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Stereochemistry of terpene derivatives. Part 7: Novel rigidified amino acids from (+)-3-carene designed as chiral GABA analogues
Abstract
Several novel cyclopropyl-rigidified γ- and δ-amino acids 3–4 have been prepared starting from monoterpene (+)-3-carene 2. These compounds are proposed as chiral analogues of γ-aminobutyric acid (GABA) 1 and are expected to be of interest as potential inhibitors of GABA receptors.
... Within the terpenoids containing an N-OH moiety, effective anticancer (Kahnt et al. 2018) and antimicrobial agents (Hertiani et al. 2010;Grishko et al. 2014) were found. Chemical modifications of monoterpenoids create a possibility of obtaining novel inhibitors of various enzymes (Gajcy et al. 2010). Librowski et al. (2001) described the strong local anaesthetic activity of hydroxyamino carane derivatives. ...
Incorporation of the Beckmann rearrangement into the presented research resulted in the formation of nitrogen-containing terpenoid derivatives originating from naturally occurring compounds. Both starting monoterpenes and obtained derivatives were subjected to estimation of their antibacterial potential. In the presented study, Staphylococcus aureus was the most sensitive to examined compounds. The Minimal Inhibitory Concentration (MIC) experiments performed on S. aureus demonstrated that the (−)-menthone oxime (−)-8 and (+)-pulegone oxime (+)-13 had the best antibacterial activity among the tested derivatives and starting compounds. Their MIC90 value was 100 µg/mL. The obtained derivatives were also evaluated for their inhibitory activity against bacterial urease. Among the tested compounds, three active inhibitors were found – oxime 14 and lactams (−)-15 and 16 limited the activity of Sporosarcina pasteurii urease with Ki values of 174.3 µM, 43.0 µM and 4.6 µM, respectively. To our knowledge, derivative 16 is the most active antiureolytic lactam described to date.
... [2] Anticonvulsant and antidepressant activity of the selected terpene derivatives was also proved in experimental tests in mice. [3] Monoterpenes -as the largest class of plant secondary metabolites -are generally associated with diverse biological activities, including antioxidant, anti-inflammatory and vast antimicrobial properties. They are known as dietary components, pharmaceuticals and insect repellants. ...
In the synthesis performed in this study, derivatives of 4‐tert‐butylcyclohexanone 1 were obtained using typical reactions of organic synthesis. The bioactivity of the selected compounds was evaluated. 1‐(Bromomethyl)‐8‐tert‐butyl‐2‐oxaspiro[4.5]decan‐3‐one (5) was characterized by attractant properties against larvae and a weak feeding deterrent activity against adults of Alphitobius diaperinus Panzer. This bromolactone was a moderate antifeedant towards Myzus persicae Sulzer. In addition, ethyl (4‐tert‐butylcyclohexylidene)acetate (2) and bromolactone 5 displayed antibacterial activity. The strongest bacteriostatic effect was observed against Gram‐positive strains: Bacillus subtilis and Staphylococcus aureus. The bromolactone 5 also limited the growth of Escherichia coli strain.
... Those possessing properties that can be applied in various industries (availability and above all relatively low cost) have increased interest in natural products as starting substrates in organic synthesis. Terpenes and terpenoids are groups of compounds that perfectly meet the conditions of inexpensive and natural synthons, and on many occasions, they enable the production of compounds with wide biological activity (Frackowiak et al. 2006;Gajcy et al. 2010;Kozioł et al. 2014). Terpenoids are often associate with antimicrobial and anticancer properties (Dai et al. 2018), anti-inflammatory characteristics (Shal et al. 2018) or may even act as deterrents towards insects (Devappa et al. 2011). ...
