A novel route to synthesize Freidinger lactams by micowave irradiation.

The incorporation of a Freidinger-like lactam structure into the backbone of peptides has been proven to be an useful strategy in the design of a variety of conformationally restricted targets. Several different strategies have been developed toward Freidinger lactams but no one resulted to be completely facile. Here, we report an efficient strategy that involves the iodo-derivatives in side chain of an appropriate amino acid used as electrophilic agent, and the standard solid phase peptide synthesis assisted by microwave irradiation. The methodology developed could be useful to perform Freidinger-like lactams with defined stereochemistry for routine use in solid phase peptide chemistry.     

9-Fluorenylmethyloxycarbonyl/ tbutyl-based convergent protein synthesis

Besides linear solid phase peptide synthesis, segment condensation in solution and chemical ligation, convergent peptide synthesis (CPS) was developed in order to enable the efficient preparation of complex peptides and small proteins. According to this synthetic strategy, solid phase synthesized and suitably protected peptide fragments corresponding to the entire peptide/protein-sequence are condensed on a solid support or in solution, to the target protein. This review summarizes CPS performed utilizing the mild 9-fluorenylmethyloxycarbonyl/tbutyloxycarbonyl-based protecting scheme for the amino acids.     

Solid phase synthesis of [18F]labelled peptides for positron emission tomography

A strategy for the solid phase synthesis of [18F]labelled peptides has been developed. The peptides were prepared on solid support and acylated with 4-[18F]fluorobenzoic acid using HATU within 3 min and the labelled peptide was released from the solid support within 7 min. The [18F]labelled peptides were produced in good purity with a specific activity of 20-25 GBq/micromol.     

Solution versus solid-phase cyclization strategies for large sidechain lactam-bridged peptides: A comparative study

A 22-residue peptide with a sidechain lactam bridge involving 18 residues (60-atom cycle) has been synthesized. Three different protection schemes using Fmoc/^tBu/cyclohexyl, Fmoc/^tBu/allyl or Boc/Bzl/ fluorenylmethyl protecting group combinations have been explored for the solid phase of the linear precursors, which have been subsequently cyclized in solution or in the solid phase. Cyclization yields in solution have been consistently better than on solid phase; however, the solid-phase strategy requires fewer purification steps and therefore global yields are comparable.     

Solid support post-conjugation of amino acids and a phenanthroline derivative to a central position in peptide nucleic acids

A solid phase synthesis strategy for post-conjugation of amino acids and a phenanthroline derivative to peptide nucleic acids is described. The peptide nucleic acids, synthesized by 9-fluorenylmethyloxycarbonyl chemistry on TentaGel S Rink Amide resin, have an internally placed unit carrying an amino linker with 4-methyltrityl protection. Methyltrityl removal by mild acidic conditions and conjugation of amino acids or a phenanthroline derivative, via an amide or urea linker, was performed on-resin after completion of the chain assembly. This solid phase methodology resulted in excellent purities of the crude conjugates.     

Solid (gel) phase synthesis of fully-protected acylpeptide hydrazides with hydrazine-labile sidechains

A simple, efficient strategy for the preparation of fully-protected acylpeptide hydrazides with hydrazine-labile sidechains is described. The method involves controlled hydrazinolytic cleavage of target peptides from assemblies elaborated by solid (gel) phase synthesis on phenolic peptide resins.     

Solid-phase synthesis of second-generation polyproline dendrimers

Second-generation dendrimers have been prepared on solid phase by successive additions of branched polyproline building blocks starting from two different branching units anchored to the solid support. The preparation of Pro-rich building blocks was carried out by stepwise solid-phase synthesis and their iterative addition was performed by a convergent approach, also using solid-phase synthesis. cis-4-Amino-L-proline and imidazolidine-2-carboxylic acid were used as branching units due to their structural resemblance to proline. The optimized strategy allowed the target compounds to be obtained with high purities without the need for purification steps.     

Importance of surface properties of affinity resin for capturing a target protein,Cyclooxygenase-1

We have prepared affinity resins based on two kinds of solid phases, including a commercially available solid phase, to re-realize the importance of surface properties of affinity resins such as controlled ligand density as well as existential surroundings of the ligand. Affinity resins were prepared using non-steroidal anti-inflammatory drugs, such as Ketoprofen, Ibuprofen, and Aspirin, having different activities as ligands. The ligand density was controlled through two different strategies: one strategy was that the solid phases having different amino group densities (20, 60, 100, 125 μmol/ml) were utilized then, Ketoprofen was fully immobilized through condensation reaction to amino groups; another strategy was that a solid phase having amino group density (125 μmol/ml) was utilized then, each ligand was immobilized with controlled immobilization rate. In addition, a typical hydrophobic group, stearoyl group (C₁₈ group), was immobilized on the affinity resin with controlled ligand immobilization rate to change the existential surroundings of the ligand. Affinity tests were performed for Cyclooxgenase-1 (COX-1) as it was the target protein in this work. The amount of captured COX-1 was evaluated utilizing each affinity resin. It was suggested that the density of surface ligand tends to relate to the amount of captured COX-1 on our solid phase-based affinity resins; however, several exceptions occurred according to the surface properties of affinity resins in the case of commercial one.     

