compared with experimental ⊿G-values obtained from electrochemical standard-potentials. Excellent agreement for all selected examples is found. The discussion includes electron absorption energies of anions and solvation of ionic crystals in a solvent.

Solasodine on reaction with BrCN yielded two isomeric cyanamides in a ratio of 3:1, which have been characterised as C-22 configurational isomers, N-cyanosolasodine (22 R, 25 R) IIA and N-cyanosolasodine (22 S, 25 R) II B on the basis of 1 H and 13 C NMR studies. The same reaction with piperidine, yielded its cyanamide, the 13 C NMR of which is also reported.

Alkyl-pyrryl-carbinols are cyclised in acidic medium to meso-tetraalkyl-porphyrins.

We describe the preparation of alkylsubst. benzodioxoles, -dioxane, -dioxepine and dioxocine 2a-e. The can be subjected to a Vilsmeyer-formylation, yielding the aldehydes 3 a-e. Treatment of 3 a-e with performic acid leads to the phenoles 4 a-e in a Baeyer-Villiger-Oxidation. Using Zincchloride as a catalyst the chromanes 5 a-j can be obtained by reaction of 4 a-e with either prenylbromide or phthylbromide.

AeHuIFN αA(30-43)-( 123-137)-NH 2 , Ac-Leu-Lys-Asp-Arg-His-Asp-Phe-Gly-Phe-Pro-Gln-Glu-Glu-Phe-Phe-Gln-Arg-Ile-Thr-Leu-Tyr-Leu-Lys-Glu-Lys-Lys-Tyr-Ser-Pro-NH 2 was synthesized toward encompassing the “active site” of the interferons. The design of this 29-amino acid peptide was based on considerations of homology between the different interferons and on combining two regions of interferons, and on known and predicted structural features. The peptide was characterized by amino acid analysis, thin layer chromatography in several systems, and by HPLC. As tested, the peptide neither showed antiviral activity nor blocked antiviral activity of interferon, indicating that the active site was not encompassed or that interferon may not be a sychnological peptide.

Analogs of the luteinizing hormone releasing hormone (LHRH) having a moiety (D-Qal-) of β-(3-quinolyl)-D-α-alanine were synthesized toward more effective inhibitors of ovulation. [N-Ac-pCl-D-Phe 1,2 , D-3-Pal 3 , D-3-Qal 6 , D-Ala 10 ]-LHRH was the most effective, and had an antiovulatory activity of 40% at 1 μg/rat. D-3-Qal 6 was as effective as D-Trp 6 in combination with N-Ac- 3 ⊿Pro 1 , pF-D-Phe 2 , D-Trp 3 . D-Arg 6 was superior to D-3-Qal 6 ) in combination with N-Ac-pCl-D-Phe 1,2 , D-Trp 3 (or D-3-Pal 3 ), D-Ala 10 . The introduction of D-3-Qal 3 , D-His 3 and D-Arg 3 in comparable analogs caused substantial loss of activities.

New insights into the autocatalytic primary reaction step of the formose reaction are obtained by using soluble calcium hydroxide bismethylene glycolate complexes for kinetic investigations in homogeneous phase. The reaction kinetics follows between 20% and 80% formaldehyde consumption a nonlinear rate equation. Specific co-catalytic activities are determined for the most important intermediates and end products of the formose reaction. By correlation of the kinetic results with solubility experiments, ultraviolet, 13 C NMR spectroscopic measurements and rates of oxidation and acid formation, a mechanism for the autocatalytic primary reaction is given. The main catalytic effects for the formaldehyde activation are caused by calcium enediolate complexes in an autocatalytic cycle and competition with the Cannizzaro and oligomerisation reaction. Further, but less probable mechanisms are also discussed.