Terpenoid derivatives, which contain a preserved carane system in their structure, exhibit a broad spectrum of biological activities. Among them, we can distinguish insecticides, structures with pharmacological application etc. In the presented paper, the substrate - (–)-cis-caran-trans-4-ol was transformed using the reactions of typical organic synthesis to obtain novel derivatives. Most importantly, bromolactone ((–)-(1R,4R,6S)-2'-(bromomethyl)-4,7,7-trimethylspiro[bicyclo[4.1.0]heptan-3,3'-furan]-5'(4'H)-one) with the preserved carane system was synthesized. This bromolactone was tested for antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer, and peach potato aphid (Myzus persicae). In addition, its moderate antibacterial activity was observed against the Bacillus subtilis strain (with Minimal Inhibitory Concentration of 200 µg/mL).
... The early works of functionalization of terpenes with amine groups were reported by Keim et al. 326 328 and Gajcy et al. 329 proposed the synthesis of amino terpenes in several steps for neurological applications. They presented the possibility of using terpene such as (+)-3-carene and (−)-menthol, as synthons for the preparation of amino acids with predetermined stereogenic centers. ...
Amines are key intermediates in the chemical industry due to their nucleophilic characteristic which confers a high reactivity to them. Thus, they are key monomers for the synthesis of polyamides, polyureas, polyepoxydes, which are all of growing interest in automotive, aerospace, building, or health applications. Despite a growing interest for biobased monomers and polymers, and particularly polyamides, it should be noticed that very few natural amines are available. Actually, there is only chitosan and poly(lysine). In this review we present both fundamental and applied research on the synthesis of biobased primary and secondary amines with current available biobased resources. Their use is described as a building block for material chemistry. Hence, we first recall some background on the synthesis of amines, including the reactivity of amines. Second we focus on the synthesis of biobased amines from all sorts of biomass, from carbohydrate, terpenes, or oleochemical sources. Third, because they need optimization and technological developments, we discuss some examples of their use for the creation of biobased polymers. We conclude with the future of the synthesis of biobased amines and their use in different applications.
... Also, it is well documented that attenuation of GABAergic neurotransmission is involved in the pathophysiology of several CNS disorders in humans, namely anxiety, pain, and epilepsy. It is one of the important targets in the design and discovery of successful antiepileptic drugs (Gajcy et al.; , Loscher et al., 1985 Curtis et al., 1978 ). Until now, aryl and heteroaryl semicarbazones and thiosemicarbazones are very well-established anticonvulsants. ...
A series of (E)-N′-(substituted-benzylidene)isonicotinohydrazide derivatives were synthesized by coupling it with different substituted aldehydes, acetophenone, and benzophenones in presence of absolute ethanol along with catalytic amount of glacial acetic acid. All the synthesized compound were confirmed and characterized by using various spectral technique like IR, 1H NMR, 13C NMR, and mass spectroscopy studies. Anticonvulsant evaluations of all the synthesized compounds were done using various seizures models like maximal electroshock-induced seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) at a dose of 30, 100, and 300 mg/kg body weight and anticonvulsant activity was noted at 0.5 h and 4 h time intervals after the drug administration. Compound 1a (E)-N′-2-benzylidene isonicotinohydrazide, 1g (E)-N′-2-ethoxybenzylidene isonicotinohydrazide, 1k (E)-N′-3-flourobenzylidene isonicotinohydrazide and 3a (E)-N′-diphenylmethylene isonicotinohydrazide showed protection in MES model, which indicates that these compounds have the ability to prevent the spread of seizure at 300 mg/kg dose and showed protection at 0.5 h duration. Compound 3a was also found to be active in scPTZ screen at a dose of 300 mg/kg. In neurotoxicity screen, all the synthesized compounds were found non-toxic except compounds 1n, 2a, and 3b. Further compounds 1a, 1g, 1k, and 3a were also evaluated in the minimal clonic seizure model and exhibited potent anticonvulsant activity with lower neurotoxicity. Among all synthesized derivatives, analogue 3a was found to exhibit protection in MES and scPTZ seizure models. This study proved that isonicotinoyl hydrazides synthesized by condensing isoniazid with various aldehydes and ketones displayed moderate to potent anticonvulsant activity.
