Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Struktur des porphinoiden Ligandsystems

Factor F430 from Methanogenic Bacteria: Structure of the Porphninoid Ligand System A structure is proposed for F430M, a non-cristalline methanolysis product of isolates of the nickel-containing, porphinoid factor F430 from Methanobacterium thermoautotrophicum. Crucial to the structure determination are five incorporation experiments with M. thermoautotrophicum (strain Marburg) in which the specifically mono-¹³C-labeled biosynthetic precursors (2-¹³C), (3-¹³C), (4-¹³C)-, (5-¹³C) ALA (ALA = δ-amino-levulinic acid) and L-(methyl-¹³C)methionine were incorporated into F430 with high efficiency. The ¹³C-NMR,-spectra of the specifically labeled F430M samples derived therefrom, together with the UV./VIS. spectral data of F430M, contain all the information necessary for the deduction of the constitution of the F430M chromophore, assuming the established pattern of porphinoid biosynthesis to be operative in F430 biosynthesis. ¹H-NMR. spectroscopy and, in particular, ¹H-NMR.-NOE-difference spectroscopy corroborates and completes the constitutional assignments and, furthermore, makes possible an almost complete derivation of the molecule's relative configuration. Schemes 3 and 4 summarize the results of ¹H-NMR. spectroscopy, presenting them within the context of the proposed structure for F430M. The assignment of absolute configuration implied in the formula is given preference because of F430M's very close structural and (assumed) biosynthetic relationship to sirohydrochlorin and vitamin B₁₂ (with respect to ring C, the assignment is based on degradative evidence). According to the proposed structure, the nickel complex F430M possesses an uroporphinoid (Type III) ligand skeleton with an additional carbocyclic ring and a chromophore system not previously encountered among natural porphinoids. It can be considered to be a (tetrahydro) derivative of the corphin system, combining structural elements of both porphyrins and corrins.     

Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Absolute Konfiguration

Factor F430 from Methanogenic Bacteria: Absolute Configuration Experiments on F430M ( 2 ) aiming at a potentially biomimetic, reductive reconstruction of the F430 ( 1 ) chromophore from corresponding pyrrocorphinate intermediates provided us with F430 derivatives which contain an isobacteriochlorinate chromophore system similar to the one occurring in sirohydrochlorin ( 3 ) (cf. the Scheme). Comparison of their CD spectra with the-CD spectrum of nickel( II )-sirohydrochlorinate octamethyl ester demonstrates that the absolute configurations of factor F430 and sirohydrochlorin in the region of rings A and B are the same.     

Zur Kenntnis des Faktors F430 aus methanogenen Bakterien: Über die Natur der Isolierungsartefakte von F430, ein Beitrag zur Chemie von F430 und zur konformationellen Stereochemie der Ligandperipherie von hydroporphinoiden Nickel(II)-Komplexen

Factor F430 from Methanogenic Bacteria: On the Nature of the Isolation Artefacts of F430, a Contribution to the Chemistry of F430 and the Conformational Stereochemistry of the Ligand Periphery of Hydroporphinoid Nickel(II) Complexes Factor F430 ( 1 ), a coenzyme from methanogenic bacteria, when heated in aqueous solution isomerizes to 12,13-di-epi-F430 ( 5 ) via 13-epi-F430 ( 3 ). The equilibrium mixture of the three F430 isomers in aqueous phosphate buffer solution (pH 7, 100°) contains 88 % of 5 , 8 % of 3 , and 4 % of 1 (Scheme 1). The structural assignment for the F430 isomers rests on FAB-MS-, UV/VIS-, ¹H- and ¹³C-NMR spectra of their pentamethyl esters. Chemical proof for the double epimerization at the two chiral centers of F430's ring C was provided by ozonolytic degradation of the di-epimer to give a ring-C-derived succinimide derivative that was shown to be the enantiomer of the one previously obtained by ozonolysis of F430M (see Scheme 2). The two F430 ring-C epimers 3 and 5 are the isolation artefacts described in the earlier F430 literature. F430 is susceptible to autoxidation in air and the product, that absorbs at 560 nm, was shown to be the 12,13-didehydro derivative 8 of F430 by spectroscopic characterization of its pentamethyl ester 9 . The dehydrogenation product 8 can be diastereoselectively reduced with Zn in AcOH to give natural F430 as the main product rather than the thermodynamically more stable F430-di-epimer (Scheme 3). In the double epimerization of F430, the two ring-C side chains change from a trans-quasi-diaxial arrangement to the (locally) enantiomorphic position in which the same side chains are again in a trans-quasi-diaxial arrangement. This equilibrium paradox as well as the kinetic diastereoselectivity of the reduction of 12,13-didehydro-F430 ( 8 ) are rationalized to be consequences of the general phenomenon documented earlier (see the preceding paper) according to which hydroporphinoid Ni(II) complexes all show a characteristic conformational ruffling of their ligand system due to the tendency of the (small) Ni(II) ion to contract the size of the ligand's central coordination hole (see Fig. 5 and 6).     