By means of liquid chromatographic analysis, UV, 13 C NMR and GC-MS spectroscopy it is possible to determine quantitatively the most important intermediate and final products of the formose reaction. As stable main products xylose, glucose and dendroketose, as stable side products ribose, lyxose, arabinose, mannose, dendroaldose, fructose and sorbose are identified. Instable intermediates are glycolaldehyde, glycerolaldehyde, dihydroxiacetone, erythrose, threose and pentuloses. Cannizzaro reaction, oligomerization and the primary formose reaction are catalyzed by a calcium hydroxide bismethylene glycolate complex.

Polysiloxanes with chiral peptide side chains have been synthesized and used as stationary phases in gas chromatography. With these phases amino acid enantiomers can be separated as N-acyl esters. Due to temperature stability up to 230 °C all protein amino acids can be separated and the racemization of synthetic biologically active peptides controlled. The phases can be used to assign the absolute configuration of amino acids. A variety of other classes of compounds can be separated into their enantiomers using the chiral polysiloxanes, like hydroxy acids, sulfoxides, phosphorous compounds, glycols, atrop isomers, amines and alcohols. Various applications of these phases are described including investigations of enantiomer selectivity in nature.

Mg(SiMe 3 ) 2 · DME can be prepared in high yields by reaction of magnesium powder with Hg(SiMe 3 ) 2 in 1,2-dimethoxyethane in a supersonic bath.

The photochemical oxidation of tetraline by dioxygen is catalyzed by ferric acetylacetonate (iron(III) 2,4-pentadionate), the reaction rate increasing markedly with temperature. The rate-determining step of the photochemical oxidation is presumably a catalyzed thermal reaction.

(η 3 -Allyl)(η 5 -cyclopentadienyl)palladium reacts with bis(diphenylphosphino)maleic anhydride to form a complex in which the C 5 H 5 ligand is inserted into a P-C bond of the phosphine ligand. Reaction of this compound with iodine leads to a new type of phosphino ligand. The structure is studied by X-ray crystal structure analysis.

PPh 4 [MoNCl 4 ] is isotypic with AsPh 4 [MoNCl 4 ], crystallizing in the space group P4/n. The lattice constants a = 1277.6 and c = 765.4 pm are slightly smaller for the PPh 4 + salt; the difference can be explained by the shorter bond lengths P-C vs. As-C. The conformation angles of the phenyl groups are nearly equal in both compounds.

Single crystals of (P(C 6 H 5 ) 4 ) 2 [Sn(N 3 ) 6 ] were prepared by the reaction of SnCl 2 with AgN 3 or NaN 3 in a CH 2 Cl 2 suspension in the presence of PPh 4 Cl. The crystal structure was solved with X-ray methods (space group P1̅, Z = 1, a = 1021, b = 1064, c = 1247 pm, α = 88.1°, β = 74.9°, γ = 68.6°, 3691 independent reflexions, R = 0.039). The structure consists of PPh 4 ⊕ cations and anions [Sn(N 3 ) 6 ] 2⊖ . The symmetry of the hexazidostannate is C i , the N 3 -groups are covalently bonded to the Sn-centre with ∢SnNN between 119 and 126°.

Electronegativities, Group IV Elements Electronegativities for Group IV elements A have been estimated from the bond lengths observed in AX 2 and AX 4 molecules (X = F, Cl, Br). The order of electronegativities established by this method is χ C > χ Ge > χ sn > χ Si.

Tetramethyldistibane reacts with equimolar amounts of di-p-tolylditelluride to yield quantitatively p-tolyltellurodimethylstibane, the first molecule with a Te-Sb bond. The compound has been characterised by elemental analysis and by NMR and mass spectra.

The 1 -azaadamantane 1 is stereoselectively reduced to the trialcohol 2, as shown spectroscopically by 1 H NMR 4 J(W) coupling and chemically by reaction with trimethoxymethane to the heterodiamantane 4.

A new indole alkaloid, hyderabadine, has been isolated from the leaves of Ervatamia coronaria to which structure 1 has been assigned.