Efficient syntheses of six potentially useful optically pure macroheterocycles with ester and dihydrazide fragments were developed from available natural Δ3-carene through intermediate (31R,33S)-32,32-dimethyl-3(1,3)cyclopropyla-5-oxohexanoic acid using in the key steps [2+1]-reactions of the last with di- or triethylene glycol and [1+1]-condensation of the resulting α,ω-diketodiesters with several dicarboxylic acid dihydrazides. The structures of the obtained compounds were confirmed by IR and NMR spectroscopy and LC-MS.
Reduction of the peroxide ozonolysis products of (–)-α-pinene and (+)-3-carene by capric and benzoic acid hydrazides in CH2Cl2 or THF produced diacylhydrazones either pure or mixed with the corresponding ketoacids. The capric acid diacylhydrazone formed primarily in CH2Cl2; benzoic acid diacylhydrazone, in THF. The only reaction products formed in MeOH were the corresponding ketoesters.
This review fills an apparent gap existing in the literature by providing an overview of the readily available terpenes and existing catalytic protocols for preparation of terpene-derived amines. To address the role of solid catalysts in amination of terpenes the same reactions with homogeneous counterparts are also discussed. Such catalysts can be considered as a benchmark, which solid catalysts should match. Although catalytic systems based on transition metal complexes have been developed for synthesis of amines to a larger extent, there is an apparent need to reduce the production costs. Subsequently, homogenous systems based on cheaper metals operating by nucleophilic substitution (e.g., Ni, Co, Cu, Fe) with a possibility of easy recycling, as well as metal nanoparticles (e.g., Pd, Au) supported on amphoteric oxides should be developed. These catalysts will allow synthesis of amine derivatives of terpenes which have a broad range of applications as specialty chemicals (e.g., pesticides, surfactants, etc.) and pharmaceuticals. The review will be useful in selection and design of appropriate solid materials with tailored properties as efficient catalysts for amination of terpenes.
This review outlines the most recent papers describing the stereoselective synthesis of γ-amino acids. In this update, the γ-amino acids have been classified according to the type of compounds, position and number of substituents, and depending on the type of substrate, acyclic, carbocyclic or azacyclic derivatives, following in the first case an order related to the strategy used, whereas in the second and third cases the classification is based on the ring size.
A simple synthetic procedure for the preparation of mono-N-tosylated-1,2-diamines derived from (+)-3-carene is described. (+)-3-Carene is transformed into the corresponding N-tosylaziridine derivative using chloramine-T trihydrate. Subsequent ring opening with sodium azide followed by reduction of the azide function gives the optically pure mono-N-tosylated-1,2-diamine. This ligand is effective in asymmetric transfer hydrogenations of aromatic ketones. It can also be transformed into other chiral ligands by alkylation of the amino group for application in the addition of diethylzinc to benzaldehydes.
Starting from a chiral methylenecyclopropane building block, readily obtained by enzymatic desymmetrization of a meso-diol, two types of methylenecyclopropane analogues of nucleosides were synthesized. The first type of nucleosides was obtained from the direct coupling of the chiral building block with 6-chloropurine under Mitsunobu reaction conditions followed by the functionalization of the purine base. The second type of nucleosides featured a Curtius rearrangement as the key step and the uracil heterocycle was then constructed by a linear methodology. These derivatives were evaluated as potential agents against important viral pathogens. None of the new compounds had significant antiviral activity at a concentration of 100 g/mL, which was the highest concentration tested.
The syntheses of the marine sponge-derived γ-amino carboxylic acid dysibetaine CPa and five analogs in their racemic forms were successfully performed by taking advantage of an electron-withdrawing N-(4-nitrophenyl) group in the cyclopropanation reaction, the reductive ring opening of an imide, and the ethanolysis of an N-Boc-protected imide.
