Nanomolar binding of peptides containing noncanonical amino acids by a synthetic receptor

This paper describes the molecular recognition of phenylalanine derivatives and their peptides by the synthetic receptor cucurbit[7]uril (Q7). The 4-tert-butyl and 4-aminomethyl derivatives of phenylalanine (tBuPhe and AMPhe) were identified from a screen to have 20-30-fold higher affinity than phenylalanine for Q7. Placement of these residues at the N-terminus of model tripeptides (X-Gly-Gly), resulted in no change in affinity for tBuPhe-Gly-Gly, but a remarkable 500-fold increase in affinity for AMPhe-Gly-Gly, which bound to Q7 with an equilibrium dissociation constant (K(d)) value of 0.95 nM in neutral phosphate buffer. Structure-activity studies revealed that three functional groups work in a positively cooperative manner to achieve this extraordinary stability (1) the N-terminal ammonium group, (2) the side chain ammonium group, and (3) the peptide backbone. Addition of the aminomethyl group to Phe substantially improved the selectivity for peptide versus amino acid and for an N-terminal vs nonterminal position. Importantly, Q7 binds to N-terminal AMPhe several orders of magnitude more tightly than any of the canonical amino acid residues. The high affinity, single-site selectivity, and small modification in this system make it attractive for the development of minimal affinity tags.     

Polyetherimides. I. Preparation of dianhydrides containing aromatic ether groups

A general synthetic method and characterization of bis(ether anhydride)s, the ether containing aromatic dianhydrides of the following structure, are presented. The method involves aromatic nitro-displacement of N-substituted 3- or 4-nitrophthalimide with bisphenoxides to form N-substituted arylene-bis(phthalimido)ethers or bis(ether imide)s. Sixteen structurally different bis(ether imide)s have been prepared and subsequently converted to the corresponding bis(ether anhydride)s. Bis(ether anhydride)s are stable crystalline compounds of a moderate reactivity. Unlike highly reactive dianydrides such as pyromellitic and benzophenonetetracarboxylic dianhydrides bis(ether anhydride)s are semipermanently stable against hydrolysis in the presence of atmospheric moisture.     

Solid phase synthesis and opioid receptor binding activities of [D-Ala2, D-Leu5]enkephalin analogs containing a fluorinated aromatic amino acid

Five [D-Ala2, D-Leu55]enkephalin (DADLE) analogs containing fluorinated Tyr1 or Phe4 residue, that is, [Phe(2F)4] (I), [Phe(3F)4] (II), [Phe(4F)4] (III), [Tyr(3F)1] (IV) and [Tyr(2F)1] (V), were synthesized by the solid phase method and their opioid receptor affinities were examined. Affinity profiles of five derivatives for the mu- and delta-receptor were similar to those of DADLE, and the affinity for kappa-receptor was zero or negligible.     

The structure of a carbon monoxide adduct of zeolite 5A

The structure of Ca₅Na₂-A:5CO has been determined at room temperature using Rietveld profile refinement in space groupFm3c witha refined to 24.6558(2)A˚. The finalR_pw was 3.5%. As in the case of dehydrated zeolite 5A, the exchangeable cations are located in S1 (6-ring) sites, with Ca-O and Na-O distances of 2.32 and 2.37A˚. The carbon atoms of the carbon monoxide molecules have been located on the three-fold axis in the α-cage in a position analogous to that found in the CO complex of cobalt-exchanged zeolite A. However, the oxygen atoms are either undergoing considerable thermal motion or are disordered over several off-axis locations. The Ca-C distance is 2.83A˚. Inside the β-cage, with site occupancy approximately three-fourths, there are AlO₄H₃ tetrahedral species evenly distributed between two orientations, as has been found previously in studies of divalent exchanged samples of zeolite A. This aluminum complex bonds to the framework via Al-O-H … O(3) hydrogen bonds and there is coordination of the non-hydrogen-bearing oxygen atom to exchangeable calcium ions (Al-O … Ca).     

Synthesis and characterization of aromatic polymers containing pendant silyl groups. I. Polyarylates

Polyarylates containing pendant silyl group were prepared by the phase-transfer catalyzed, two-phase polycondensations of 2,2-bis (4-hydroxyphenyl) propane with corresponding dicarbonyl chlorides such as 2-trimethylsilylterephthaloyl chloride, 5-trimethylsilylisophthaloyl chloride, 5-dimethylphenylsilylisophthaloyl chloride, and 5-triphenylsilylisophthaloyl chloride. The resulting amorphous polyarylates with glass transition temperatures of 163–214°C had inherent viscosities in the range of 0.41–0.95 dL/g. These polyarylates were readily soluble in common chlorinated hydrocarbons and it was possible to obtain transparent, flexible, and tough films from the polymer solutions. The prepared polyarylates showed fairly good thermal stabilities as well as tensile strengths, i.e., the tensile strengths of the cast films from chloroform solution were 6.0–6.7 kg/mm². And TGA data revealed 10% weight losses and residual weights at 800°C were 437–495°C and 27–40% under nitrogen atmosphere, respectively. © 1992 John Wiley & Sons, Inc.     

