Bicyclic pyridones as potent, efficacious and orally bioavailable thrombin inhibitors

A new class of conformationally constrained thrombin inhibitors is described. These compounds contain a unique bicyclic pyridone scaffold which serves as a P3P2 dipeptide surrogate. The synthesis and antithrombotic activity of these inhibitors is reported.     

Sugar amino acid based peptide epoxyketones as potential proteasome inhibitors

This paper describes the synthesis and biological evaluation of nine epoxomicin-derived sugar amino acid containing peptide epoxyketones. The title compounds are assembled from six sugar amino acid dipeptide isosteres and are synthesized using solution-phase peptide synthesis protocols. Although neither of the compounds displays inhibitory activity towards any of the proteasome active sites, our approach holds promise towards the development of structurally new proteasome inhibitors. It is likely that the central sugar amino acid dipeptide isoster needs to be designed such that it closely resemble dipeptides at position P2 and P3 in proteasome substrates inhibitors, such as the Thr-Ile dipeptide present in the lead compound, epoxomicin.     

Successive cleavage of N-terminal Arg1--Pro2 and Lys3-Pro4 from substance P but no release of Arg1-Pro2 from bradykinin, by X-Pro dipeptidyl-aminopeptidase

X-Pro dipeptidyl-aminopeptidase (EC 3.4.14.1) purified homogeneously from the human submaxillary gland was proved to hydrolyze N-terminal dipeptide Arg1-Pro2 and subsequent dipeptide Lys3-Pro4 from substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-gly-Leu-Met-NH2). Km and V values of hydrolysis of substance P were 2.0 mM and 3.6 mumol/min per mg protein, respectively. In contrast, the N-terminal Arg-Pro of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) was not cleaved by the enzyme.     

Classification of protein sequences by their dipeptide composition

A simple approach to scan quickly a large protein sequence databasefor homology is described. The approach used is strictly dependenton the database organization. A database has been compiled inwhich protein sequences are grouped into families of closelyrelated proteins, each family being characterized by its averagedipeptide composition. A new entry in the database can be allocatedin a family by comparing its dipeptide composition with theaverage dipeptide composition of the families.     

Synthesis of some 3-hydroxynaphthalene-2-carbonylamino acid and dipeptide derivatives

Synthesis of a series of 3-hydroxynaphthalene-2-carbonylamino acid methyl esters (II-XI) and some of their corresponding hydrazides (XII-XXI), dipeptide methyl esters (XXII-XXXV) and dipeptide hydrazides (XXXVI-XXXIX) is described. 3-Hydroxynaphthalene-2-CO-L-Tyr-N2H3 (XX) and the corresponding L-Val-L-Ala-N2H3 (XXXVI) were found to be active against a number of micro-organisms.     

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.     

An improved procedure for the synthesis of branched polyethylene glycols (PEGs) with the reporter dipeptide Met-betaAla for protein conjugation.

A new and more efficient route to the synthesis of branched PEG for protein conjugation, bearing a reporter dipeptide Met-betaAla, is described, which allows better purification of the final product by ion exchange chromatography. The product has the combined advantages of an 'umbrella-like' branched structure, which allows a better coverage of the protein surface, and the presence of the dipeptide Met-betaAla which has been used to detect the position of PEGylation within the peptide sequence.     

High-resolution X-ray diffraction study of the complex between endothiapepsin and an oligopeptide inhibitor: the analysis of the inhibitor binding and description of the rigid body shift in the enzyme.