Coenzyme F430 from Methanogenic Bacteria: Detection of a Paramagnetic Methylnickel(II) Derivative of the Pentamethyl Ester by 2H-NMR Spectroscopy

A methylnickel(II) derivative of coenzyme F430 ( 1 ) was proposed as an intermediate in the enzymic process catalyzed by methyl-CoM reductasc. Indirect evidence points to formation of CH₃–F430M^II in the reaction of F30M¹ (obtained from F430M^II ( 2 )) with eleclrophilic methyl donors. The results presented here show, that such a compound does exist. A paramagnetic CD₃–Ni^II derivative 5b of the pentamethyl ester 2 (F430M) of coenzyme F430 was prepared by in situ methylation with (CD₃)₂Mg and characterized by its isotropically shifted ²H-NMR spectrum. At ?40°, the very broad D-signal of the axially coordinated CD₃ group is found at ?490 ppm. Comparison with the ²H- and ¹H-NMR spectra of mcthyl(tetramethylcyclam)nickel(II) derivatives 4 ([Ni^II(CH₃))(tmc)]CF₃SO₃ ( 4a ) is the only isolated CH₃–Ni derivative of a N₄macrocyclic Ni^II complex' shows that the large isotropic shift to high field is characteristic for a Me group axially bound to the Ni center. The temperature dependence of the isotropic shift of the CD₃–Ni group in both 4b and 5b follows Curie's law and yields ²H hyperfine coupling constants of ?0.65 ( 4b ) and ?0.85 MHz ( 5b ), respectively. The ¹H-NMR spectrum indicates that, in contrast to the five-coordinate monochloro complex [Ni^IICl(tmc)]⁺, intermolecular exchange of the axial ligand in [Ni^II(CH₃)(tmc)]⁺ 4a is either slow at the NMR time scale or does not occur at all.     

Compounds with Cluster Cations together with Cluster Anions [(M6X12)(EtOH)6]2+ besides [(Mo6Cl8)Cl4X2]2– (M = Nb,Ta; X = Cl,Br) – Synthesis and Crystal Structures

Compounds consisting of both cluster cations and cluster anions of the composition [(M₆X₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₄X₂] · n EtOH · m Et₂O (M = Nb, Ta; X = Cl, Br) have been prepared by the reaction of (M₆X₁₂)X₂ · 6 EtOH with (Mo₆Cl₈)Cl₄. IR data are given for three compounds. The structures of [(Nb₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 3 EtOH · 3 Et₂O 1 and [(Ta₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 6 EtOH 2 have been solved in the triclinic space group P1 (No. 2). Crystal data: 1 , a = 10.641(2) Å, b = 13.947(2) Å, c = 15.460(3) Å, α = 65.71(2)°, β = 73.61(2)°, γ = 85.11(2)°, V = 2005.1(8) ų and Z = 1; 2 , a = 11.218(2) Å, b = 12.723(3) Å, c = 14.134(3) Å, α = 108.06(2)°, β = 101.13(2)°, γ = 91.18(2)°, V = 1874.8(7) ų and Z = 1. Both structures are built of octahedral [(M₆Cl₁₂)(EtOH)₆]²⁺ cluster cations and [(Mo₆Cl₈)Cl₆]^2– cluster anions, forming distorted CsCl structure types. The Nb–Nb and Ta–Ta bond lengths of 2.904 Å and 2.872 Å (mean values), respectively, are rather short, indicating weak M–O bonds. All O atoms of coordinated EtOH molecules are involved in H bridges. The Mo–Mo distances of 2.603 Å and 2.609 Å (on average) are characteristic for the [(Mo₆Cl₈)Cl₆]^2– anion, but there is a clear correlation between the number of hydrogen bridges to the terminal Cl and the corresponding Mo–Cl distances.     

