The effects of oligomerization on <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> Mcm4/6/7 function

Background  

Minichromosome maintenance proteins (Mcm) 2, 3, 4, 5, 6 and 7 are related by sequence and form a variety of complexes that unwind DNA, including Mcm4/6/7. A Mcm4/6/7 trimer forms one half of the Mcm2-7 hexameric ring and can be thought of as the catalytic core of Mcm2-7, the replicative helicase in eukaryotic cells. Oligomeric analysis of Mcm4/6/7 suggests that it forms a hexamer containing two Mcm4/6/7 trimers, however, under certain conditions trimeric Mcm4/6/7 has also been observed. The functional significance of the different Mcm4/6/7 oligomeric states has not been assessed. The results of such an assessment would have implications for studies of both Mcm4/6/7 and Mcm2-7.     

Interaction between cucurbit[6]uril and bispyridinecarboxamide

The interaction between cucurbit[6]uril and N,N′-(m-bispyridinecarboxamide)-1,n-alkane (m = 2, 3, 4; n = 4, 6, 8) has been investigated by ¹H-NMR, ESI-MS and single crystal X-ray diffraction method. The results show that cucurbit[6]uril can form pseudorotaxanes with N,N′-(m-bispyridinecarboxamide)-1,6-hexane (m = 2, 3, 4) easily. When the alkyl chain length increases (n = 8), the binding mode is identical, but the binding ability of the host towards guest decreases. In both two cases cucurbit[6]uril shows no selectivity towards positional isomers. However, in the case of n = 4, the binding mode is different, having relations with positional substitution of the guest. Only N,N′-(m-bispyridinecarboxamide)-1,4-butane (m = 2) can form pseudorotaxane with cucurbit[6]uril, while the other two (m = 3, m = 4) form external complex with cucurbit[6]uril. The possible reason for the difference has been discussed.     

芳香叔胺引发丙烯腈光聚合的引发机理

芳香叔胺引发丙烯腈(AN)光聚合是通过形成激基复合物(exciPlex)进行的。紫外光谱和荧光光谱表明,芳香叔胺在基态可以和AN形成电荷转移复合物(CTC),而在激发态可和AN形成exciplc(称定域激发)。CTC经光照亦可激发(称CTC激发)。 定域激发引起光聚合速率为CH_3C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2>HOCH_2·C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2,与芳胺荧光被AN淬灭的Stern-Vo-lmer常数顺序一致。CTC激发引起的光聚合顺序为:CH_3C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2>HOCH_2C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2,与芳胺上取代基推电子能力一致。端基分析表明聚合物有芳胺端基。     

Synthesis and Structure of Bismuth(III)-Containing Noncentrosymmetric Phosphates, Cs(3)KBi(2)M(4)(PO(4))(6)Cl (M = Mn, Fe). Monoclinic (Cc) and Tetragonal (P4(3)) Polymorphs Templated by Chlorine-Centered Cl(Bi(2)Cs) Acentric Units

