Asymmetric Synthesis of α-Amino Phosphonic Acids using Stable Imino Phosphonate as a Universal Precursor

A practical method for synthesizing chiral α-amino phosphonic acid derivatives was developed. Readily available and stable N-o-nitrophenylsulfenyl (Nps) imino phosphonate was utilized as a substrate for a highly enantioselective Friedel–Crafts-type addition of indole or pyrrole nucleophiles catalyzed by chiral phosphoric acid. The resulting adduct was easily converted into N-9-fluorenylmethyloxycarbonyl (Fmoc) amino phosphonic acid, which is useful for synthesizing peptides containing an amino phosphonic acid.     

Synthetic Methods of Phosphonopeptides

Phosphonopeptides are phosphorus analogues of peptides and have been widely applied as enzyme inhibitors and antigens to induce catalytic antibodies. Phosphonopeptides generally contain one aminoalkylphosphonic acid residue and include phosphonopeptides with C-terminal aminoalkylphosphonic acids and phosphonopeptides with a phosphonamidate bond. The phosphonamidate bond in the phosphonopeptides is generally formed via phosphonylation with phosphonochloridates, condensation with coupling reagents and enzymes, and phosphinylation followed by oxidation. Pseudo four-component condensation reaction of amides, aldehydes, alkyl dichlorophosphites, and amino/peptide esters is an alternative, convergent, and efficient strategy for synthesis of phosphonopeptides through simultaneous construction of aminoalkylphosphonic acids and formation of the phosphonamidate bond. This review focuses on the synthetic methods of phosphonopeptides containing a phosphonamidate bond.     

Synthesen der Phosphono- bzw. Phosphino-Analoga des Pantothensäure-ethylesters und des Phosphono-Analogons des Pantetheins

Syntheses of Phosphonic- and Phosphinic Analogues of Pantothenic Acid Ethyl Ester and of the Phosphonic Analogue of Pantetheine The replacement of amino acids in peptides by phosphono-analogous (aminoalkyl)phosphonic acids 1 , (2-aminoethyl)phosphonic acid ( 2 ) and substituted derivatives has been an important aspect of peptides research in the last years. In pantothenic acid ( 3 ), there is a peptide linkage between (2R)-2,4-dihydroxy-3,3-dimethylbutyric acid and the amino group of β-alanine, and in pantetheine ( 4 ), there is a second peptide linkage between the β-alanine and cysteamine. The synthesis of phosphono and phosphino analogues of pantothenic acid ethyl ester, where the β-alanine is replaced by the diethyl ester of (2-aminoethyl)phosphonic acid and the ethyl ester of (2-aminoethyl)methylphosphonic acid, respectively, and the syntheses of the phosphono analogue of pantetheine, where the β-alanine is replaced by (2-aminoethyl)phosphonic acid, are described.     

Catalytic Asymmetric 1,2‐Addition of α‐Isothiocyanato Phosphonates: Synthesis of Chiral β‐Hydroxy‐ or β‐Amino‐Substituted α‐Amino Phosphonic Acid Derivatives

α‐Amino phosphonic acid derivatives are considered to be the most important structural analogues of α‐amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2‐addition reactions of α‐isothiocyanato phosphonate were developed. Through these processes, derivatives of β‐hydroxy‐α‐amino phosphonic acid and α,β‐diamino phosphonic acid, as well as highly functionalized phosphonate‐substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α‐phosphonic acid derivatives.     

Synthesis of Enantiomeric Aminophosphonic Acids and Peptides

Abstract

Synthesis of enantiomeric amino phosphonic acids APA is described by using chiral auxiliary reagent or enzymatic resolution of racemic mixtures of APA phenacyl derivatives. Peptides with APA residue were obtained by application of trimethylsilyl derivatives or condensation in the presence of enzyme-papain     

An Analysis of the Enzyme-Inhibitor Binding Interactions for Phosphonic Acid Transition State Analogs of Thermolys in

Abstract

Potent inhibitors of the zinc endopeptidase thermolysin are produced on replacement of the scissile peptide linkage with phosphonamidate or phosphonate ester moieties. These inhibitors have been shown to be transition state analogs, and a comparison between the esters and amidates reveals the intrinsic binding energy due to a specific hydrogen bonding interaction. Incorporation of an α-substituted phosphonic acid analog leads to slow-binding behavior on the part of the inhibitors, which is attributed to expulsion of a specific water molecule from the active site.     