The conformation of the synthetic renin inhibitor CP-69,799, bound to the active site of the fungal aspartic proteinase endothiapepsin (EC 3.4.23.6), has been determined by X-ray diffraction at 1.8 A resolution and refined to the crystallographic R factor of 16%. CP-69,799 is an oligopeptide transition--state analogue inhibitor that contains a new dipeptide isostere at the P1-P1' position. This dipeptide isostere is a nitrogen analogue of the well-explored hydroxyethylene dipeptide isostere, wherein the tetrahedral P1' C alpha atom has been replaced by trigonal nitrogen. The inhibitor binds in the extended conformation, filling S4 to S3' pockets, with hydroxyl group of the P1 residue positioned symmetrically between the two catalytic aspartates of the enzyme. Interactions between the inhibitor and the enzyme include 12 hydrogen bonds and extensive van der Waals contacts in all the pockets, except for S3'. The crystal structure reveals a bifurcated orientation of the P2 histidine side chain and an interesting relative rotation of the P3 phenyl ring to accommodate the cyclohexyl side chain at P1. The binding of the inhibitor to the enzyme, while producing no large distortions in the enzyme active site cleft, results in small but significant change in the relative orientation of the two endothiapepsin domains. This structural change may represent the action effected by the proteinase as it distorts its substrate towards the transition state for proteolytic cleavage.     

Access to the inaccessible sequence of cpn 60.1 (195-217) by temporary oxazolidine protection of selected amide bonds

The solid-phase peptide synthesis of a reportedly inaccessible peptide sequence of chaperonin 60.1 (195-219) is described using oxazolidine containing dipeptide building blocks ('pseudo-proline' dipeptide units). Two attempts at the synthesis of the chaperonin 60.1 sequence are outlined using one and two pseudo-proline units, respectively, and these results are compared with the outcome of an ordinary stepwise (double) coupling procedure. The only successful synthesis is that combining two pseudo-proline building blocks.     

Preparation of laurylsarcosyltaurine: a surface active constituent of crab gastric juice.

The conditions for the preparation of laurylsarcosyltaurine from lauric acid and sarcosyltaurine, a crystalline dipeptide, are described. The preparation of sarcosyltaurine from the reaction of taurine and the mixed anhydride of benzyloxycarbonylsarcosine and isobutyl chloroformate is also described.     

Synthesis of modular dipeptide mimetics on the basis of diazabicycloalkanes and derivatives thereof with sulphur containing side chains

Summary. We present the synthesis of new modular dipeptide mimetics based on diazabicycloalkane backbones. These diazabicycloalkanes are ligands for the prostate specific membrane antigen (PSMA), a well known tumor marker. Our previously described synthetic route to enantiomerically pure diazabicycloalkanes is extended to yield polyfunctional diazabicycloalkanes with a modular character using a new ring closing methodology. This, finally, allows us to attach linker moieties to different positions of the diazabicycloalkane scaffold providing conjugation sites to other functional molecules such as markers or cytostatic compounds. Furthermore, successful synthesis of sulphur-containing dipeptide analogues as for example CysX_AA- or HCysX_AA-mimetics on the basis of diazabicycloalkanes is described.     

Carnosine: biological role and prospects for use in medicine]

The biological role of the histidine-containing dipeptide carnosine (beta-alanyl-L-histidine) has been reviewed. The properties and putative biological role of the dipeptide in vertebrate tissues are considered. The antioxidative activity of carnosine and related compounds is described. The author's conception of the membranoprotective effect of carnosine on cells, tissues, and whole organism has been formulated. The properties of carnosine as an antistressory radioprotective agent are discussed. The data presented suggest that carnosine is a perspective immunomodulating tool which has many applications in medicine.     

氨基酸二肽甜味剂的开发研究进展

介绍了以氨基酸为原料生产的二肽甜味剂阿斯巴甜,阿力甜和乐甜的研究开发情况,并对这三种甜味剂的应用和市场情况作了概述。     

Structure of ethanol-inhibited porcine pepsin at 2-A resolution and binding of the methyl ester of phenylalanyl-diiodotyrosine to the enzyme

An account of x-ray crystallographic studies of monoclinic porcine pepsin crystals is presented. The chain fold specific for aspartyl proteases is described in detail. As the results of 2-A refinement have shown, the actual structure is that of ethanol-inhibited pepsin. The structure, although close to those of fungal aspartyl proteases, has some specific features: one of them is an insertion near the S'1 site which restricts the position of dipeptide substrates and makes their productive binding more probable than in the fungal enzymes. 3-A resolution data on the binding of the dipeptide phenylalanyl-diiodotyrosine methyl ester are discussed.     