Single crystals of three new noncentrosymmetric (NCS) phosphates, α (1) and β (2) forms of Cs(3)KBi(2)Mn(4)(PO(4))(6)Cl and α-Cs(3)KBi(2)Fe(4)(PO(4))(6)Cl (3), were grown in a reactive CsCl/KCl molten-salt media. Their structures were determined by single-crystal X-ray diffraction methods showing that the α form crystallizes in the space group Cc (No. 9), which is in one of the 10 NCS polar crystal classes, m (2/m) while the β form crystallizes in P4(3) (No. 78) of another polar class, 4 (4/m). The unit cell parameters of the α form can be approximately correlated with that of the β form via the 3 × 3 orientation matrix [0.5, 0.5, 0; -0.5, 0.5, 0; 0, 0, 2 sin β]. The structures of these otherwise complicated phosphates exhibit two types of channels with circular and elliptical windows where the Cl-centered Cl(Bi(2)Cs) acentric unit is located. The neighboring acentric units are arranged in a parallel fashion in the α form, resulting in the monoclinic (Cc) lattice, but "antiparallel" in the β form, thus giving the tetragonal (P4(3)) unit cell. 1-3 feature the compatible M-O-P unit that contains four crystallographically independent MO(x) (x = 4, 5) polyhedra, which are connected to the Cl(Bi(2)Cs) acentric unit through one short and one long M(II)···Cl bond. The compositions of 1 and 2 consist of three Mn(2+) (d(5)) and one Mn(3+) (d(4)) per formula unit and that of 3 has three Fe(2+) (d(6)) and one Fe(3+) (d(5)). Bond valence sums reveal that, in the α phase, the trivalent site adopts distorted tetrahedral M(1)(3+)O(4) coordination and, in the β phase, distorted trigonal-bipyramidal M(4)(3+)O(5). Thus far, the iron phase has only been isolated in the α form presumably because of little extra stabilization energy gain if the Fe(2+) d(6) ion were to occupy the M(1)O(4) site. The possible origins pertaining to the structural differences in the α and β forms are discussed.     

Facile synthesis of novel 3-quinoxalinyl-1,5-benzodiazepines via ring transformation. Stable tautomers in the 1,5-benzodiazepin-2-one ring system

Novel 3-quinoxalinyl-1,5-benzodiazepines 4, 5, 6, 9, 10 were synthesized via the ring transformation of 3-(N,N-dimethylcarbamoyl)furo[2,3-b]quinoxaline hydrochloride ( 1 ). The 3-quinoxalinyl- 1 ,5-benzodiazepine hydrochlorides 4 and 6 are the tautomers of the N^1′-H (or N⁵-H) form and the C³-H form, respectively, which are stable in solid and solution. However, 4 (NH form) was found to be converted into 6 (C³-H form) by refluxing in acetic acid. The individual spectral evidences and different reactivity of these tautomers are described.     

Synthesis of certain metabolites and analogs of vitamin B6 and their ring-chain tautomerism

Pyridoxol and pyridoxal on benzylation with dimethylphenylbenzylammonium hydroxide (“leucotrope”) gave 3-O-benzylpyridoxol (IV) and 3-O-benzylpyridoxal (V), respectively. As a possible mechanism of this reaction an ion pair intermediate has been postulated. Oxidation of IV and V with chromic oxide-pyridine-acetic acid complex gave 3-O-benzyl-4-pyridoxic acid lactone (VI), which could also be obtained by benzylation of 4-pyridoxic acid. Treatment of VI with dimethylamine gave 2-methyl-3-benzyloxy-5-hydroxymethylpyridine-4-N,N-dimethylcarbox-amide (X) which oxidized to form the 5-formyl derivative (XI). The latter on hydrolysis yielded the metabolite, 2-methyl-3-hydroxy-5-formylpyridine-4-carboxylic acid (I). When reacted with liquid ammonia, VI gave 3-O-benzyl-4-pyridoxamide (VII) which was then oxidized to give 2-methyl-3-benzyloxypyridine-4,5-dicarboxylic acid cyclicimide(IX). Acid hydrolysis of IX gave another metabolite, 2-methyl-3-hydroxypyridine-4,5-dicarboxylic acid (XIII), which could also be obtained by oxidizing XI with potassium permanganate in water to yield 2-methyl-3-benzyloxy-5-carboxypyridine-4-N,N-dimethylcarboxamide (XII) and subsequent hydrolysis with hydrochloric acid. A positional isomer of I, 2-methyl-3-hydroxy-4-formylpyridine-5-carboxylic acid (XVII) was synthesized starting from 3-O-benzyl-5-pyridoxic acid lactone (XIV) following similar reaction sequences used for the preparation of I. Ring-chain tautomerism has been studied in I, XVII, opianic acid (XVIII), phthalaldehydic acid (XIX) and (2-carboxy-4,5-dimethoxy)-phenylacetaldehyde (XX) in different solvents by nmr and in the solid state by ir spectroscopy. A direct and reliable differentiation between the open form (aldehyde proton in low field) and the ring form (lactol proton in the intermediate field) has been obtained by nmr spectroscopy. In sodium deuteroxide and pyridine-d₅ the open chain form existed exclusively (except for homolog (XX) which is in cyclic form in pyridine-d₅), whereas in 18% hydrogen chloride in deuterium oxide all the compounds are completely in the cyclic form. In hexafluoroacetone hydrate-d₂, XVIII, XIX, and XX exist in the cyclic form whereas I is in the open form. In DMS0-d₆ both cyclic and open-chain forms have been observed in XVIII, XIX and XX. Definite peak assignment for the two forms could not be made in I due to broadening or superimposition with C₆-H. The metabolite I, isometabolite (XVII) and opianic acid (XVIII) form cyclic acetyl derivatives which give a sharp lactol peak. In the solid state XVIII, XIX are in the cyclic form and I and XX in the open-chain form as observed by ir spectroscopy.     