From a high-throughput screening campaign aiming at the identification of novel S1P1 receptor agonists, the pyrazole derivative 2 emerged as a hit structure. Medicinal chemistry efforts focused not only on improving the potency of the compound but in particular also on resolving its inherent instability issue. This led to the discovery of novel bicyclo[3.1.0]hexane fused thiophene derivatives. Compounds with high affinity and selectivity for S1P1 efficiently reducing the blood lymphocyte count in the rat were identified. For instance, compound 85 showed EC50 values of 7 and 2880 nM on S1P1 and S1P3, respectively, had favorable pharmacokinetic properties in rat and dog, distributed well into brain tissue, and efficiently and dose dependently reduced the blood lymphocyte count in the rat. After oral administration to spontaneously hypertensive rats, the S1P1 selective compound 85 showed no effect on mean arterial blood pressure and affected the heart rate during the wake phase of the animals only.
This compendium focuses on functionalised sugar amino acids (SAAs) and their 3- to 6-membered nitrogen heterocyclic and carbocyclic analogues. The main benefit of using SAAs and their related nitrogen and carbon congeners in the production of peptidomimetics and glycomimetics is that their properties can be readily altered via modification of their ring size, chemical manipulation of their numerous functional groups and fine-tuning of the stereochemical arrangement of their ring substituents. These building blocks provide access to hydrophilic and hydrophobic peptide isosteres whose physical properties allow entry to a region of chemotherapeutic space which is still under-explored by medicinal chemists. These building blocks are also important in providing amino acids whose inherent conformational bias leads to predisposition to secondary structure upon oligomerisation in relatively short sequences. These foldamers, particularly those containing ω-amino acids, provide an additional opportunity to expand access to the control of structures by artificial peptides. The synthesis and biological evaluation of these building blocks in glycomimetics and peptidomimetics systems keep expanding the reach of the glycosciences to the medical sciences, provide a greater outlook onto the wide range of cellular functions of saccharides and their derivatives involved and greater insight into the nature of oligosaccharide and protein folding.
Michael addition of dibenzylamine to (−)- and (+)-tert-butyl myrtenate, (−)-2 and (+)-2, derived from (−)- and (+)-myrtenal, furnished monoterpene-based β-amino acid derivatives in highly stereospecific reactions. The resultant amino esters (−)-3 and (+)-3 were transformed to unsubstituted, mono- and disubstituted and Fmoc-protected amino acids (−)-6-11 and (+)-6-11, which are promising building blocks for the synthesis of β-peptides and 1,3-heterocycles. The microwave-assisted conjugate addition of nitromethane to α,β-unsaturated esters (−)-12 and (+)-12 likewise resulted in nitro esters (−)-13 and (+)-13 in highly stereospecific reactions. Compounds (−)-13 and (+)-13 were successfully transformed into γ-amino acids (−)-16 and (+)-16 in two steps.
The Kulinkovich-de Meijere reaction between an unsaturated Grignard reagent and a chiral amide takes place with a high trans stereoselectivity and provides a convenient access to non-racemic trans cyclopropylamines. These compounds are transformed in four steps into the corresponding N-protected β,γ-methano-GABA derivatives, which are obtained for the first time in enantiomerically pure form. The corresponding transformations of the cis cyclopropylamine adducts are also described.
A few derivatives of natural, bicyclic monoterpenes, which are propranolol analogs, were synthetized. Those compounds were studied pharmacologically in order to determine their toxicity, antiarrhythmic activity in selected experimental models of arrhythmia, the local anesthetic effect and influence on the cardiovascular system. The tested compounds showed a less potent or similar toxicity towards reference drugs, were devoid of an antiarrhythmic activity in the model of barium arrhythmia, yet some of them (compounds 9 and 12) increased the arrhythmogenic dose of strophanthin. All the compounds studied had a local anesthetic effect stronger than lidocaine in infiltration anesthesia, and compound 8--also in surface anesthesia.