Semi‐automated high throughput combinatorial solid‐phase organic synthesis

A semi‐automated technique for massive parallel solid‐phase organic synthesis based on a “split only” strategy is described. Two different types of purpose‐oriented reaction vessels are used. The initial steps are performed in domino blocks, and the resin‐bound intermediates then split into wells of a micro plate for the last combinatorial step. The domino block is a reaction block for manual and semi‐automatic parallel solid‐phase organic synthesis that simplifies liquid exchange and integrates common synthetic steps. The synthesis in micro plates does not use any filter for separation of resin beads from the supernatant liquid, and allows high throughput parallel synthesis on solid phase to be performed. This technique, documented on examples of diverse disubstituted benzenes, includes the use of gaseous cleavage in the last synthetic step and allows the synthesis of thousands of compounds per day in mg quantities. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng (Comb Chem) 61:135–141, 1998/1999.     

Insertion of an internal dipeptide into PNA oligomers: thermal melting studies and further functionalization

The solid phase synthesis of PNA oligomers with the internal dipeptide Gly-Phe is presented and the interaction with complementary DNA investigated. UV absorbance melting experiments with different but complementary DNA sequences show that stable PNA x DNA duplexes are only obtained when there is no DNA base opposite the dipeptide unit. Instead, the dipeptide spacer forms a loop-like structure within the duplex. Further functionalization with N-heterocyclic ligands is described. p-Nitro-phenylalanine is introduced in place of Phe during solid phase synthesis and subsequently reduced to p-amino-phenylalanine. Reaction with activated acids provides the ligand conjugates in high yield and purity. This strategy opens a universal route to a large number of internal substitutions in PNA chemistry.     

Polymer-supported biopolymer synthesis: 1. High load solid (gel) phase strategy for peptide synthesis with a phenolic poly(acryloylmorpholine)-based support

An efficient, low-cost, reaction strategy for the solid (gel) phase synthesis of peptides and protected peptide segments has been developed. The strategy involves the use of a new poly(acryloylmorpholine)-based phenolic support matrix, Koch-Light Peptide Resin A. Illustrative syntheses of N-terminal Boc- and Z-protected[Leu]- enkephalin derivatives, including C-terminal acid hydrazides and esters, are described. The strategy, which is effective for the synthesis of peptides at high matrix loadings, is adopted readily for large-scale application.     

Enzymatic purification of chemically synthesized oligodeoxyribonucleotides prior to removal from a solid-support

A novel combined solid-phase DNA synthesis and solid-phase DNA purification strategy is described. Removal of all N-, cap-, and phosphate protecting groups while maintaining a 5'-blocking group on the final product followed by a 5'- specific exonuclease digestion of failure sequences with the synthetic DNA still attached to the solid phase yields an essentially pure oligomer.     

Brown tree snakes effectively removed from a large plot of land on Guam by perimeter trapping

The brown tree snake introduction to Guam has had serious environmental, economic and social consequences. Trapping brown tree snakes in the vicinities of ports and other cargo staging facilities is central to a program implemented to deter its dispersal from Guam. Trapping forested plots on their perimeters has been an efficient and effective trap placement strategy for removing brown tree snakes from plots up to 8.4 ha. Here we examined whether this trap placement strategy was effective on a 17.8 ha plot, over twice the size of plot for which there was solid evidence of perimeter trapping’s efficacy. We found that brown tree snakes were removed according to an exponential decay function. From 7 weeks on of trapping, snake captures had declined to low steady state levels that may best reflect population recruitment in the plot. After 22 weeks of trapping, both the plot interior and perimeter were trapped in a second phase designed to determine if the central portion of the plot contained reservoirs of brown tree snake populations. The second trapping phase lasted for 8 weeks and produced the same low, steady state capture rates as the final 16 weeks of the first phase that used only perimeter trapping. Only five snakes were captured in the plot interior in the second phase. We concluded that perimeter trapping removed brown tree snakes throughout the plot and the strategy could be applied to larger plots than demonstrated previously.     

Solid-phase library synthesis of reversed-statine type inhibitors of the malarial aspartyl proteases plasmepsin I and II

With the aim to develop inhibitors of the plasmepsin I and II aspartic proteases of the malaria parasite Plasmodium falciparum, we have synthesized sets of libraries from novel reversed-statine isosteres, using a combination of solution phase and solid phase chemistry. The synthetic strategy furnishes the library compounds in good to high overall yields and with excellent stereochemical control throughout the developed route. The products were evaluated for their plasmepsin I and II inhibiting properties and were found to exhibit modest but promising activity. The best inhibitor exhibits an in vitro activity of 28% inhibition of plasmepsin II at an inhibitor concentration of 0.5 microM (K(i) for Plm II=5.4 microM).     

