Structural chemistry of lanthanidedicyclopentadienidehalides. Part 1. Two modifications of gadoliniumdicyclopentadienidebromide, [Gd(C5H5)2Br]2 and 1∞[Gd(C5H5)2Br]

The crystal structures of two modifications of gadoliniumdicyclopentadienidebromide, [Gd(C₅H₅)₂Br]₂ (I) and ¹_∞[Gd(C₅H₅)₂Br] (II) have been determined from X-ray diffraction data. I crystallizes in the [Sc(C₅H₅)₂Cl]₂-type structure, space group P2₁/c, with a=14.110(3), b=16.488(3), c= 13.765(3) Å, β=93.25(2)°, V=3197(2) ų, and D_c= 2.289 g cm⁻³ for Z=6 molecules. II crystallizes in space group P2₁/c with a=5.946(7), b=8.447(5), c=20.239(9) Å, β=90.11(4)°, V=1020(2) ų, D_c=2.392 g cm⁻³ for Z=4 formula units. The structures have been refined by full matrix least-squares techniques to conventional R factors of 0.034 for 3014 (I) and 1964 (II) reflections (with I>2σ(I)). I consists of dimers with two bromine bridges (mean GdBr 2.872 Å). II has a double chain structure with alternating juxtaposition of gadolinium and bromine atoms (GdBr 2.912 Å (once) and 3.133 Å (twice)). The arrangement of the C₅H₅ groups with regard to the metal η⁵ fashion) is nearly identical in I and II (mean GdC 2.63(1) Å (I) and 2.62(1) Å (II)). Single crystals of I and II are obtained by sublimation at different temperatures. The formation of both modifications is discussed as to its dependence on the state of the gaseous phase equilibrium [Gd(C₅H₅)₂Br]₂ ⇄ 2Gd(C₅H₅)₂Br. Obviously, I crystallizes from gaseous phase dimers while II forms from the monomers.     

中国人红细胞葡糖6-磷酸脱氢酶变异型的研究 Ⅵ.Gd(-) Dhon型和Gd(-) Haad Yai型

红细胞葡糖6-磷酸脱氢酶(G6PD)缺乏症经证明是引起多种溶血性贫血的原因。中国人中已报告了17种变异型。其中包括1980年Panich等在泰国华侨中发现的Dhon型和Haad Yai型。我们近年来在广东居民中亦发     

Syntheses of (±)-Epoformin (Desoxyepoxydon) and (±)-Epiepoformin (Desoxyepiepoxydon)

Boron is an essential nutrient for plants, but it is toxic in excess. Transgenic rice plants expressing an Arabidopsis thaliana borate efflux transporter gene, AtBOR4, at a low level exhibited increased tolerance to excess boron. Those lines with high levels of expression exhibited reduced growth. These findings suggest a potential of the borate transporter BOR4 for the generation of high-boron tolerant rice.     

Synthesis of (S)-(—)-Vertinolide

(S)-(?)-Vertinolide 1 was synthesized via the tetronic acid derivative 6 from (S)-(?)-tetrahydro-2-methyl-5-oxo-2-furancarboxylic acid 3. (±)-Vertinolide was also synthesized from (±)-3.     

Synthesis of (±)-licarin-B

The synthesis of (±)-licarin-B, a neolignan of Licaria aritu Ducke (Lauraceae), was achieved by pyrolysis of 3-hydroxy-3-piperonyl-1-propyl-2-methoxy-4-(E)-propenylphenyl ethers.     

Synthesis of (–)-Muricatacin

The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.     

Synthesis of (±)-Homosarkomycin and (±)-Rosaprostol

(±)-Homosarkomycin (2) and (±)-rosaprostol (3) were synthesized from (±)-methyl 2-oxo-bicyclo[3.1.0]hexane-1-carboxylate (1) by using the nucleophilic ring opening reaction on the double-activated cyclopropane ring as the key step.     

Synthesis of (±)-Lamprolobine and (±)-Epilamprolobine

(±)-Lamprolobine, the (+)-enatiomer of which was isolated from the leaves of Lamprolobium fruticosum, and (±)-epilamprolobine were synthesized from δ-valerolactam.     

Structural diversity of neutral bis-(β-iminoaldehyde) complexes of nickel(II)

Series of Ni^II and Cu^II complexes with dianionic [N₂O₂] ligands were synthesized and characterised applying spectroscopic and X-ray diffraction techniques. The ligands were obtained by 1:2 condensation of ethylene- and propylenediamine with malonic aldehyde derivatives (R² = H, R¹ = H or OCH₃). Although the molecular formulae of the complexes are quite similar, the X-ray investigations have proved a significant structural diversity in the solid state. Among others, we found some simple nearly planar molecules stacked in the crystal lattice with electron density of six-membered rings delocalised over the chelate rings as well as some very complex polymeric or nickel acetate bridged trinuclear complexes. The coordination of the nickel ion by surrounding oxygen and nitrogen atoms is square-planar in the simplest case and octahedral in the most complex one. Small topological differences in similar molecules generate completely different crystal structures.From magnetic studies, a small, negative value of J obtained confirms the occurrence of weak antiferromagnetic interactions between the Ni^II ions in polymeric chain of the propylenediamine dialdehyde substituted derivative.     