Derivatives of Coenzyme F430 with a Covalently Attached α‐Axial Ligand. Part II

Coenzyme F430 pentamethyl ester 2 was partially hydrolyzed to a mixture of the five F430 tetramethyl esters 7 – 11 , which were separated by HPLC and identified by means of a full NMR characterization. The tetramethyl ester with a free COOH group at the side chain at C(3) of F430 was coupled to the N‐terminus of the peptidic spacer? ligand construct 12 selected and studied as described before. The UV/VIS and NMR spectra in CH₂Cl₂/3,3,3‐trifluoroethanol 6 : 1 show that the new derivative, the Ni^II(3³‐dehydroxy‐8³,12²,13³,18²‐tetra‐O‐methyl‐F430‐3³‐yl)‐L ‐prolyl‐L ‐prolyl‐N^π‐methyl‐L ‐histidine methyl ester ( 13 ), is an intramolecular, pentacoordinate, paramagnetic complex. In the same solvent system, the parent 3³,8³,12²,13³,18²‐penta‐O‐methyl‐F430 ( 2 ) is four coordinate and diamagnetic even in the presence of equimolar 1H‐imidazole. Protonation of the axially coordinating histidine residue of 13 gave the diamagnetic tetracoordinate base‐off form, which allowed us to establish the constitution of 13 by NMR.     

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

It is shown that azulene ( 1 ) and dimethyl acetylenedicarboxylate (ADM) in a fourfold molar excess react at 200° in decalin to yield, beside the known heptalene- ( 5 ) and azulene-1,2-dicarboxylates ( 6 ), in an amount of 1.6% tetramethyl (1RS,2RS,5SR,8RS)-tetracyclo[6.2.2.2^2,50^1,5]tetradeca-3,6,9,11,13-pentaene-3,4,9,10-tetracarboxylate(‘anti’-7) as a result of a SHOMO (azulene)/LUMO(ADM)-controlled addition of ADM to the seven-membered ring of 1 followed by a Diels-Alder reaction of the so formed tricyclic intermediate 16 (cf. Scheme 3) with a second molecule of ADM. The structure of ‘anti’-7 was confirmed by an X-ray diffraction analysis. Similarly, the thermal reaction of 5,7-dimehtylazulene ( 3 ) with excess ADM in decalin at 120° led to the formation of ca. 1% of ‘anti’- 12 , the 7,12-dimethyl derivative of‘anti’-7, beside of the corresponding heptalene- 10 and azulene-1,2-dicaboxylated (cf Scheme 2). The introduction of Me groups at C(1)and C(3)of azulene ( 1 ) and its 5,7-dimethyl derivative 3 strongly enhance the thermal formation of the corresponding tetracyclic compound. Thus, 1,3-dimethylazulene ( 2 ) in the presence of a sevenfold molar excess of ADM at 200° yielded 20% of ‘anti’- 9 beside an equal amount of dimethyl 3-mehtylazulene-1,2-dicarboxylate ( 8 ;cf. Scheme 1), and 1,3,5,7-tetramethylazulene ( 4 ) with a fourfold molar excess of ADM AT 200° gave a yield of 37% of‘anti’- 15 beside small amount of the corresponding heptalene- 13 and azulene-1,2-dicarboxylates 14 (cf.Scheme 2).     

