Boron heterocycles derived from 2-guanidinobenzimidazole

The syntheses and structure determinations of a series of boron heterocycles derived from 2-guanidinobenzimidazole 1 are reported. Structures of new compounds, 2-guanidino-1-methyl-benzimidazole 2, diphenyl-(2-guanidinobenzimidazole-N,N′)-borate 3, diphenyl-(2-guanidino-1-methyl-benzimidazole-N,N′)borate 4, hydroxy-phenyl-(2-guanidino-benzimidazole-N,N′)borate 5, hydroxy-phenyl-(2-guanidino-1-methyl-benzimidazole-N,N′)borate 6,methoxy-phenyl-(2-guanidinobenzimidazole-N,N′)borate 7, isopropoxy-phenyl-(2-guanidinobenzimidazole-N,N′)borate 8, acetoxy-phenyl-(2-guanidinobenzimidazole-N,N′)borate 9, methoxy-phenyl-(2-guanidino-1-methyl-benzimidazole-N,N′)borate 10, dihy-droxy-(2-guanidino-1-methyl-benzimidazole-N,N′)borate 16, difluoro-(2-guanidinobenzimidazole-N,N′)borate, 17, dihydroxy-(2-guanidino-1-benzimidazole-N,N′)borate potassium salt 19, diphenyl-(2-guanidinium-10H-benzimidazole-N,N′)borate hydro-chloride 20, methoxy-phenyl-(2-guanidinobenzimidazole-N,N′)borate hydrochloride 21, and N10-borane-(diphenyl-2-guanidinobenzimidazole-N,N′)borate 22, were determined based on ¹H, ¹³C, ¹⁵N, and ¹¹B spectroscopy. The X-ray diffraction structures of 3–7, 19, and 20 were obtained. The formation of N3-borane adducts 11 and 12 derived from compounds 1 and 2, respectively, and the dihydride-(2-guanidinobenzimidazole-N,N′)borate 13 and dihydride-(2-guanidino-1-methyl-benzimidazole-N,N′)borate 14 were observed by ¹¹B NMR. The results show that 2-guanidinobenzimidazole gives stable borate heterocycles with a delocalized π electronic system. A dynamic exchange of N–H protons was observed with preferred protonation at N-12. The new heterocycles are protonated at N-10 by acidic substances to give pyridinium-type heterocycles or can lose a proton to give iminium salts. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:399–409, 1998     

Pentopyranosyl Oligonucleotide Systems,Communication No. 10 , The α‐L‐Lyxopyranosyl‐(4′→2′)‐oligonucleotide System

To determine whether the remarkable chemical properties of the pyranosyl isomer of RNA as an informational Watson‐Crick base‐pairing system are unique to the pentopyranosyl‐(4′→2′)‐oligonucleotide isomer derived from the RNA‐building block D ‐ribose, studies on the entire family of diastereoisomeric pyranosyl‐(4′→2′)‐oligonucleotide systems deriving from D ‐ribose, L ‐lyxose, D ‐xylose, and L ‐arabinose were carried out. The result of these extended studies is unambiguous: not only pyranosyl‐RNA, but all members of the pentopyranosyl‐(4′→2′)‐oligonucleotide family are highly efficient Watson‐Crick base‐pairing systems. Their synthesis and pairing properties will be described in a series of publications in this journal. The present paper describes the α‐L ‐lyxopyranosyl‐(4′→2′)‐system.     

Synthesis and properties of adenylate trimers A2′p5′A2′p5′A,A2′p5′A3′p5′A and A3′p5′A2′p5′A

Triadenylates with (2′-5′)(2′-5′) and mixed (2′-5′)(3′-5′) and (3′-5′)(2′-5′) linkages respectively were synthesized via the phosphotriester approach followed by deblocking of the fully protected intermediates. The isomeric trimers were characterized by NMR- and CD-spectra and show very similar hypochromicity effects.     