Novel synthetic method of phosphonamidate peptides and its application in peptide sequencing via multistage mass spectrometry

Phosphonamidate peptides were prepared in good yields by reaction of ethoxy(phenyl)phosphinate with free peptides in a mixed solution of H2O, C2H5OH, Et3N and CCl4 at room temp.; their in situ electrospray ionization mass spectra exhibited high sensitivity compared with the free peptides, and sequential loss of amino acid residues of the sodiated phosphonamidate peptides from the C-terminus was found in multistage ESI mass spectrometry. The results show that N-phosphonyl derivatization combined with multistage ESI-MS is a powerful method for peptide sequencing.     

Determination of amine-containing phosphonic acids and amino acids as dansyl derivatives

Conditions are selected for the analytical separation of (N-phosphonomethyl glycine), products of its microbiological conversion, glutamic acid, and alanine as dansyl derivatives using reversed-phase HPLC: column (250 × 4.6 mm) ReproSil-PAH EPA; mobile phase, methanol + 20 mM CH₃COONa (pH 5.1) (20: 80); rate of mobile phase, 1 mL/min; working detector wavelength, 330 nm. The duration of separation is 35 min. The lower limits of the analytical range (in ng) for dansyl derivatives are as follows: glyphosate, 8.2; aminomethyl phosphonic acid, 24.2; glutamic acid, 9.4; alanine, 12.6: glycine, 17.7; and sarcosine, 19.3. The TLC study of dansyl derivatives of amino acids was performed on sorbfil plates PTSH-P-V using two-dimensional chromatography in the systems ethyl acetate-isopropanol-24% aqueous ammonia (45: 35: 20) in the first direction and chloroform-methanol-acetic acid (25: 5: 1) in the second one. For determining phosphonic acids (glyphosate and aminomethyl phosphonic acid), a version of one-dimensional chromatography with the sequential use of two systems, chloroform-methanol-acetic acid (25: 5: 0.2) and ethanol-24% aqueous ammonia (7: 3), was proposed.     

The Synthesis of Cystine Peptides by Iodine Oxidation of S-Trityl-cysteine and S-Acetamidomethyl-cysteine Peptides

Previously reported studies of the iodine oxidation of S-trityl-cysteine peptides and S-acetamidomethyl-cysteine peptides, leading directly to cystine peptides, have been extended. Detailed investigations have been made of the reactivities of the S-trityl and the S-acetamidomethyl group towards iodine in various solvents. In chloroform, methylene chloride, trifluoroethanol, and hexafluoroisopropyl alcohol the differences in the reaction rates of the two groups have been found to be extremely large, allowing the selective conversion of the tritylthio groups to disulfides in the presence of the S-acetamidomethyl derivatives. In a second group of solvents, consisting of methanol, acetic acid, dioxane, and mixtures of these solvents with water, simultaneous iodine oxidation of S-trityl- and S-acetamidomethyl-cysteine peptides leads to a preferential combination of these two residues, resulting in predominantly asymmetrical cystine derivatives. - The suitability of the two sulfur-protecting groups in the synthesis of cyclic cystine peptides has been assessed. - Possible reaction mechanisms are discussed. - The scope and limitations of iodine oxidation in peptide synthesis have been studied. The applicability of the method has been demonstrated in the preparation of the open-chain asymmetrical cystine peptide 5 , the protected somatostatin derivative 17 , and the A(1–13) segment 19 of human insulin, previously employed in the total synthesis of this hormone.     

Aminophosphonic and aminophosphinic acid analogues of aspartic acid

4-Oxoazetidin-2-ylphosphonates and phosphinates, obtained from Arbusov reactions of 4-acetoxyazetidin-2-one and 4α-acetoxy-3β-phthalimido-2-one with a variety of phosphites and phosphonites, were hyrdolysed to β-phosphono- and β-phosphino β-alanine (phosphono- and phosphinoaspartic acid) derivatives. In model studies for their incorporation in peptides, conditions for the selective removal of protecting groups for carboxylic acids, phosphonic and phosphinic acids, and amines, in derived di- and tri-peptides were investigated. Alanyl and alanyl alanyl peptide incorporation into bacteria was studied.     

Cyclic Peptides as Inhibitors of Amyloid Fibrillation

Many neurodegenerative diseases, like Parkinson’s, Alzheimer’s, or Huntington’s disease, occur as a result of amyloid protein fibril formation and cell death induced by this process. Cyclic peptides (CPs) and their derivatives form a new class of powerful inhibitors that prevent amyloid fibrillation and decrease the cytotoxicity of aggregates. The strategies for designing CPs are described, with respect to their amino acid sequence and/or conformational similarity to amyloid fibrils. The implications of CPs for the study and possible treatment of amyloid‐related diseases are discussed.     