Transition metal ion complexes of theS-methyldithiocarbazate prepared from 2-acetylpyridine

Summary Metal ion complexes of 2-acetylpyridineS-methyldithiocarbazate, HNNS, have been prepared and spectrally characterised. Preparations in EtOH yield complexes in which the deprotonated ligand, NNS, is complexedvia its pyridyl nitrogen, azomethine nitrogen, and thione sulphur. The stoichiometries are: [M(NNS)₂]X (M=Fe³⁺, Co³⁺ and X=ClO ₄ ^– , [FeCl₄]^–, BF ₄ ^– , 1/2 [CoCl₄]^2– and 1/2 [CoBr₄]^2–), [M(NNS)X] (M=Ni²⁺, Cu²⁺ and X=Cl^–, Br^–), [Cu(NNS)H₂O]BF₄ and Ni(HNNS)(NNS)F(EtOH)]BF₄. The spectral (i.e., i.r., u.v.-vis.-n.i.r. and e.s.r.) and physical properties of these complexes are compared to those of theS-methyldithiocarbazates of 2-formylpyridine and 2-acetylpyridineN-oxide, as well as the related thiosemicarbazones prepared from 2-acetylpyridine. Thermal studies of the nickel(II) complexes indicate that the nature of thermal decomposition of coordinated NNS is different from that of HNNS.     

EFFECTS OF 2,5-DIBROMO-3-METHYL-6-ISOPROPYL BENZOQUINONE (DBMIB) ON PHOTOCHEMICAL EVENTS IN RHODOSPIRILLUM RUBRUM*

Abstract. The quinone antagonist dibromothymoquinone (2,5-dibromo-3-methyl-6-isopropyl benzoquinone, DBMIB)? was used to inhibit early photochemical changes in chromatophores of the photo-synthetic bacterium, Rhodospirillum rubrum. With continuous illumination with near infrared light, we observed an approximately threefold decrease in efficiency of P865⁺ formation at 100–200 μM DBMIB as measured by absorbance changes at 605 or 430 nm. However, with continuous illumination of several seconds duration, maximal absorbance changes were observed. At low concentrations (1–10 μM) of DBMIB, a decrease in the decay rate of the ΔA₄₃₀ or ΔA₆₀₅ was observed. Using a short (2–10 μs), low intensity light pulse for excitation, we observed that DBMIB inhibits P865⁺ formation. The concentration dependency of this inhibition corresponds to that seen with continuous illumination. We tested the possibility that DBMIB was displacing the first stable electron acceptor, which has been shown to be a tightly bound ubiquinone (UQ) in R. rubrum. Chromatophores prepared from cells grown with ¹⁴C-p-hydroxybenzoic acid in their media provided a sample in which the benzoquinones were labelled specifically with ¹⁴C. These labelled chromatophores were first extracted with petroleum ether to remove the loosely bound ubiquinone pool and then were treated with DBMIB. DBMIB displaced about 1/2 of the remaining tightly-bound UQ present. The DBMIB inhibition was tested for reversibility by adding an excess of UQ to DBMIB-treated samples. In these cases, restoration to 80% could be achieved from samples which were only 20% active relative to the untreated samples. A similar inhibitory effect by DBMIB was also demonstrated in whole cells of Rhodospirillum rubrum, the G-9 mutant of Rhodospirillum rubrum, Rhodopseudomoms sphaeroides, Rhodopseudomonas capsulata, and Chromatium vinosum. The mechanism for inhibition is most consistent with displacement of, or interference with the first stable electron acceptor (ubiquinone) rather than by random quenching of excited states at the level of antenna bacteriochlorophyll.     

Absolute Konfiguration von Antheraxanthin, «cis-Antheraxantliirt» und der diastereomeren Mutatoxanthine