Synthesis and SAR studies on azetidine-containing dipeptides as HCMV inhibitors

SAR studies on an azetidine-containing dipeptide prototype inhibitor of HCMV are described. Three series of structurally modified analogues, involving substitutions at the N- and C-terminus, and at the C-terminal side-chain were synthesized and evaluated for antiviral activity. Aliphatic or no substituents at the C-carboxamide group, an aliphatic C-terminal side-chain, as well as a benzyloxycarbonyl moiety at the N-terminus were absolute requirements for anti-HCMV activity. The conformational restriction induced by the 2-azetidine residue into the dipeptide derivatives, identified by (1)H NMR as a γ-type reverse turn, seems to have influence on the activity of these molecules.     

Escherichia coli K-12 Mutants Altered in the Transport Systems for Oligo- and Dipeptides

Two mutants of Escherichia coli K-12, defective in the oligopeptide and dipeptide transport system, are described. A mutant defective in the oligopeptide transport system (opp-1) was isolated as resistant to the inhibitory action of triornithine; this mutant is also resistant to glycylglycylvaline and does not concentrate (14)C-glycylglycylglycine, although it is still as sensitive as the parental strain to glycylvaline and valine. Starting from the opp-1 strain, a mutant defective also in the dipeptide transport system (dpp-1) was isolated; this mutant is resistant to the inhibitory action of glycylvaline, valylleucine, and leucylvaline and does not concentrate (14)C-glycylglycine, although it is still as sensitive as the parental strain to valine. The apparent kinetic constants for oligopeptide and dipeptide transport were measured. The opp marker is co-transducible with trp at 27 min on the E. coli genetic map. The dpp locus is separated from opp and is located between proC (10 min) and opp.     

A comparative study of warheads for design of cysteine protease inhibitors

The effects on potency of cruzain inhibition of replacing a nitrile group with alternative warheads were explored. The oxime was almost an order of magnitude more potent than the corresponding nitrile and has the potential to provide access to the prime side of the catalytic site. Dipeptide aldehydes and azadipeptide nitriles were found to be two orders of magnitude more potent cruzain inhibitors than the corresponding dipeptide nitriles although potency differences were modulated by substitution at P1 and P3. Replacement of the α methylene of a dipeptide aldehyde with cyclopropane led to a loss of potency of almost three orders of magnitude. The vinyl esters and amides that were characterized as reversible inhibitors were less potent than the corresponding nitrile by between one and two orders of magnitude.     

Focus on cyclo(His-Pro): history and perspectives as antioxidant peptide

Cyclo(His-Pro) is an endogenous cyclic dipeptide structurally related to tyreotropin-releasing hormone that was originally discovered in brain. In the central nervous system it has been described to exert multiple biological activities, which seem to be related to a presynaptic dopaminergic mechanism and include among the others a leptin-like function. It can be found in several body fluids and in the gastrointestinal tract where it has been suggested to act as a gut peptide with influence on the entero-insular axis. The oral administration of cyclo(His-Pro) and zinc was described to improve with a synergistic mechanism the glycaemic control in diabetes. The most intriguing function of this cyclic dipeptide is related with its neuroprotective role that was first reported in traumatic injuries of the spinal cord, and then confirmed in other models of experimental injuries of the nervous system. The mechanism that lies behind the neuroprotective activity of cyclo(His-Pro) remain poorly understood. Recent in vitro studies on rat pheochromocytoma PC12 cells have shown that it is a protective factor against stress stimuli and there is early pre-clinical evidence strongly suggesting that it enhances the expression of small heat shock proteins and antioxidant protection at the cellular level. Future research is underway to better characterize the possible use of this cyclic dipeptide in the therapy of neurodegenerative and metabolic disorders.     

Design and synthesis of dipeptidyl nitriles as potent, selective, and reversible inhibitors of cathepsin C

A series of dipeptide nitriles with a thienyl alanine in P2 were identified as potent and selective cathepsin C inhibitors. Incorporation of a substituted cyclopropyl moiety in P1 effectively protects these derivatives against hydrolase activity in whole blood.