Polyfunctional macroheterocycles. 1. Synthesis of sulfur-containing macroheterocycles with endocyclic amido or sulfonamido groups

The reaction of 1,8-diamino-, 1,8-bis(2-carbomethoxyethylamino)-, and 1,8-bis(2-phenylethylamino)-3,6-dithiaoctanes and 1,2-bis(2-aminoethylthiomethyl)-4,5-dimethylbenzene with adipic, phthalic, and terephthalic acid dichlorides leads to the corresponding sulfur-containing macrocyclic diamines. Macrocycles that contain endocyclic sulfonamido groups are formed in the reaction of benzene-1,3-disulfonic acid dichloride with hexamethylenediamine and 1,8-bis(2-carbomethoxyethylamino)-3,6-dithiaoctane. The oxidation of 9,10-benzo-8,11-dioxo-7,12-bis-(2-carbomethoxyethyl)-1,4-dithia-7,12-diazacyclotetradec-9-ene with 30% hydrogen peroxide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 995–998, July, 1988.     

Crystal structure of the molecular adduct of antimony(III) fluoride with L-phenylalanine

The crystal structure of a newly synthesized molecular adduct of antimony(III) fluoride with L-phenylalanine of the composition SbF₃(C₉H₁₁NO₂) is determined for the first time (monoclinic crystal system: a = 5.8742(1) ?, b = 6.2079(1) ?, c = 15.5401(3) ?, β = 90.741(1)°, Z = 2, P2₁ space group). The structure consists of SbF₃ molecules and L-phenylalanine bound into polymer chains by bidentate bridging carboxyl groups of amino acid molecules. Weak Sb⋯F(3)^b bonds organize the adjacent chains into polymer ribbons that are bound into layers by N-H⋯F and N-H⋯O hydrogen bonds.     

Synthesis and characterization of aromatic polymers containing pendant silyl groups. II. Aromatic polyamides

In order to improve the solubility of aromatic polyamides without significant loss of thermal stability, synthesis of aromatic polyamides containing pendant silyl groups was carried out by direct polycondensation of silylated aromatic diacids such as 2-trimethylsilylterephthalic acid (TSTA), 2,5-bis (trimethylsilyl) terephthalic acid (BTSTA), 5-trimethylsilylisophthalic acid (TSIA), 5-dimethylphenylsilylisophthalic acid (DMSIA), and 5-triphenylsilylisophthalic acid (TPSIA) with various aromatic diamines. The resulting polyamides had inherent viscosities in the range of 0.18–1.10 dL/g and showed improved solubilities toward aprotic polar solvents such as NMP, DMF, DMSO, etc. The prepared aromatic polyamides exhibited fairly good thermal stabilities, which were almost comparable to those of corresponding nonsubstituted aromatic polyamides. That is, thermogravimetric analysis (TGA) data revealed 10% weight losses at 358–500°C and residual weights at 700°C were 46–67% under nitrogen atmosphere. © 1992 John Wiley & Sons, Inc.     

Synthesis and properties of aromatic polyamides containing the cyclohexane structure

1,1-Bis[4-(4-carboxyphenoxy)phenyl]cyclohexane (III) and 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (V) were prepared in two main steps starting from the aromatic nucleophilic substitution of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with 1,1-bis(4-hydroxyphenyl)cyclohexane in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Using triphenyl phosphite and pyridine as condensing agents, two series of polyamides with cyclohexylidene cardo groups were directly polycondensated from dicarboxylic acid III with various aromatic diamines or from diamine V with various aromatic dicarboxylic acids in an N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The polyamides exhibited inherent viscosities in the range of 0.45 to 1.78 dL/g. Almost all of the polymers were readily soluble in polar aprotic solvents such as NMP and N,N-dimethylacetamide (DMAc) and could afford transparent, flexible, and tough films by solution casting. The glass transition temperatures (T_g) of these aromatic polyamides were in the range of 180–243°C by DSC, and the 10% weight loss temperatures in nitrogen and air were all above 450°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3575–3583, 1999     

Anion conductive aromatic polymers containing fluorenyl groups: Effect of the position and number of ammonium groups

Synthesis and properties of anion conductive aromatic block copolymers, QPE‐bl‐3, QPE‐bl‐3 M2, and M4, containing fluorenylidene biphenylene groups as scaffold for ammonium groups are described. These copolymers share the same main chain structure, but the position and the number of ammonium groups on a fluorenyl group differ. High molecular weight quaternized block copolymers were obtained via typical chloromethylation reaction or using preaminated monomers, and were well‐characterized by ¹H NMR spectra. Self‐standing bendable membranes were obtained by solution casting. QPE‐bl‐3 M4 membranes containing four ammonium groups per hydrophilic repeat unit (highest ammonium density) in the hydrophilic block exhibited well developed phase‐separated morphology, while QPE‐bl‐3 membranes containing two ammonium groups per hydrophilic repeat unit exhibited high anion conductivity. The highest anion conductivity (104 mS/cm) was obtained with QPE‐bl‐3 membrane (IEC = 2.1 meq/g) at 80 °C in water. An H₂/O₂ alkaline fuel cell was operable with the membrane to achieve 62 mW/cm² of the maximum power density at 161 mA/cm² of the current density. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 935–944     

Crystal structure of the 1:2:2 adduct of piperazine, o-phthalic acid and water.

The adduct of piperazine, o-phthalic acid and water (1:2:2), C20H26N2O10, crystallizes in the monoclinic space group P21/c with a = 6.129(1), b = 12.810(2), c = 13.137(2)A, beta = 95.87(1) degrees, V = 1026.0(3)A3, Z = 2. The piperazinium adopts a chair comformer, and is tied with the hydrogen orthophthalate via a hydrogen bond of the N-H...O type. Because of bifurcated hydrogen bonding of C(sp3)H-O [3.0801(17) and 3.1408(18)A] and the shortest hydrogen bond of C(sp3)H-O [2.9758(17)A], C(sp3)H-O hydrogen bonds play important roles in stablizing the title adduct.