Our previously conducted pharmacological screening led as to the discovery of the strong local anesthetic activity of the compound designated as KP-23. Earlier crystallographic studies revealed that the compound KP-23 crystallized in diastereoisomeric form in lowest symmetry. The aim of these comparative investigations was to evaluate anesthetic activity of KP-23 and its R,S-diastereoisomers, which were synthesized at the Institute of Organic Chemistry, Biochemistry and Biotechnology, Wroclaw University of Technology.
In the mature brain, GABA (gamma-aminobutyric acid) functions primarily as an inhibitory neurotransmitter. But it can also act as a trophic factor during nervous system development to influence events such as proliferation, migration, differentiation, synapse maturation and cell death. GABA mediates these processes by the activation of traditional ionotropic and metabotropic receptors, and probably by both synaptic and non-synaptic mechanisms. However, the functional properties of GABA receptor signalling in the immature brain are significantly different from, and in some ways opposite to, those found in the adult brain. The unique features of the early-appearing GABA signalling systems might help to explain how GABA acts as a developmental signal.
Temporal lobe epilepsy (TLE), Parkinson's disease (PD) and Huntington's disease (HD) are neurodegenerative disorders that involve disruptions in gamma-amino butyric acid (GABA) signalling. GABA is the major inhibitory neurotransmitter in the central nervous system (CNS). TLE seizures reflect excess excitation, which may result from local inhibitory circuit dysfunction. PD devastates the input to striatal GABAergic neurones and HD destroys striatal GABAergic neurones. Controlling GABA delivery to specific brain areas should benefit each of these diseases. The molecules responsible for GABA release and signalling are ideal targets for new therapies. In this paper, we discuss the role of GABA in the circuitry affected by each of these diseases and suggest potential sites for intervention. GABA is unique among neurotransmitters because it can be synthesised by either of two related enzymes. Intracellular GABA is found throughout the cytosol and in synaptic vesicles. GABA can be released either through exocytosis, or via the plasma membrane transporter. The synthesising enzyme probably determines the intracellular location and hence the mechanism for GABA release. Directing GABA synthesis, degradation, transport or receptors can control GABA signalling. We propose that new drugs and devices aimed at GABA synthesis, release and binding will offer novel and highly effective treatments for neurodegenerative diseases.
γ-Amino acids have attracted considerable attention as biologically active compounds in the central nervous system (CNS) of mammals. Over the last few years, significant interest in the stereoselective synthesis and practical application of linear and cyclic chiral γ-amino acids in the synthesis and design of α,β- and β,γ-hybrid peptides with definite secondary structures and design of nanotubes has been reported, thus demonstrating the theoretical interest and the practical importance of γ-amino acids. An overview of synthetic approaches to linear and cyclic chiral γ-amino acids and derivatives is presented. Data on the practical applications of γ-amino acids are also discussed.
We describe a facile synthetic method of carbamate- and urea-linked glycoconjugates using sugar carboxylic acids by the modified Curtius rearrangement. This reaction is a simple one-pot procedure, and various nucleophiles including tertiary alcohols can be utilized to afford desired compounds in moderate to high yields. And the stereospecific synthesis of the anomeric isomers is achieved using the corresponding two stereoisomers of glycosyl carboxylic acid. (c) 2006 Elsevier Ltd. All rights reserved.
Starting from (+)-3-carene 1, several chiral fragrant compounds with the bicyclo[3.1.0]hexane system were synthesized. These compounds were used as substrates for the biotransformation with lipases as biocatalysts. Pure diastereoisomers were obtained and their absolute configuration was confirmed by X-ray crystallography. The olfactory properties of new compounds were determined.