Absolute Configuration of Antheraxanthin, ‘cis-Aritheraxanthin’ and of the Stereoisomeric Mutatdxanthins The assignement of structure 2 to antheraxanthin (all-E)-(3 S, 5 R, 6 S, 3′ R)-5,6-epoxy-5,6-dihydro-β,β-carotene-3,3′-diol and of 1 to ‘cis-antheraxanthin’ (9Z)-(3 S, 5 R, 6 S, 3′ R)-5,6-epoxy-5,6-dihydro-β,β-carotene-3,3′-diol is based on chemical correlation with (3 R, 3′ R)-zeaxanthin and extensive ¹H-NMR. measurements at 400 MHz. ‘Semisynthetic antheraxanthin’ ( = ‘antheraxanthin B’) has structure 6 . For the first time the so-called ‘mutatoxanthin’, a known rearrangement product of either 1 or 2 , has been separated into pure and crystalline C(8)-epimers (epimer A of m.p. 213° and epimer B of m.p. 159°). Their structures were assigned by spectroscopical and chiroptical correlations with flavoxanthin and chrysanthemaxanthin. Epimer A is (3 S, 5 R, 8 S, 3′ R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol ( 4 ; = (8 S)mutatoxanthin) and epimer B is (3 S, 5 R, 8 R, 3′ R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol ( 3 ; = (8 R)-mutatoxanthin). The carotenoids 1 – 4 have a widespread occurrence in plants. We also describe their separation by HPLC. techniques. CD. spectra measured at room temperature and at ? 180° are presented for 1 – 4 and 6 . Antheraxanthin ( 2 ) and (9Z)-antheraxanthin ( 1 ) exhibit a typical conservative CD. The CD. Spectra also allow an easy differentiation of 6 from its epimer 2 . The isomeric (9Z)-antheraxanthin ( 1 ) shows the expected inversion of the CD. curve in the UV. range. The CD. spectra of the epimeric mutatoxanthins 3 and 4 (β end group) are dissimilar to those of flavoxanthin/chrysanthemaxanthin (ε end group). They allow an easy differentiation of the C (8)-epimers.     

Zur kenntnis von [O2]+[Mn2F9]−

[O₂]⁺[Mn₂F₉]^? has been prepared for the first time by reaction of MnO₂ or MnF_x (x = 2,3,4) with a mixture of fluorine and oxygen (P_F2/O₂ ≈ 300–3500 atm., t ≈ 350–550°C) either as a dark red powder or as ruby red needles or plates. From single crystal studies the space group is C2/c - C⁶_2h (No. 15) with a = 17.55₂, b = 8.37₃, c = 9.10₁ Å, β = 102.3°, Z = B (at ?150°C). The crystal structure has been refined to R = 0.053 (1619 unique reflections). From the structure determination [O₂]+[Mn₂F₉] has ‘mänder’ like bands of double chains of [MnF₆] octahedra, which are stacked up in layers parallel to (100) with O₂⁺-cations (d_0?0 = 1.10₀ Å) located between the layers. ν_O2 is at 1838 cm^?1 and the magnetic moment μ_eff = 5.63 B.M. is as expected for a ‘spin only’ case without spin-spin interaction.     

L'action de l'ammoniac sur l'hydroxyde de cobalt(II) et la stabilité des complexes en milieu aqueux

From the solubility of precipitated Co(OH)₂ (s) determined radiometrically as a function of pH and ammonia content of the heterogeneous systems, the formation constants have been obtained for the following mononuclear hydroxo-, ammine- and mixed hydroxo-ammine-complexes: Co(OH)₂, Co(OH)₃^?, Co(NH₃)₂²⁺, Co(NH₃)₃²⁺, Co(NH₃)₄²⁺ and Co(OH)₂ (NH₃)₂. The solubility of cobalt(II) hydroxide has also been calculated. The medium was 1M NaClO₄ and the temperature 25° C.     

Stabilité dans le méthanol et propriétés thermodynamiques de transfert des cryptates de certains cations de transition et de métaux lourds

Stability in Methanol and Thermodynamic Transfer Properties of the Cryptates of some Transition Cations and Heavy Metals The nature and stability of the macrocyclic and macrobicyclic complexes of Ag⁺, Cd²⁺, and Pb²⁺ (Mⁿ⁺) with 21, 22, 211, 221 and 222 in anhydrous methanol 0.05M in Et₄N⁺ClO^?₄, at 25° (see Scheme) have been determined by potentiometry and spectrophotometry. Binuclear complexes M₂L²ⁿ⁺ have been observed in all cases, besides the mononuclear MLⁿ⁺ complexes. The macrobicyclic 1:1 complexes MLⁿ⁺ exhibit an important ‘cryptate effect’ with Mⁿ⁺=Ag⁺, Pb²⁺ and Cd²⁺, but not with Cu²⁺ and Zn²⁺; their stability is in all cases maximum with 221. The applicability to our results of the recent extrathermodynamic hypothesis involving MLⁿ⁺ cryptates is examined.     