Crystal structure and Hirshfeld surface analysis of the anhydrous form of the nucleoside analogue entecavir

The nucleoside analogue entecavir {systematic name: 2‐amino‐9‐[(1S,3R,4S)‐4‐hydroxy‐3‐hydroxymethyl‐2‐methylenecyclopentyl]‐1,9‐dihydro‐6H‐purin‐6‐one}, C₁₂H₁₅N₅O₃, is an antihepatitis B virus drug that has been approved in the US, EU and several countries worldwide. We report here the single‐crystal structure of the anhydrous form and compare it with that of the previously reported monohydrate form [Jiang & Liu (2009). Acta Cryst. E 65 , o2232]. Hirshfeld surface analysis has been employed to understand and visualize the subtle packing differences between the two crystalline forms. The results show that, compared to the previously reported hydrated form, the anhydrous crystal has significantly different intermolecular interactions and packing patterns.     

[C6N2H18]2[Mo5O15(HPO4)2]·H2O的水热合成与结构表征

通过水热法合成了一个新化合物[C6N2H18]2[Mo5O15(HPO4)2]·H2O,并通过IR光谱、ICP、元素分析、差热与热重分析和X射线单晶衍射分析等手段进行了表征.结果表明,晶体属三方晶系,P3(2)21空间群,a=1.1231(1)nm,c=2.2802(5)nm,V=2.4911(7)nm3,Dx=2.835Mg/m3,Z=6,最后的一致性因子R=0.0227,wR=0.0675.阴离子中Mo5O15构成一环状结构,2个HPO4一个连在环的下方,一个连在环的上方,形成类似于“飞碟”状的结构,阳离子为2个质子化的四甲基乙二胺.     

Versatility of heterocyclic thioamides in the construction of a trinuclear cluster [Cu3I3(dppe)3 (SC5H4NH)] and Cu(I) linear polymers {Cu6(SC5H4NH)6I6}n x 2nCH3CN and {Cu(I)6 (SC3H6N2)6X6}n (X = Br, I)