拉伸取向尼龙1010样品的抗张回复

研究了拉伸取向尼龙 10 10的抗张回复现象 .残存应变ε′表征了由链滑移而产生的永久形变 ,回复应变(ε -ε′)表征了键角变化和链段取向产生的形变 .当拉伸温度T=18℃ (T 相似文献   

Semisynthesis of 3′(2′)‐O‐(Aminoacyl)‐tRNA Derivatives as Ribosomal Substrate

An efficient synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated pCpA derivatives is described, which could lead to the production of (aminoacyl)‐tRNAs following T4 RNA ligase mediated ligation. The tetrahydrofuranyl (thf) group was used as a permanent protective group for the 2′‐OH of the cytidine moiety which can be removed during the purification of the 3′(2′)‐O‐aminoacylated‐pCpA. This approach allowed for a general synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated oligonucleotides. The fully protected pCpA 14 was synthesized by phosphoramidite chemistry and treated with NH₃ solution to remove the 2‐cyanoethyl and benzoyl groups (→ 15 ; Schemes 1 and 2). The 2′‐O‐thf‐protected‐pCpA 15 was coupled with α‐amino acid cyanomethyl esters, and the products 20a – c were deprotected and purified with AcOH buffer to afford 3′(2′)‐O‐aminoacylated pCpA 21a – c in high yields. The 3′(2′)‐O‐aminoacylated pCpA were efficiently ligated with tRNA(? CA) to yield (aminoacyl)‐tRNA which was an active substrate for the ribosome.     

Synthese du trimere de la β-D-xylofurannosyl-9 adenine a liaisons internucleotidiques 2′→5′.

The trimeric xylo-adenylyl(2′→5′)-xylo-adenylyl-(2′→5′)-xyloadenosine $\text{1}$ was synthesized by the modified phosphotriester approach, followed by deblocking the fully, protected intermediates.     

Recherches dans la serie des metallocenes : XXXI. Synthese de di-σ-aryloxy di-π-cyclopentadienyl titanes dissymetriques et selectivite du deplacement des ligands

Three methods of obtaining asymmetric diaryloxy complexes of titanium (h⁵-Cp)(h⁵-Cp′)Ti(OAr)(OAr′) are proposed.Each of these methods leads to secondary products, selective substitution of the ligand (OAr) or (OAr′) by chlorine atom occurs by the action of hydrochloric acid in C₆H₆ solution.     

Nucleotides. Part XXXVI. Syntheses and biological characterization of phosphorothioate analogues of (3′–5′)adenylate trimer

The four protected diastereoisomcrs 7a / 7b and 8a / 8b P-thioadenylyl-(3′–5′)-P-thioadenylyI-(3′–5′)-adenosine were synthesized, separated, and deblocked to the free oligonucleotides (Scheme). Biochemical characterization of these (3′–5′)phosphorothioate analogues of adenyiate trimer indicate that these compounds, and the corresponding 5′-monophosphates, neither bind to nor activate RNase L, and are considered to be valuable control compounds in screening experiments.     

Synthesis of a novel [10]ferrocenophanedioxime with bridge heteroatoms and of its nickel(II) complex

1,10-Dithia-4,7-diaza-5,6-bis(hydroxyimino)[10](1,1′)ferrocenophane has been prepared by the reaction of S,S′-bis(aminoethyl)(1,1′)dithiaferrocene with anti-di-chloroglyoxime. The nickel(II) complex of the new ligand has been isolated.     

Hydroacridines: Part 23. 1H and 13C NMR spectra of sym‐octahydroacridine,its 9‐(3‐pyridyl) and 9‐(4‐pyridyl) derivatives and the corresponding N(10)‐oxides. An experimental approach to the diamagnetic anisotropy of the pyridine nucleus

The complete ¹H NMR chemical shift assignments of 1,2,3,4,5,6,7,8‐octahydroacridine ( 1 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(3‐pyridyl)acridine ( 2 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(4‐pyridyl)acridine ( 3 ) and the corresponding N(10)‐oxides 1a , 2a and 3a , respectively, were achieved on the basis of 400 MHz ¹H NMR spectra and proton–proton decoupling, HMQC and NOEDIFF experiments. The spectral data for the above compounds provided the first experimental evidence of the difference in the anisotropy effect of the two non‐symmetrical moieties of the pyridine nucleus, and allowed us to ascertain that the shielding effect of the moiety defined by the C(2′)—N—C(6′) atoms is weaker than that of the C(3′)—C(4′)—C(5′) moiety. The ¹³C NMR spectra of 1 – 3 and 1a – 3a and the effect of N(10)‐oxidation on the ¹³C NMR chemical shifts are also discussed. The N‐oxidation of 2 and 3 with m‐chloroperbenzoic acid occurred regiospecifically, affording the N(10)‐oxides 2a and 3a free of N(1′)‐oxide isomers. Copyright © 2002 John Wiley & Sons, Ltd.     