Bifunctional Adhesion Promoter for Grafting Polypyrrole Films on Metal/Metal Oxide Surfaces

A new class of pyrrole derivatives, ω-[(3-phenyl) pyrrol-1-yl] alkyl phosphonic acids with long chains of 10 and 12 carbon atoms were synthesised to graft polypyrrole layers on metal/metal oxide surfaces. These compounds are bifunctional containing two reactive moieties, pyrrole as the polymerisable group and phosphonic acid as the anchoring group. Contact angle measurements and X-ray photoelectron spectroscopy (XPS) confirmed adsorption with phosphonic acid group attached to the surface. Surface plasmon resonance (SPR) spectroscopy indicated that adsorption starts in seconds and is completed in few hours. Adsorption is followed by surface induced polymerisation with further monomer. We obtained dense and homogeneous polypyrrole films, which were characterised for their morphology and thickness by atomic force microscopy (AFM). The derivatives form a strongly bonded composite of metal with polymer.     

Iron-Catalyzed Biomimetic Dimerization of Tryptophan-Containing Peptides

Biomimetic oxidative dimerization of tryptophan derivatives in aqueous media with oxygen as a bulk oxidant catalyzed by an iron octacarboxy phthalocyanine complex was established. The discovery of the extremely active iron catalyst enables aerobic enzyme-mimetic oxidation to be performed in a flask. This method was applicable to the oxidative dimerization of a wide range of tryptophan derivatives, including various dipeptides and oligopeptides, with remarkable functional-group tolerance without the protection of the amino acid residues. Furthermore, oxidative dimerization of tryptophan derivatives bearing dioxopiperazine units enabled the convergent total synthesis of five natural pyrroloindole compounds and unnatural congeners. The established chemical method provides facile access to a broad range of dimerized peptides with a unique scaffold to link two turn structures, which will serve as a powerful tool to create new small- and medium-sized-molecules as drug candidates.     

HPLC Separation of Geometric Isomers of Carbamyl Peptides

Abstract

Carbamylated peptides that were studied showed much improved resolution on C-18 reversed phase HPLC columns compared to the parent peptides. A number of dipeptides were carbamylated with ethyl-, n-propyl- or isopropyl isocyanates. The three carbamyl derivatives of each dipeptide could easily be resolved. Carbamylated dipeptides with reversed amino acid sequences were also easily separated. Methionine-enkephalin, leucine-enkephalin, Angiotensins I, II and III and substance P were carbamylated with isocyanates derived from certain carcinostatic 2-chloroethyl nitrosoureas. 1-(2-Chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), 1-(2-chloroethyl)-3-(cis-4-hydroxycyclohexyl)-1-nitrosourea (cis-4-hydroxy-CCNU) and 1-(2-chloroethyl)-3-(trans-4-hydroxycyclohexy1)-1-nitroso urea (trans-4-hydroxy-CCNU) gave carbamylated derivatives of each peptide and each mixture of derivatives from a single parent peptide could be resolved. Conditions were found in each case whereby baseline resolution of the corresponding cis-4- and trans-4-hydroxycyclohexylcarbamyl peptides was attained. Cyclohexyl-carbamyl peptides were easily separated from the corresponding peptides from hydroxy-CCNUs. Potential applications are discussed. carbamylation in the expression of antitumor activity or toxicity to normal tissues is still not very clear. A number of DNA polymerases (10, 11), DNA ligase (12), glutathione reductase (13), Serine proteases (14, 15) and tubulin polymerization (16) have been shown to be inhibited by carbamylation by nitrosoureas or isocyanates.

The question of whether carbamylation by CENUs and their metabolites is selective to certain enzymes is an important one because nitrosoureas such as CCNU and Methyl-CCNU are converted to antitumor-active metabolites (8, 17, 18). If it is found that the individual metabolites target different proteins, it could have important applications in chemotherapy and drug design.

In order to determine whether such selectivity of carbamylation exists, it was required that analytical methodology be developed that would permit separation of peptides with the same sequence but with different carbamyl groups. These studies offer hope that if peptides with up to 11 aminoacids are carbamylated by CCNU or the 4-hydroxy-CCNUs, one may be able to separate them by HPLC. This limit may be extended if one need only separate cyclohexyl carbamyl peptides from mixtures of geometric and positional isomers of hydroxycyclohexyl carbamyl peptides as might occur in the cell.     