Complex Formation of 2, 6‐Bis‐(2′‐hydroxyphenyl)pyridine with AlIII,FeIII and CuII

Complex formation of 2, 6‐bis(2′‐hydroxyphenyl)pyridine (H₂Lⁱ) with Fe³⁺ and Cu²⁺ was investigated in a H₂O/DMSO medium (mole fraction x_DMSO = 0.2) by potentiometric and spectrophotometric methods. The pK_a values of [H₃Lⁱ]⁺ are 2.25, 10.51 and 14.0 (25 °C, 0.1 M KCl). The formation constants of [Fe^III(Lⁱ)]⁺ and [Cu^II(Lⁱ)] (25 °C, 0.1 M KCl) are log β₁ = 21.5 for Fe³⁺ and log β₁ = 18.5 for Cu²⁺. The crystal structures of [Al(Lⁱ)₂Na(EtOH)₃], [Fe(Lⁱ)₂Na(EtOH)₃], and [Cu(Lⁱ)(py)]₂ were investigated by single‐crystal X‐ray diffraction analyses. The Fe^III and the Al^III compound are isotypic and crystallize in the monoclinic space group P2₁/n. Al‐compound (215 K): a = 12.599(3) Å, b = 16.653(3) Å, c = 17.525(4) Å, β = 100.27(3)°, Z = 4 for C₄₀H₄₀AlN₂NaO₇; Fe‐compound (293 K): a = 12.753(3) Å, b = 16.715(3) Å, c = 17.493(3) Å, β = 99.68(3)°, Z = 4 for C₄₀H₄₀FeN₂NaO₇. Both compounds contain a homoleptic, anionic bis‐complex [M(Lⁱ)₂]^‐ of approximate D₂ symmetry. The Cu compound crystallized as an uncharged, dinuclear and centrosymmetric [Cu(Lⁱ)(py)]₂ complex in the monoclinic space group P2₁/n with (293 K) a = 13.386(3) Å, b = 9.368(2) Å, c = 14.656(3) Å, β = 100.65(3)°, Z = 2 for C₄₄H₃₂Cu₂N₄O₄. The structural properties and in particular the possible influence of the ligand geometry on the stability of the metal complexes is discussed.     

Protonation and Hydrogen Atom Abstraction Reactions in the Synthesis of the [HP7M(CO)3]2– Ions (M = Cr,W)

Ethylenediamine (en) solutions of [P₇M(CO)₃]^3– (M = Cr, W) react with weak acids to give [HP₇M(CO)₃]^2– ions where M = Cr ( 4 a ) and W ( 4 b ) in high yields. Competition studies with known acids revealed a pK_a range for 4 b in DMSO of 17.9 to 22.6. The [P₇M(CO)₃]^3– complexes also react with one-half equivalent of I₂ to give 4 through an oxidation/hydrogen atom abstraction process. Labeling studies show that the abstracted hydrogen originates from the [K(2,2,2-crypt)]⁺ ions or from the solvent (DMSO-d₆) in the absence of [K(2,2,2-crypt)]⁺ or other good hydrogen atom donors. In the solid state, the ions have no crystallographic symmetry but in solution they show virtual C_s symmetry (³¹P NMR spectroscopy) due to an intramolecular wagging process. Crystallographic data for [K(2,2,2-crypt)]₂[HP₇W(CO)₃]: triclinic, P 1, a = 10.9709(8) Å, b = 13.9116(10) Å, c = 19.6400(14) Å, α = 92.435(6)°, β = 93.856(6)°, γ = 108.413(6)°, V = 2831.2(4) ų, Z = 2, R(F) = 7.65%, R(wF²) = 14.17% for all 7400 reflections. For [K(2,2,2-crypt)]₂[HP₇Cr(CO)₃]: triclinic, P 1, a = 12.000(3) Å, b = 14.795(3) Å, c = 17.421(4) Å, α = 93.01(2)°, β = 93.79(2)°, γ = 110.72(2)°, V = 2877(2) ų, Z = 2.     