(O,O′)-Diorganodithiophosphatophenyltellur(II)- und Tris[(O,O′)-diorganodithiophosphato]phenyltellur(IV)-Verbindungen; Kristallstruktur von Tris[(O,O′)-diphenyldithiophosphato]phenyltellur(IV)

(O,O′)-Diorganodithiophosphatophenyltellurium(II)- and Tris[(O,O′)-diorganodithiophosphato]phenyltellurium(IV) Compounds; Crystal Structure of Tris[(O,O′)-diphenyldithiophosphato]phenyltellur(IV) The title compounds are available by reaction of trichlorophenyltellurium(IV) respectively iodophenyltellurium(II) with the sodium or ammonium salts of (O,O′)-diorganodithiophosphorus acids in various solvents. The resulting tellurium(IV) compounds have a pronounced tendency towards reductive elimination of bis[(O,O′)-diorganothiophosphoryl]disulfanes [S₂P(OR)₂]₂ in solution. In contrast, the tellurium(II) compounds are stable, although they are disintegrated to diphenylditellane and [S₂P(OR)₂]₂ on prolonged standing in chlorinated hydrocarbons. Crystals of tris[(O,O′)-diphenyldithiophosphato]phenyltellurium(IV) are monoclinic (space group P2₁/c) with the cell constants: a = 1 039.2(1), b = 1 037.9(3), c = 4 205.0(1) pm, β = 95.273(1)°, V = 4 516.42(9)X10⁶ pm³, Z = 4. The compound appears to be monomeric in the solid state forming a distorted pentagonal bipyramid. The stereochemical influence of the lone pair of electrons causes the axial (i. e. C1? Te? S4) angle to be 156.6(1)° rather than the theoretical 180°.     

Spektroskopische und strukturelle Charakterisierung von Tris(2, 6‐di‐t‐butyl‐phenolato)lanthanid(III) (Ln(OAr′)3; Ln = Pr,Nd) sowie parametrische Analyse des Kristallfeld‐Aufspaltungsmusters von Nd(OAr′)3

Electronic Structures of Highly Symmetrical Compounds of f Elements. 37 [1] Spectroscopic and Structural Characterization of Tris(2, 6‐di‐t‐butyl‐phenolato)lanthanide(III) (Ln(OAr′)₃; Ln = Pr, Nd), and Parametric Analysis of the Crystal Field Splitting Pattern of Nd(OAr′)₃ Pr(OAr′)₃ and Nd(OAr′)₃ crystallize (at approximately 150 K and 200 K, respectively) in the monoclinic space group P2₁ with four molecules in the unit cell. If one considers only the directly coordinating oxygen atoms, the effective crystal field is of C_3v symmetry. The signals in the optical spectra of Pr(OAr′)₃ are broad using either solutions or solids, even at ca. 80‐90 K, thus they are not suitable for interpretation purposes. Nd(OAr′)_3, however, exhibits sharp absorption bands at room and low temperatures, which are assigned in analogy to the previously identified absorption transitions of Nd[N(SiMe₃)₂]₃ based on optical polarization measurements. The thus derived crystal field splitting pattern is simulated by fitting the free parameters of a phenomenological Hamiltonian, achieving a reduced r.m.s. deviation of 26.4 cm^—1 for 64 assignments. The parameters used allow the estimation of the ligand field strength associated with the (OAr′)^— ligand, the insertion of this ligand into empirical nephelauxetic and relativistic nephelauxetic series, and the setup of experimentally‐based non‐relativistic and relativistic molecular orbital schemes in the f range.     

Synthesis of a protein biosynthesis inhibitor, 5′-tri-phosphoryladenylyl-(2′-5′)-adenosine

A protein biosynthesis inhibitor, 5′-triphosphoryladenylyl-(2′-5′)-adenylyl-(2′-5′)-adenosine was synthesized by polymerization of N⁶-benzoyl-3′-O-(o-nitrobenzyl)adenosine 5′-phosphate follwed by reaction with pyrophosphate using 1,1′-carbonyldiimidazole.     