Reaction of copper(I) iodide with pyridine-2-thione (2-SC5H4NH) and 1,2-bis(diphenylphosphino)ethane (dppe) in a CH3CN-CHCl3 mixture yielded a triangular cluster, [Cu3I3(mu2-P,P-dppe)3 (eta1-SC5H4NH)], 1. Similar reaction with 2-SC5H4NH and a series of diphosphanes, Ph2P-X-Ph2P {X = -CH2- (dppm), -(CH2)3- (dppp), -(CH2)4- (dppb), -CH=CH- (dppen)}, gave a novel iodo-bridged hexanuclear Cu(I) linear polymer,{Cu6(mu3-SC5H4NH)4 (mu2-SC5H4NH)2 (I4)(mu-I)2-}n x 2nCH3CN, 2. Reactions of copper(I) iodide/copper(I) bromide with 1,3-imidazolidine-2-thione (SC3H6N2) in a CH3CN-CHCl3 mixture yielded hexanuclear Cu(I) linear chain polymers, [{Cu6(mu3-SC3H6N2)2 (mu2-SC3H6N2)4X2 (mu-X)4}n] (X = Br, 4; I, 5). In compound 1, two iodide atoms and one dppe form the dinuclear Cu(mu2-I)2 (mu2-dppe)Cu core, and two dppe ligands bridge this core with the third Cu(I) center coordinated to 2-SC5H4NH via the S atom. The chain polymer 2 has a centrosymmetric hexanuclear central core, Cu6S6I4 (mu-I)2--, formed by dimerization of six-membered trinuclear motifs, Cu3(mu2-SC3H6N2)3I3 via (mu3-S) bonding modes of the thione ligand, and has four terminal and two bridging iodine atoms in trans-orientations. Linear chains are separated by the nonbonded acetonitrile molecules. In 4 and 5, three copper(I) bromide or copper(I) iodide moieties and three SC3H6N2 ligands combined via bridging S donor atoms to form the six-membered trinuclear Cu3(mu2-SC3H6N2)3I3 cores which polymerized via S and X atoms in a side-on fashion to form linear chain polymers, [{Cu6(mu3-SC3H6N2)2 (mu2-SC3H6N2)4X2(mu-X)4}n]. The (mu3-S) modes of bonding of neutral heterocyclic thioamides are first examples, as are trinuclear cluster and linear polymers rare examples in copper chemistry.     

膦手性丙炔胺脯氨酸磷酸酯螺旋聚合物的合成与表征

通过添加对映体拆分剂,合成了4种含膦手性的丙炔胺磷酸酯单体[HC帒CC H2NH(PO)R1R2].单体1,R1=OPh,R2=NC4H7COOCH3;单体2,R1=OPh,R2=NC4H7COOCH2CH3;单体3,R1=OPh,R2=NC4H7-COOC(CH3)3;单体4,R1=Ph,R2=NC4H7COOC(CH3)3].1H-NMR和31P-NMR表征可知对映体(单体1)不能被拆分剂拆分,而单体2、单体3、单体4通过拆分剂可以制得单一手性的磷化合物.以(nbd)Rh+[η6-C6H5B--(C6H5)3]为催化剂,以三氯甲烷为溶剂成功得到聚合物分子量范围在0.4×10-4～0.7×10-4,分子量分布在1.26～1.98范围的3种含手性膦侧基的丙炔胺类聚合物.比旋光度([α]D)、圆二色谱(CD)对聚合物的不同侧基及温度对光学活性的影响表明,聚合物具有良好的光学活性且能够形成单一方向的螺旋构象,说明膦手性在构建螺旋聚合物具有重要作用.     

Enantioselective total synthesis of isoedunol and beta-araneosene featuring unconventional strategy and methodology

A new synthetic strategy for the enantioselective synthesis of members of the dolabellane family of marine natural products has been demonstrated for the specific examples beta-araneosene and isoedunol (1 and 2, respectively) by the pathway outlined in Scheme 1. Key steps include (1) diastereoselective alkylation of Seebach's chiral lactate acetal (6) by the iodide derived from 5; (2) Kulinkovich ethylenation of ester 9 to form the cyclopropanol 10; (3) ring expansion of 10 to form 11; (4) pinacol cyclization of keto aldehyde 12 to form 13a; (5) rearrangement of 13b to 14; (6) propenylation of 14 to 2; and (7) reductive pi-transposition to form 1.     