Synthese von Glycerylätherphosphatiden 1. Mitteilung Herstellung von 1-O-Octadecyl-2-O-acetyl-sn-glyceryl-3-phosphorylcholin1 (‘Platelet Activating Factor’), des Enantiomeren sowie einiger analoger Verbindungen

Synthesis of Glyceryletherphosphatides, 1st Communication, Preparation of 1-O-Octadecyl-2-O-acetyl-sn-glyceryl-3-phosphorylcholine (‘Platelet Activating Factor’), of its Enantiomer and of Some Analogous Compounds Several synthetic sequences for the preparation of ‘Platelet Activating Factor’ ( 1a ), for the corresponding enantiomeric compound ( 1′a ) as well as for the ‘Lyso-compounds’ ( 1b and 1′b ) are described. The use of glycerolacetonide 2′a (from D-Mannitol) for the preparation of 1′a and la is presented together with the synthesis of some analogues of 1′a and 1a . Structural assignment and optical purity of the compounds prepared are confirmed.     

Long‐range 19F–15N heteronuclear shift correlation: examination of J‐modulations associated with broad range accordion excitation

The first demonstrated example of ¹⁹F–¹⁵N long‐range heteronuclear shift correlation spectroscopy at natural abundance is reported. Because of the very large variation in the size of ²J(N,F) vs ³J(N,F) long‐range heteronuclear couplings, the utilization of one of the new accordion‐optimized long‐range heteronuclear shift correlations experiments is essential if all possible correlations are to be observed in a single experiment. A modified IMPEACH‐MBC pulse sequence was used in conjunction with an optimization range from 4 to 50 Hz to demonstrate the technique using a mixture of 2‐ and 3‐fluoropyridine, which had ²J(N,F) and ³J(N,F) long‐range couplings of ?52 and 3.6 Hz, respectively. Because of the size of the ²J(N,F) long‐range coupling constant, a J‐modulation of the long‐range correlation response is observed in the spectrum resulting in a ‘doublet’ in F₁ due to amplitude modulation. The size of the ‘doublet’ is shown to be a function of the parameter selection (t_1max,T_max,T_min and spectral width in F₁). This behavior is similar to F₁ ‘skew’ associated with long‐range correlation responses in ACCORD‐HMBC spectra which has been analyzed in detail previously. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthese und Kristallstruktur des Fluorid‐ino‐Oxosilicats Cs2YFSi4O10

Synthesis and Crystal Structure of the Fluoride ino‐Oxosilicate Cs₂YFSi₄O₁₀ The novel fluoride oxosilicate Cs₂YFSi₄O₁₀ could be synthesized by the reaction of Y₂O₃, YF₃ and SiO₂ in the stoichiometric ratio 2 : 5 : 3 with an excess of CsF as fluxing agent in gastight sealed platinum ampoules within seventeen days at 700 °C. Single crystals of Cs₂YFSi₄O₁₀ appear as colourless, transparent and water‐resistant needles. The characteristic building unit of Cs₂YFSi₄O₁₀ (orthorhombic, Pnma (no. 62), a = 2239.75(9), b = 884.52(4), c = 1198.61(5) pm; Z = 8) comprises infinite tubular chains of vertex‐condensed [SiO₄]^4? tetrahedra along [010] consisting of eight‐membered half‐open cube shaped silicate cages. The four crystallographically different Si⁴⁺ cations all reside in general sites 8d with Si–O distances from 157 to 165 pm. Because of the rigid structure of this oxosilicate chain the bridging Si–O–Si angles vary extremely between 128 and 167°. The crystallographically unique Y³⁺ cation (in general site 8d as well) is surrounded by four O^2? and two F^? anions (d(Y–O) = 221–225 pm, d(Y–F) = 222 pm). These slightly distorted trans‐[YO₄F₂]^7? octahedra are linked via both apical F^? anions by vertex‐sharing to infinite chains along [010] (?(Y–F–Y) = 169°, ?(F–Y–F) = 177°). Each of these chains connects via terminal O^2? anions to three neighbouring oxosilicate chains to build up a corner‐shared, three‐dimensional framework. The resulting hexagonal and octagonal channels along [010] are occupied by the four crystallographically different Cs⁺ cations being ten‐, twelve‐, thirteen‐ and fourteenfold coordinated by O^2? and F^? anions (viz.[(Cs1)O₁₀]^19?, [(Cs2)O₁₀F₂]^21?, [(Cs3)O₁₂F]^24?, and [(Cs4)O₁₂F₂]^25? with d(Cs–O) = 309–390 pm and d(Cs–F) = 360–371 pm, respectively).     

