Amide Formation: Choosing the Safer Carbodiimide in Combination with OxymaPure to Avoid HCN Release.

It has been reported that DIC can react with OxymaPure to render an oxadiazole compound with the concomitant formation of HCN. Here we demonstrate that this reaction is not a feature of all carbodiimides but rather depends on the alkyl structure that flanks the two N atoms of the carbodiimide. Furthermore, we have identified two carbodiimides, TBEC and EDC·HCl, whose reaction with OxymaPure is exempt from HCN formation.

In vitro binding and functional studies of Ac-RYYRIK-ol and its derivatives, novel partial agonists of the nociceptin/orphanin F/Q receptor.

Following the discovery of nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) and its endogenous ligand, an extensive search has started to find selective agonists and antagonists targeting this novel receptor-ligand system due to their therapeutic potentials. By the help of the combinatorial chemistry a series of hexapeptides with a general formula of Ac-RYY-R/K-W/I-R/K-NH(2) having high NOP receptor affinity and selectivity were identified. On the basis of this information we developed a number of novel compounds.

The effect of peptide length on the cleavage kinetics of 2-chlorotrityl resin-bound ethers.

Different characteristics of cleavage kinetics of resin-bound amino alcohols and their peptide derivatives were observed in acid containing protic and aprotic solvent mixtures. The hydrolysis reactions are hindered by steric crowding around the cleaving C--O bond and accelerated by the special solvation effect of CF(3)CH(2)OH on the peptide chain as well as the increase of the strength and concentration of the acid. In trifluoroacetic acid containing mixtures, trifluoroacetylation of the peptide alcohols was detected.

Endomorphin synthesis in rat brain from intracerebroventricularly injected [3H]-Tyr-Pro: a possible biosynthetic route for endomorphins.

In spite of concentrated efforts, the biosynthetic route of mu-opioid receptor agonist brain tetrapeptide endomorphins (Tyr-Pro-Trp-Phe-NH2 and Tyr-Pro-Phe-Phe-NH2), discovered in 1997, is still obscure. We report presently that 30 min after intracerebroventricular injection of 20 or 200 microCi [3H]Tyr-Pro (49.9 Ci mmol(-1)) the incorporated radioactivity was found in endomorphin-related tetra- and tripeptides in rat brain extracts.

Partial and full agonism in endomorphin derivatives: comparison by null and operational model.

The partial mu-opioid receptor pool inactivation strategy in isolated mouse vas deferens was used to determine partial agonism of endomorphins and their analogs (endomorphin-1-ol, 2',6'-dimethyltyrosine (Dmt)-endomorphin-1, endomorphin-2-ol and (D-Met2)-endomorphin-2) using morphine, normorphine, morphiceptin, (D-Ala2,MePhe4,Gly5-ol)-enkephalin (DAMGO) and its amide (DAMGA) as reference opioid agonists. Agonist affinities (KA) and efficacies were assessed both by the "null" and the "operational" method. The KA values determined by the two methods correlated significantly with each other and also with the displacing potencies against 3H-naloxone in the receptor binding assay in the presence of Na+.

High-performance liquid chromatographic enantioseparation of bicalutamide and its related compounds.

Direct high-performance liquid chromatographic methods were developed for the enantioseparation of (R,S)-bicalutamide (1) and its analogs (+/-)-3-chloro-N-(4-cyano-3-(trifluoromethyl)phenyl)-2-hydroxy-2-methylpropanamide (2), (+/-)-N-(4-cyano-3-(trifluoro-methyl)phenyl)-2-methyloxirane-2-carboxamide (3), (+/-)-4-fluorophenylsulfonyl-2-hydroxy-2-methylpropionic acid (4) and (+/-)-3-hydroxy-N-(4-cyano-3-(trifluoromethyl)phenyl)-2-hydroxy-2-methylpropanamide (5). The methods involved the use of a cellulose-based Chiralcel OD-H, macrocyclic glycopeptide-based Chirobiotic T, TAG and R, beta-cyclodextrin-based Cyclobond I 2000SN and t-butyl carbamate-derivatized quinine-based columns. The conditions affording the best resolution were found by selection and variation of the mobile-phase compositions, and the differences in separation capability of the methods were noted.

Nociceptin antagonism: probing the receptor by N-acetyl oligopeptides.

In search for effective antagonist structures for the nociceptin (NOP) receptor, a number of N-acylated oligopeptides, including N-acyl tetra- and pentapeptides selective for the kappa-opioid receptor, as well as N-acyl hexapeptides bearing the Ac-Arg-Tyr-Tyr-Arg-Ile-Lys (Ac-RYYRIK) core sequence originally isolated from combinatorial chemical libraries, were synthesized and studied in radioreceptor binding assays, [(35)S]GTPgammaS functional tests and in mouse vas deferens (MVD) bioassays. The properties of the novel antagonist candidates were compared to known antagonists. A new antagonist structure with a reduced, primer alcohol C-terminus, Ac-Arg-Tyr-Tyr-Arg-Ile-lysinol (Ac-RYYRIK-ol) was described in the mouse vas deferens tests, showing an equilibrium inhibitory constant value (K(e)) of 2.

Structure-oriented rational design of chymotrypsin inhibitor models.

Three peptides modelling a highly potent, 35-residue chymotrypsin inhibitor (Schistocerca gregaria chymotrypsin inhibitor) were designed and synthesized by convergent peptide synthesis. For each model peptide, the inhibitory constant (Ki) on chymotrypsin and the solution structure were determined. In addition, molecular dynamics calculations were performed for all of them.

Engineering new peptidic inhibitors from a natural chymotrypsin inhibitor.

Three model peptides of different sizes (17-24 amino acid residues) mimicking the chymotrypsin inhibitor SCGI (a peptide of 35 amino acid residues) isolated from Schistocerca gregaria were designed and prepared by convergent peptide synthesis. Selective formation of disulphide bridges in the closing step was achieved without selective protection of cysteine residues. The natural pattern of the two disulphide bridges was determined by 2D homonuclear 1H NMR techniques.

Substrate-dependent competency of the catalytic triad of prolyl oligopeptidase.

Prolyl oligopeptidase, a serine peptidase unrelated to trypsin and subtilisin, is implicated in memory disorders and is an important target of drug design. The catalytic competence of the Asp(641) residue of the catalytic triad (Ser(554), Asp(641), His(680)) was studied using the D641N and D641A variants of the enzyme. Both variants displayed 3 orders of magnitude reduction in k(cat)/K(m) for benzyloxycarbonyl-Gly-Pro-2-naphthylamide.

Calpastatin subdomains A and C are activators of calpain.

The inhibitory domains of calpastatin contain three highly conserved regions, A, B, and C, of which A and C bind calpain in a strictly Ca(2+)-dependent manner but have no inhibitory activity whereas region B inhibits calpain on its own. We synthesized the 19-mer oligopeptides corresponding to regions A and C of human calpastatin domain I and tested their effect on human erythrocyte mu-calpain and rat m-calpain. The two peptides significantly activate both calpains: the Ca(2+) concentration required for half-maximal activity is lowered from 4.