Synthesis of (±)-Xanthoxins

The enzymatic properties of P2-2 enzyme were determined by using cells of M. radiodurans. The enzyme was: most active at 60°C incubation temperature, stable at 40°C in neutral buffer, and inactivated by heating at 80°C for 15min. Maximal lytic activity occurred at pH 8.5 in Tris-HCl buffer. The range of enzyme stability was between pH 5.5 and 8. Bivalent metal ions, p-chloromercuribenzoate and monoiodo acetate inhibited lytic activity. The molecular weight was estimated to be 16,000 daltons by gel filtration on Sephadex G-75. The enzymatic digestion of peptidoglycans from the cell walls of M. radiodurans and M. lysodeikticus liberated free amino groups, but neither reducing groups nor N-acetylhexosamine, indicating that the enzyme was an endopeptidase. From analysis of the N-terminal amino acids of the digests, it is suggested that the P2-2 enzyme cleaves the peptide bond at the carboxyl group of D-alanine in peptidoglycan.     

Synthesis of (±)-Hydroxytremetone

(±)Hydroxytremetone (III) has been synthesized from 2-(α-hydoxyisopropyl)-6-hydroxycoumaran (V b) via its O-acetate V c by dehydration with phosphorus tribromide in pyridine solution, followed by acylation with a mixture of trifluoroacetic anhydride and acetic acid. Isohydroxytremetone (IX b) was also synthesized.     

Biological function of modified nucleotides T_(54) and ψ_(55) of yeast tRNA~(Ala)

The 3' half molecule of yeast tRNAAla (nucleotides 36-75) was hybridized with a DNA fragment (5'GGAATCGAACC 3') and the hybrid was then digested with E. coli RNase H (from Boehringer). The enzyme can specifically cleave the 3' half molecule at the 3' side of nucleotide ψ55, thus a fragment C36-ψ55 was prepared. The 3'-terminal T or Tψ of this fragment was removed by one or two cycles of periodate oxidation and $-elimination. The products were fragments C36-T54 and C36-G53. Three yeast tRNAAla fragments C56-A76, U55-A76 (with ψ55 replaced by U), U54-A76 (with T54ψ55 replaced by UU) were synthesized and ligated with three prepared fragments (C36-ψ55 C36-T54 and C36-G53) respectively by T4 RNA ligase. The products were further ligated with the 5' half molecule (nu-cleotides 1-35). Using this method, one reconstituted yeast tRNAAla (tRNAr) and two yeast tRNAAla analogs: (i) tRNAa with U55 instead of ψ55; (ii) tRNAb with U54U55 instead of T54ψ55 were synthesized. The charging and incorporation activi     

Structure of Poly (dT)·Poly (dA)·Poly (dT)

Abstract

The molecular structure of poly (dT)·poly (dA)·poly (dT) has been determined and refined using the continuous x-ray intensity data on layer lines in the diffraction pattern obtained from an oriented fiber of the DNA. The final R-value for the preferred structure is 0.29 significantly lower than that for plausible alternatives. The molecule forms a 12-fold right- handed triple-helix of pitch 38.4 Å and each base triplet is stabilized by a set of four Crick-Watson-Hoogsteen hydrogen bonds. The deoxyribose rings in all the three strands have C2′-endo conformations. The grooveless cylindrical shape of the triple-helix is consistent with the lack of lateral organization in the fiber.     

Asymmetric synthesis of (S)-α-(octyl)glycine via alkylation of Ni(II) complex of chiral glycine Schiff base

Over last decade, the use of Ni(II) complexes, derived from of glycine Schiff bases with chiral tridentate ligands, has emerge as a leading methodology for preparation of structurally diverse Tailor-Made Amino Acids, the key structural units in modern medicinal chemistry, and drug design. Here, we report asymmetric synthesis of derivatives of (S)-α-(octyl)glycine ((S)-2-aminodecanoic acid) and its N-Fmoc derivative via alkylation of chiral nucleophilic glycine equivalent with n-octyl bromide. Under the optimized conditions, the alkylation proceeds with excellent yield (98.1%) and diastereoselectivity (98.8% de). The observed stereochemical outcome and convenient reaction conditions bode well for application of this method for large-scale asymmetric synthesis of (S)-2-aminodecanoic acid and its derivatives.     