Unlabelled:
Reduced brain gamma-amino-butyric acid (GABA) participates in the pathogenesis of schizophrenia. GABA scarcely penetrates the brain. We evaluated the pharmacological properties of BL-1020, a novel GABA ester of perphenazine. Oral BL-1020 or perphenazine were assessed in acute and subchronic schizophrenia rat models. Catalepsy, serum prolactin, receptor binding profile and cortical (PFC), hippocampal (Hip) and dopamine (DA) levels were determined. Radioactive [14C] labeled BL-1020 was used for pharmacokinetics (PK). Acute and subchronic treatment with BL-1020 antagonized amphetamine-induced hyperactivity, with significantly lower catalepsy and sedation compared to equimolar perphenazine. At the same time, BL-1020 increased DA release in the PFC and Hip. BL-1020 and perphenazine stimulated prolactin secretion equally. BL-1020 displayed strong DA and serotonin (5HT) receptor inhibition (D(2L)K(iz)=0.066 nM, D(2S)K(i)=0.062 nM, 5-HT(2A)K(i)=0.21 nM). PK data revealed that BL-1020 penetrated the brain.
Conclusions:
The advantages of BL-1020 for treatment of schizophrenia stem from its being a DA/5HT antagonist and a GABAergic agonist that releases cortical DA and antagonizes amphetamine-induced hyperactivity with reduced catalepsy and sedation.
GABA transmission plays a key role in controlling seizure activity. The precise nature of its effect depends on the particular location in the brain and the pathway involved. Animal studies have helped to define specific brain regions such as the substantia nigra and area tempestas that are critical in controlling seizure activity. Antiepileptic drugs such as vigabatrin [gamma vinyl GABA (GVG)], a drug rationally developed to treat resistant epilepsy, can enhance GABA transmission in these regions and may thereby afford seizure protection.
In order to investigate the sequence and pattern of neurodegeneration in Huntington's disease, the distribution and density of cannabinoid CB1, dopamine D1 and D2, adenosine A2a and GABAA receptor changes were studied in the basal ganglia in early (grade 0), intermediate (grades 1, 2) and advanced (grade 3) neuropathological grades of Huntington's disease. The results showed a sequential pattern of receptor changes in the basal ganglia with increasing neuropathological grades of Huntington's disease. First, the very early stages of the disease (grade 0) were characterized by a major loss of cannabinoid CB1, dopamine D2 and adenosine A2a receptor binding in the caudate nucleus, putamen and globus pallidus externus and an increase in GABAA receptor binding in the globus pallidus externus. Second, intermediate neuropathological grades (grades 1, 2) showed a further marked decrease of CB1 receptor binding in the caudate nucleus and putamen; this was associated with a loss of D1 receptors in the caudate nucleus and putamen and a loss of both CB1 and D1 receptors in the substantia nigra. Finally, advanced grades of Huntington's disease showed an almost total loss of CB1 receptors and the further depletion of D1 receptors in the caudate nucleus, putamen and globus pallidus internus, and an increase in GABAA receptor binding in the globus pallidus internus.
A new class of self-assembling peptides based on cyclic peptides made of alternating 3-aminocyclohexanecarboxylic acid (gamma-Acc) and alpha-amino acids is described. The studied cylindrical assemblies are models for a new class of self-assembling peptide nanotubes (SPN) that present the particular property of having the C2 methylene group pointing toward the lumen of the cavity, modifying the properties of the inner surface of the assembly.
The transport of gamma-aminobutyric (GABA) limits the overspill from the synaptic cleft and serves to maintain a constant extracellular level of GABA. Two transporters, GABA transporter-1 (GAT-1) and GAT-3, are the most likely candidates for regulating GABA transport in the brain. Drugs acting either selectively or nonselectively at GATs exert distinct anticonvulsant effects, presumably because of distinct regions of action. Here I shall give a brief review of the localization and physiology of GATs and describe effects of selective and nonselective inhibitors thereof in different animal models of epilepsy.
[reaction: see text] The multicomponent coupling of alkenylzirconocenes with N-diphenylphosphinoyl imines provides rapid access to functionalized C-cyclopropylalkylamides which have been readily transformed into alpha,beta-cyclopropyl-gamma-amino acids. These novel scaffolds are thus accessible in ca. 8 steps from commercially available alkynes.