α'-(BEDT-TTF)_2C_6H_4(SO_3)_2的合成、结构与导电性

用恒电流电化学结晶法合成了一种新的基于BEDT-TIF的电荷转移盐α'-(BEDT- TIF)_2C_6H_4(SO_3)_2 [BEDT-TIF = 双亚乙基二硫四硫富瓦烯,C_6H_4(SO_3) _2~(2-) = 对苯二磺酸根]。通过四圆X射线衍射方法测定了α'-(BEDT-TTF) _2C_6H_4-(SO_3)_2的结构。晶体属于单斜晶系,P2/n空间群;晶胞参数：a = 0. 77937(17)nm, b = 0.66989(11) nm, c = 3.4422 (7) nm, β = 91.135(12) °, V = 1.7968(6) nm~3。该晶体中BEDT-TTF~+自由基沿a轴方向形成具有二聚体结构 的交错排列型柱状堆积,沿b轴方向由户并户强分子间相互作用形成一维分子链。 电荷补偿阴离子C_6H_4(SO_3)_2~(2-)则在a方向存在较强的作用。沿c轴方向, BEDT-TTF~+自由基层和阴离子层交替排列形成夹心式结构。α'-(BEDT-TTF) _2C_6H_4-(SO_3)_2在ab面的某方向的室温电导率为0.5913 Ω~(-1)·m~(-1),电 阻率-温度测定曲线表明它具有半导体导电行为。在150K附近,晶体发生了某种相 变。     

Complex Salts Derived from the Reactions of Organotin(IV) with 6-Methylpyridine-2-Carboxaldehyde Phenylhydrazone: X-Ray Crystal Structure of BIS[6-Methylpyridine- 2-Carboxaldehydehydrazodium]- Tetrachlorodimethylstannate(IV)

Reactions of organotin(IV) chloride (Me 2 SnCl 2 , PhSnCl 3 and n -BuSnCl 3 ) with the Schiff base 6-methylpyridine-2-carboxaldehyde phenylhydrazone ( L ) result in the formation of organotin(IV) anionic complexes. Me 2 SnCl 2 reacts with L in dichloromethane to form [ L H + ] 2 [Me 2 SnCl 4 ] 2 m . X-ray structural analysis has been carried out on the complex salt bis[6-methylpyridine-2-carboxaldehydehydrazodium]tetra-chlorodimethylstannate(IV), [ L H + ] 2 [Me 2 SnCl 4 ] 2 m wherein the tin moieties exist as monomers. Reactions of PhSnC1 3 and n -BuSnCl 3 with L form the complexes [ L H + ] 2 [PhSnCl 5 ] 2 m and [ L H + ] 2 [ n- BuSnCl 5 ] 2 m . Compounds were also characterized by FTIR, 1 H and 13 C NMR spectroscopy.     

Biosynthesis of 1-deoxy-1-imino-D-erythrose 4-phosphate: a defining metabolite in the aminoshikimate pathway.

With respect to the source of the nitrogen atom incorporated into the aminoshikimate pathway, d-erythrose 4-phosphate has been proposed to undergo a transamination reaction resulting in formation of 1-deoxy-1-imino-d-erythrose 4-phosphate. Condensation of this metabolite with phosphoenolpyruvate catalyzed by aminoDAHP synthase would then hypothetically form the 4-amino-3,4-dideoxy-d-arabino-heptulosonic acid 7-phosphate (aminoDAHP), which is the first committed intermediate of the aminoshikimate pathway. However, in vitro formation of aminoDAHP has not been observed. In this account, the possibility is examined that 3-amino-3-deoxy-d-fructose 6-phosphate is the source of the nitrogen atom of the aminoshikimate pathway. Transketolase-catalyzed ketol transfer from 3-amino-3-deoxy-d-fructose 6-phosphate to d-ribose 5-phosphate would hypothetically release 1-deoxy-1-imino-d-erythrose 4-phosphate. Along these lines, a chemoenzymatic synthesis of 3-amino-3-deoxy-d-fructose 6-phosphate was elaborated. Incubation of 3-amino-3-deoxy-d-fructose 6-phosphate in Amycolatopsis mediterranei crude cell lysate with d-ribose 5-phosphate and phosphoenolpyruvate resulted in the formation of aminoDAHP and 3-amino-5-hydroxybenzoic acid. 3-[15N]-Amino-3-deoxy-d-6,6-[2H2]-fructose 6-phosphate was also synthesized and similarly incubated in A. mediterranei crude cell lysate. Retention of both 15N and 2H2 labeling in product aminoDAHP indicates that 3-amino-3-deoxy-d-fructose 6-phosphate is serving as a sequestered form of 1-deoxy-1-imino-d-erythrose 4-phosphate.     