Modulating Protein–Protein Interactions by Cyclic and Macrocyclic Peptides. Prominent Strategies and Examples

Cyclic and macrocyclic peptides constitute advanced molecules for modulating protein–protein interactions (PPIs). Although still peptide derivatives, they are metabolically more stable than linear counterparts, and should have a lower degree of flexibility, with more defined secondary structure conformations that can be adapted to imitate protein interfaces. In this review, we analyze recent progress on the main methods to access cyclic/macrocyclic peptide derivatives, with emphasis in a few selected examples designed to interfere within PPIs. These types of peptides can be from natural origin, or prepared by biochemical or synthetic methodologies, and their design could be aided by computational approaches. Some advances to facilitate the permeability of these quite big molecules by conjugation with cell penetrating peptides, and the incorporation of β-amino acid and peptoid structures to improve metabolic stability, are also commented. It is predicted that this field of research could have an important future mission, running in parallel to the discovery of new, relevant PPIs involved in pathological processes.     

Novel protective coatings for steel based on a combination of self-assembled monolayers and conducting polymers

Investigations for a new primer system for iron or low alloyed steel have led to first results. Several special phosphonic acids with thiophene derivatives as head groups have been synthesized. They form stable self-assembled monolayers (SAMs) on passivated iron by dipping the substrates into aqueous phosphonic acid solutions. SAM formation was validated by current potential curves and also by contact angle measurements, which showed an intensive hydrophobisation of the iron surface after the dipping process. Finally cyclovoltammetric (CV) experiments after SAM formation indicated the successful polymerisation of the immobilised thiophene derivatives.     

Light-Driven Diselenide Metathesis in Peptides

Peptides containing selenocysteine moieties are susceptible to non-catalytic reactions of diselenide bonds metathesis induced by visible light. In contrast to previously reported radical metathesis of disulfide bridges in cysteine derivatives, this newly developed reaction is fast and clean, and proceeds without decomposition of peptides and without formation of side products. The diselenide bond in peptides was reported in literature to be more stable than the disulfide one and also less susceptible to metathesis induced by thiols and reducing reagents. We demonstrated that visible light induces fast metathesis of Se−Se bonds in peptides. This reaction is important for the folding of peptides containing selenocysteine residues and may find application in designing dynamic combinatorial libraries of peptides responsive to external influence.     

Antibacterial Activity of Peptides Related to Alafosfalin. The Effect of Varying the Aminophosphonate Fragment

Abstract

A series of 32 dipeptides containing N-terminal alanine or leu-cine and a variety of racemic 1-aminoalkanephosphonic acids vere prepared by standard procedures and tested for growth inhibition of six bacterial species (Escherichia coli, Klebsiella aerogenes, Serratia mercescens, Staphylococcus aureus, Streptococcus faeca-lis and Bacillus subtilis). The aminophosphonate residues were racemic and included Va1P, LeuP, ProP, PheP, α-methyl-AlaP, Glu-α-P, O-methyl-DOPAP, cyclohexane-1-amino-1-phosphonic acid, t-LeuP, O-acetyl-SerP, and GlyP derivatives RCH(NH₂)PO₃H₂ where R=cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and adaman-tyl. N-Ala and N-Leu peptides of racemic AlaP were used as positive control. MIC and IC₅₀ values indicate that the peptides containing 4-amino-4-phosphonobutyric acid (Glu-α-P) and α-methyl-AlaP are potent antibiotics, comparable in activity with LeuAlaP and AlaAlaP (Alafosfalin). Weak activity was observed for peptides of ProP, LeuP, ValP, PheP, cyclohexane-1-amino-1-phosphonic acid and 1-aminocyclopentylmethanephosphonic acid. While the activity of the α-methyl-AlaP peptides may be explained by inhibition of alanine racemase, the mechanism of action of the Glu-α-P peptides remains unknown.     

氨基酸、多肽的环糊精化学

本文着重介绍了氨基酸、多肽－环糊精连接物的合成,分子识别和自组装,对环糊精及其衍生物与氨基酸、多肽的包合行为,异构体识别和仿酶合成作了简要概述。     

Phospha-Pharmaca - Antibacterial and Virucidic Compounds

Abstract

Synthetic, antibacterial, and antiviral aspects of the P-glutamic acid type compounds, of phosphonic acids, phospha -peptides, and of phosphorus derivatives of the formic acid are considered.