Hydrothermal Preparation,Crystal Structure and Properties of {[ZnTCPP(EtOH)][Zn(en)]2}n(EtOH)2n with a Novel Two‐Dimensional (2‐D) Motif

A novel zinc porphyrin, {[ZnTCPP(EtOH)][Zn(en)]₂}_n(EtOH)_2n ( 1 ) (TCPP=meso‐tetra(4‐carboxyphenyl)‐porphyrin; EtOH=ethanol; en=ethylenediamine) was obtained via a hydrothermal reaction and characterized by single‐crystal X‐ray diffraction. Complex 1 crystallizes in the space group C2/c of the monoclinic system with eight formula units in a cell: a=32.465(4) Å, b=10.527(3) Å, c=31.845(3) Å, β=95.524(6) °, V=10832(4) ų, C₅₈H₅₇N₈O₁₁Zn₃, M_r=1238.23, D_c=1.518 g/cm³, S=1.005, µ(Mo Kα) =1.388 mm^?1, F(000) =5112, R=0.0650 and wR=0.1574. Complex 1 features a novel 2‐D layered motif. The spectral data of UV‐vis, FT‐IR and fluorescence are reported.     

Darstellung und Eigenschaften von Tetra(n-butyl)ammonium-cis-trifluorophthalocyaninato(2–)zirconat(IV) und -hafnat(IV); Kristallstruktur von (nBu4N)cis[Hf(F)3pc2–]

Preparation and Properties of Tetra(n-butyl)ammonium cis -Trifluorophthalocyaninato(2–)zirconate(IV) and -hafnate(IV); Crystal Structure of (ⁿBu₄N) ^cis [Hf(F)₃pc^2–] cis-Dichlorophthalocyaninato(2–)metal(IV) of zirconium and hafnium reacts with excess tetra(n-butyl)-ammoniumfluoride trihydrate to yield tetra(n-butyl)-ammonium cis-trifluorophthalocyaninato(2–)metalate(IV), (ⁿBu₄N)^cis[M(F)₃pc^2–] (M = Zr, Hf). (ⁿBu₄N)^cis[Hf(F)₃pc^2–] crystallizes in the monoclinic space group P2₁/n (# 14) with cell parameters a = 13.517(1) Å, b = 13.856(1) Å, c = 23.384(2) Å, α = 92.67(1)°, Z = 4. The Hf atom is in a ”︁square base-trigonal cap”︁”︁ polyhedron, coordinating three fluorine atoms and four isoindole nitrogen atoms (N_iso). The Hf atom is sandwiched between the (N_iso)₄ and F₃ planes (d(Hf–Ct_N) = 1.218(3) Å; d(Hf–Ct_F) = 1.229(3) Å; Ct_N/F: centre of the (N_iso)₄, respectively F₃ plane). The average Hf–N_iso and Hf–F distances are 2.298 and 1.964 Å, respectively, the average F–Hf–F angle is 84.9°. The pc^2– ligand is concavely distorted. The optical spectra show the typical metal independent π-π* transitions of the pc^2– ligand at c. 14700 and 29000 cm^–1. In the FIR/MIR spectra vibrations of the MF₃ skeleton are detected at 545, 489, 274 cm^–1 (M = Zr) and 536, 484, 263 cm^–1 (M = Hf), respectively.