A General Diversified Synthesis of Carbazoles and the First Synthesis of Karapinchamine A

[IPrAuCl]/AgSbF₆‐catalyzed cyclization of the readily available 4‐benzoxyl‐1‐(indol‐2‐yl)‐2‐alkynols occurred smoothly in 1,2‐dichloroethane (DCE) in the presence of 4 Å MS to form a series of differently polysubstituted 2‐oxygenated carbazole derivatives efficiently. Based on mechanistic study, a possible mechanism involving 1,3‐migration of a benzoate group to form the allene, Au⁺‐mediated cyclization–elimination to form a gold–carbene intermediate, and subsequent highly selective 1,2‐migration has been proposed for the formation of carbazoles. Highly selective 1,2‐migration referring to the two substituents R³ and R⁴ (R⁴=H, alkyl, and aryl group) was observed: (1) In the presence of both H and alkyl groups, 1,2‐hydrogen migration is exclusive; (2) in the presence of a methyl group (R³), propyl, isopropyl, 4‐methylphenyl, and 4‐chlorophenyl groups (R⁴) migrate exclusively. Finally, the first total synthesis of the recently isolated naturally occurring carbazole alkaloid karapinchamine A in 5.2 g scale has been realized in 6 steps from commercially available chemicals without need for any protection–deprotection.     

π -Type and σ -type cation- π complexes of atomic cations

MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B⁺ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li⁺, N⁺, Na⁺, P⁺ and K⁺ form -type complexes, whereas H⁺, F⁺, and Cl⁺ form covalent -type complexes. With benzene Li⁺, B⁺, Na⁺, Al⁺, and K⁺ form -type complexes whereas H⁺, F⁺, and Cl⁺ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction.     

Unraveling the photochemistry of Fe(CO)5 in solution: observation of Fe(CO)3 and the conversion between 3Fe(CO)4 and 1Fe(CO)4(Solvent)

The photochemistry of Fe(CO)5 (5) has been studied in heptane, supercritical (sc) Ar, scXe, and scCH4 using time-resolved infrared spectroscopy (TRIR). 3Fe(CO)4 ((3)4) and Fe(CO)3(solvent) (3) are formed as primary photoproducts within the first few picoseconds. Complex 3 is formed via a single-photon process. In heptane, scCH4, and scXe, (3)4 decays to form (1)4 x L (L = heptane, CH4, or Xe) as well as reacting with 5 to form Fe2(CO)9. In heptane, 3 reacts with CO to form (1)4 x L. The conversion of (3)4 to (1)4 x L has been monitored directly for the first time (L = heptane, kobs = 7.8(+/- 0.3) x 10(7) s(-1); scCH4, 5(+/- 1) x 10(6) s(-1); scXe, 2.1(+/- 0.1) x 10(7) s(-1)). In scAr, (3)4 and 3 react with CO to form 5 and (3)4, respectively. We have determined the rate constant (kCO = 1.2 x 10(7) dm3 mol(-1) s(-1)) for the reaction of (3)4 with CO in scAr, and this is very similar to the value obtained previously in the gas phase. Doping the scAr with either Xe or CH4 resulted in (3)4 reacting with Xe or CH4 to form (1)4 x Xe or (1)4 x CH4. The relative yield, [(3)4]:[3] decreases in the order heptane > scXe > scCH4 > scAr, and pressure-dependent measurements in scAr and scCH4 indicate an influence of the solvent density on this ratio.     