The synthesis of cis-gamma-amino-l-proline oligomers functionalized at the proline alpha-amine with several groups that mimic the side chains of natural amino acids, including alanine, leucine, and phenylalanine, is herein described. These gamma-peptides enter into different cell lines (COS-1 and HeLa) via an endocytic mechanism. The ability of these compounds to be taken up into cells was studied at 37 degrees C and 4 degrees C by plate fluorimetry, flow cytometry, and confocal microscopy. In addition to their capacity for cellular uptake, these unnatural short length oligomers offer advantages over the well-known penetrating TAT peptide, such as being less toxic than TAT and protease resistance.
[structure: see text] A complete overview on the alternative and competitive helices in vinylogous gamma-peptides is given, which was obtained on the basis of a systematic conformational analysis at various levels of ab initio MO theory (HF/6-31G*, DFT/B3LYP/6-31G*, PCM/HF/6-31G*). Contrary to the parent gamma-peptides, there is a strict control of helix formation by the configuration of the double bond between the C(alpha) and C(beta) atoms of the monomer constituents. (E)-Double bonds favor helices with larger pseudocycles beginning with 14- up to 27-membered hydrogen-bonded rings, whereas the (Z)-configuration of the double bonds supports a distinct preference of helices with smaller seven- and nine-membered pseudocycles showing interactions between nearest-neighbor peptide bonds. The rather stable helices of the (E)-vinylogous peptides with 22-, 24-, and 27-membered hydrogen-bonded pseudocycles have inner diameters large enough to let molecules or ions pass. Thus, they could be interesting model compounds for the design of membrane channels and monomolecular nanotubes. Since (E)- and (Z)-vinylogous gamma-amino acids and their oligomers are synthetically accessible, our study may stimulate structure research in this novel field of foldamers.
(Chemical Equation Presented) Nine is the number: Novel C 9-hydrogen-bonded structures (in which the hydrogen bonds enclose a ring of nine atoms) are observed in protected di- and tetrapeptides formed by the γ-amino acid residue gabapentin. The structures reveal new families of C9 helices and ribbons (see structure) in γ-polypeptides.
Cyclic peptides can dimerize through β-sheet-like hydrogen bonding. Heterodimerization is favored over homodimerization, which creates interesting combinatorial possibilities without detriment to the functionalization of amino acid side chains. These dimers represent a new class of self-assembling peptide nanotubes in which the hydrophobicity of the internal cavity (see picture) can be controlled. (Graph Presented).
Alpha,gamma- and beta,gamma-hybrid peptides, which are composed of two different homologous amino acid constituents in alternate order, are suggested as novel classes of peptide foldamers. On the basis of a systematic conformational search employing the methods of ab initio MO theory, the possibilities for the formation of periodic secondary structures in these systems are described. The conformational analysis provides a great number of helix conformers widely differing in energy, which can be arranged into three groups: (i) helices with all hydrogen bonds formed in forward direction along the sequence, (ii) helices with all hydrogen bonds in backward direction, and (iii) helices with alternate hydrogen-bond directions (mixed or beta-helices). Most stable are representatives of beta-helices, but their stability decreases considerably in more polar environments in comparison to helix conformers from the other two classes. There is a great similarity between the overall topology of the most stable hybrid peptide helices and typical helices of peptides which are exclusively composed of a single type of homologous amino acids. Thus, the helices of the beta,gamma-hybrid peptides mimic perfectly those of the native alpha-peptides as, for instance, the well-known alpha-helix, whereas the most stable helix conformers of alpha,gamma-hybrid peptides correspond well to the overall structure of beta-peptide helices. The two suggested novel hybrid peptide classes expand considerably the pool of peptide foldamers and may be promising tools in peptide design and in material sciences.
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Polish Patent Application P390969
- S Lochynski
- K Gajcy
Polish Patent Application P390968
- S Lochynski
- K Gajcy
- B Frackowiak-Wojtasek