Synthesis and biological evaluation of enantiopure thionitrites: the solid-phase synthesis and nitrosation of D-glutathione as a molecular probe

The D-isomer of the naturally-occurring tripeptide glutathione (gamma-L-Glu-L-Cys-Gly, L-GSH) has been synthesised using the Fmoc solid phase peptide synthesis strategy. The D-GSH obtained has been nitrosated to give the D-isomer of the bioactive thionitrite, S-nitroso-L-glutathione. The biological activity of both enantiomers of S-nitrosoglutathione has been studied and compared to the activity of the D- and L-isomers of N-acetyl-S-nitrosopenicillamine (SNAP) and S-nitrosocysteine (CysNO).     

Parallel synthesis and pharmacological screening of nonpeptide ligands of the neuropeptide Y receptor subtype Y5.

Several series of low-molecular-mass ligands of the neuropeptide receptor subtype Y5 were prepared using a mixed strategy of synthesis on solid phase and in solution. Collections of single compounds were obtained by an automated parallel procedure which allowed quick variation and investigation of the central spacer moiety, as well as of the aromatic substituents on each side. The strategy of parallel synthesis and screening of partially purified analogs helped to select rapidly potent and selective leads which displayed comparable antagonistic potency against neuropeptide Y activity on the Y5 receptor and better receptor selectivity than the original reference compounds.     

Computation‐Guided Design of LiTaSiO5, a New Lithium Ionic Conductor with Sphene Structure

The development of all‐solid‐state Li‐ion batteries requires solid electrolyte materials with many desired properties, such as ionic conductivity, chemical and electrochemical stability, and mechanical durability. Computation‐guided materials design techniques are advantageous in designing and identifying new solid electrolytes that can simultaneously meet these requirements. In this joint computational and experimental study, a new family of fast lithium ion conductors, namely, LiTaSiO₅ with sphene structure, are successfully identified, synthesized, and demonstrated using a novel computational design strategy. First‐principles computation predicts that Zr‐doped LiTaSiO₅ sphene materials have fast Li diffusion, good phase stability, and poor electronic conductivity, which are ideal for solid electrolytes. Experiments confirm that Zr‐doped LiTaSiO₅ sphene structure indeed exhibits encouraging ionic conductivity. The lithium diffusion mechanisms in this material are also investigated, indicating the sphene materials are 3D conductors with facile 1D diffusion along the [101] direction and additional cross‐channel migration. This study demonstrates a novel design strategy of activating fast Li ionic diffusion in lithium sphenes, a new materials family of superionic conductors.     

A synthetic strategy for ON-resin amino acid specific multiple fatty acid acylation of peptides

Covalent modification with fatty acids is observed in several proteins that play crucial roles in cellular physiology. In this paper, a convenient method for the generation of multiple fatty acylated synthetic peptides is described. Peptides were synthesized using solid phase procedures with fluorenylmethoxycarbonyl a-amino protected amino acids. Acetamidomethyl protected cysteines were employed. The thiol protecting group was selectively deprotected and acylation was carried out on the resin-bound peptides. The strategy described in this report is applicable to any peptide sequence.     

Synthesis and biophysical characterization of G-rich oligonucleotides conjugated with sugar-phosphate tails

A number of 5'-and 3'-glycoconjugates of the oligonucleotide (5')d(TGGGAG)(3') have been synthesized, exploiting fully automated, online phosphoramidite-based solid phase strategy, as potential anti-HIV-1 agents. The thermodynamic stability of the resulting quadruplexes has been investigated by thermal denaturation studies, via a detailed CD Q1 analysis.     

Polymer selection for biphenyl degradation in a solid-liquid two-phase partitioning bioreactor

The commercially available thermoplastic polymer Hytrel was selected as the delivery phase for the hydrophobic model compound biphenyl in a solid-liquid two-phase partitioning bioreactor (TPPB), and 2.9 g biphenyl could successfully be degraded in 1-L TPPBs by a pure culture of the biphenyl-degrading bacterium Burkholderia xenovorans LB400 in 50 h and by a mixed microbial consortium isolated from contaminated soil in 45 h. TPPBs consist of an aqueous cell-containing phase and an immiscible second phase that partitions toxic and/or poorly soluble substrates (in this case biphenyl) on the basis of maintaining a thermodynamic equilibrium. This paper illustrates a rational strategy for selecting a suitable solid polymeric substance for the delivery of the poorly water-soluble model compound biphenyl. The partitioning of biphenyl between the selected polymers and water was analogous to partitioning of solutes between two immiscible liquid phases. The partitioning coefficients varied between 180 for Nylon 6.6 and 11,000 for Desmopan, where the later numerical value is comparable to biphenyl partitioning coefficients between water and organic solvents. Employing a solid delivery phase enabled the utilization of a surfactant-producing microbial mixed culture, which could not be cultivated in liquid-liquid TPPBs and thereby extended the range of biocatalysts that can be employed in TPPBs.