A cyclic hexamer of silver trifluoroacetate supported by four triphenylphosphine sulfide template molecules

Crystallization of silver trifluoroacetate from chloroform solutions containing triphenylphosphine sulfide affords a trigonal and a monoclinic form of a 6:4 complex {[CF3C(O)OAg]6(Ph3PS)4} of C2 symmetry with different amounts of chloroform in the crystals. With the Ph3PS components as template molecules, the CF3C(O)OAg units are assembled to form a 6-membered metallacycle codetermined by metallophilic bonding and enclosed by a 24-membered ring [AgOCO]6. A complex of the type [LAgOC(O)CF3]2, with L representing the isocyanide ligand pTolSO2CH2NC, has been shown to have a conventional bicyclic structure with three-coordinate silver atoms engaged in transannular metallophilic interactions.     

Synthesis of benzo[g]quinoline derivatives

A method for the synthesis of 3-substituted benzo[g]quinolin-4-ones by the condensation of 1,2,3,4-tetrahydrobenzo[g]quinolin-4-one with aromatic aldehydes in an alkaline medium has been developed. It has been found that the first stage of the reaction is the formation of the corresponding benzylidene derivative, which then isomerizes into the more stable benzyl derivative. The structure of the 3-substituted benzo[g]quinolin-4-ones obtained, as existing in the tautomeric oxo form, is confirmed by their IR and UV spectra.For Communication VI, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinii, Vol. 6, No. 6, pp. 798–801, June, 1970.     

Synthesis,structures, and conformational characteristics of calixarene monoanions and dianions

The synthesis, complete characterization, and solid state structural and solution conformation determination of calix[n]arenes (n = 4, 6, 8) is reported. A complete series of X-ray structures of the alkali metal salts of calix[4]arene (HC4) illustrate the great influence of the alkali metal ion on the solid state structure of calixanions (e.g., the Li salt of monoanionic HC4 is a monomer; the Na salt of monoanionic HC4 forms a dimer; and the K, Rb, and Cs salts exist in polymeric forms). Solution NMR spectra of alkali metal salts of monoanionic calix[4]arenes indicate that they have the cone conformation in solution. Variable-temperature NMR spectra of salts HC4.M (M = Li, Na, K, Rb, Cs) show that they possess similar coalescence temperatures, all higher than that of HC4. Due to steric hindrance from tert-butyl groups in the para position of p-tert-butylcalix[4]arene (Bu(t)C4), the alkali metal salts of monoanionic Bu(t)C4 exist in monomeric or dimeric form in the solid state. Calix[6]arene (HC6) and p-tert-butylcalix[6]arene (Bu(t)C6) were treated with a 2:1 molar ratio of M(2)CO(3) (M = K, Rb, Cs) or a 1:1 molar ratio of MOC(CH(3))(3) (M = Li, Na) to give calix[6]arene monoanions, but calix[6]arenes react in a 1:1 molar ratio with M(2)CO(3) (M = K, Rb, Cs) to afford calix[6]arene dianions. Calix[8]arene (HC8) and p-tert-butylcalix[8]arene (Bu(t)()C8) have similar reactivity. The alkali metal salts of monoanionic calix[6]arenes are more conformationally flexible than the alkali metal salts of dianionic calix[6]arenes, which has been shown by their solution NMR spectra. X-ray crystal structures of HC6.Li and HC6.Cs indicate that the size of the alkali metal has some influence on the conformation of calixanions; for example, HC6.Li has a cone-like conformation, and HC6.Cs has a 1,2,3-alternate conformation. The calix[6]arene dianions show roughly the same structural architecture, and the salts tend to form polymeric chains. For most calixarene salts cation-pi arene interactions were observed.