Azahelicenes from the Oxidative Photocyclization of Boron Hydroxamate Complexes

Aromatic hydroxamic acids (Ar–CO–NOH–Ar′) were used as bidentate chelating ligands to generate the corresponding boron hydroxamate complexes, which were subsequently transformed into nitrogen‐containing helicenes (azahelicenes) using an oxidative photocyclization method that is frequently used for stilbene‐type (Ar–CH=CH–Ar′) precursors of carbohelicenes. The nitrogen atom of the hydroxamate linker was thus directly embedded into the helicene core without using nitrogen‐containing aromatic rings in the stilbene‐type precursors. In a batch photoreaction, aza[4]helicenes were readily and efficiently prepared, but aza[6]helicenes underwent severe decomposition upon irradiation. Alternatively, a continuous flow photoreactor was employed to furnish an amide‐type aza[6]helicene.     

Precise Synthesis of New Triblock Co- and Terpolymers by a Methodology Combining Living Anionic Polymers with a Specially Designed Linking Reaction

Five A-B-A′, A-C-A′, B-A-B′, C-A-C′, and C-B-C′ triblock terpolymers with block orders difficult to synthesize by sequential polymerization have been successfully synthesized by a new methodology combining living anionic polymers with a specially designed linking reaction using α-phenylacrylate as the reaction site. Here, A(A′), B(B′), and C(C′) represent groups of polymers (having chain-end anions with different nucleophilicities), which are only polymerizable from A(A′) to B(B′) to C(C′) via sequential polymerization. The corresponding polymers are polystyrene (A) and poly(α-methylstyrene) (A′), poly(2-vinylpyridine) (B) and poly(4-vinylpyridine) (B′) and polymers from methacrylate type monomers like poly(methyl methacrylate) (C), poly(tert-butyl methacrylate) (C′), poly(2-hydroxyethyl methacrylate) (C′), poly(2,3-dihydroxypropyl methacrylate) (C′), and poly(ferrocenylmethyl methacrylate) (C′). Furthermore, three synthetically difficult B-A-B, C-A-C, and C-B-C triblock copolymers with molecular asymmetry in both side blocks have also been synthesized by the developed methodology. All of the polymers thus synthesized are quite new triblock terpolymers and copolymers with well-defined structures, i.e., precisely controlled molecular weights, compositions and narrow molecular weight distributions (M_w/M_n ≤ 1.05).     

Ab initio calculations of isomerization reaction of diphosphene 1-sulfide to thiadiphosphirane

Ab initio Calculations of the isomerization reaction of diphosphene 1-sulfide (2′) to thiadiphosphirane (3′) suggest that the energy barrier of the reaction in the ground state is 25 kcal/mol and that 2′ lies 21 kcal/mol above 3′, while the calculations show that there exists one local minimum on the lowest triplet energy surface.     

Mixed‐Ligand Complexes of Zinc(II) with α‐Hydroxycarboxylates and Aromatic N‐N Donor Ligands: Synthesis,Crystal Structures and Effect of Weak Interactions on their Crystal Packing

Several new two‐ligand complexes of zinc(II) with the aromatic N, N‐donor ligands 2, 2′‐bipyridine or 1, 10‐phenanthroline and one of three different α‐hydroxycarboxylates (HL′) derived of the α‐hydroxycarboxylic acids (H₂L′) (2‐methyllactic, H₂mL; mandelic, H₂M or benzilic, H₂B) were prepared. The compounds of formula [Zn(HL′)₂(NN)]·nH₂O (HL′ = HM, HB) were isolated as white powders and characterized by elemental analysis, IR spectroscopy and thermogravimetric analysis. The complexes of general formula [Zn(HL′)(NN)₂](HL′)·nH₂O (HL′ = HmL, HM) and [Zn(HB)₂(NN)₂], were obtained as single crystals and were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and X‐ray diffractometry. In all cases, the zinc atom is in a distorted octahedral environment. In [Zn(HL′)(NN)₂](HL′)·nH₂O the α‐hydroxycarboxylato ligands behave as bidentate chelating monoanion and an α‐hydroxycarboxylate as counterion is also present. In [Zn(HB)₂(NN)₂], the monoanionic benzilato ligand behaves as monodentate through one oxygen atom of the carboxylate function. The effect of the classical and no‐classical hydrogen bonding and of the π‐π and C‐H…π interactions in the 3D supramolecular arrangement of these molecular complexes is analyzed.