Synthesis of (±)-Tubaic Acid

An alternative synthesis of (±)-tubaic acid (I), a key intermediate compound of rotenone synthesis, has been accomplished by the Wittig reaction.     

Dynamic aggregation of the mid-sized gadolinium complex {Ph4[Gd(DTTA)(H2O)2]− 3}

A compound binding three Gd³⁺ ions, {Ph₄[Gd(DTTA)(H₂O)₂]^? ₃} (where H₅DTTA is diethylenetriaminetetraacetic acid), has been synthesized around a hydrophobic center made up of four phenyl rings. In aqueous solution the molecules start to self-aggregate at concentrations well below 1 mM as shown by the increase of rotational correlation times and by the decrease of the translational self-diffusion constant. NMR spectra recorded in aqueous solution of the diamagnetic analogue {Ph₄[Y(DTTA)(H₂O)₂]^? ₃} show that the aggregation is dynamic and due to intermolecular π-stacking interactions between the hydrophobic aromatic centers. From estimations of effective radii, it can be concluded that the aggregates are composed of two to three monomers. The paramagnetic {Ph₄[Gd(DTTA)(H₂O)₂]^? ₃} exhibits concentration-dependent ¹H NMR relaxivities with high values of approximately 50 mM^?1 s^?1 (30 MHz, 25 °C) at gadolinium concentrations above 20 mM. A combined analysis of ¹H NMR dispersion profiles measured at different concentrations of the compound and ¹⁷O NMR data measured at various temperatures was performed using different theoretical approaches. The fitted parameters showed that the increase in relaxivity with increasing concentration of the compound is due to slower global rotational motion and an increase of the Lipari–Szabo order parameter S ².     

Redescription of Skrjabinodon medinae (García-Calvente, 1948) (Nematoda: Pharyngodonidae) from the cloaca of Podarcis pityusensis (Bosca, 1883) (Sauria: Lacertidae) of the Balearic Islands (Spain)

Pharyngodon medinae García-Calvente, 1948 (Nematoda: Pharyngodonidae) is redescribed from Podarcis pityusensis (Bosca, 1883) (Sauria: Lacertidae) of the Balearic Islands (Spain) and confirmed as a member of the genus Skrjabinodon Inglis, 1968. A systematic review of S. medinae and closely related species is also given. Parathelandros canariensis is referred to Skrjabinodon as a new combination and Parathelandros Magzoub et al., 1980 is dismissed as a junior homonym of Parathelandros Baylis, 1930.     

Optical Resolution of (±)-Metyrosine

A lipase gene (lip) and its activator gene (act) on a 2.9 kb BglII-EcoRI fragment from Pseudomonas sp. KWI-56 were cloned in Escherichia coli using pUC19 as a vector plasmid. From the sequencing results, the open reading frames of the lip and the act were found to contain 1092 and 1032 nucleotides, respectively. The act existed downstream of the lip with the same orientation. When the lip was expressed in E. coli using the lac promoter on the pUC plasmid vector, the lipase activity of E. coli carrying both the lip and the act was 200-fold greater than that carrying only the lip. This result suggested the act was important in the expression of the lip in E. coli.     

f-element/crown ether complexes. 6. Interaction of hydrated lanthanide chlorides with 15-crown-5: Crystallization and structures of [M(OH2)8]Cl3·(15-crown-5) (M = Gd,Lu)

The interaction of hydrated chloride salts of Gd³⁺ and Lu³⁺ with 15-crown-5 in a 1:3 mixture of CH₃OH:CH₃CN produces crystalline [M(OH₂)₈]Cl₃· (15-crown-5) (M = Gd, Lu). The crystal and molecular structures of both complexes have been determined by single crystal X-ray diffraction. Both are isostructural with previously determined Y analog and crystallize in the monoclinic space group P2₁/n with Z = 4. Lattice parameters are a = 9.247(4), b = 17.312(5), c = 15.191(6) Å, β = 92.19(3)°, D_calc = 1.72 g cm⁻³ for M = Gd and a = 9.150(1), b = 17.171(1), c = 15.217(1) Å, β = 92.64(1)°, D_calc = 1.80 g cm⁻³ for M = Lu. Each complex was refined by least-squares to final conventional R values of 0.052 (M = Gd, 2932 observed [F_o⩾5σ(F_o) reflections) and 0.036 (M = Lu, 3313 observed reflections). The octaaquo M(III) ions exist as a distorted dodecahedron with average MOH₂ separations of 2.41(4) Å (M = Gd) and 2.35(4) Å (M = Lu). The crown ether molecule is hydrogen bonded to metal coordinated water molecules to form polymeric chains along b. The remaining water molecule hydrogen atoms participate in hydrogen bonds with the chloride ions essentially in the ac plane. Two resolvable disordered crown ether conformations are observed with occupancies of 60%/40% (M = Gd) and 75%/25% (M = Lu).