Synthesis of peptidyl ene diones: selective inactivators of the cysteine proteinases.

A series of synthetic peptides in which the C-terminal carboxyl grouping (-CO(2)H) of each has been chemically converted into a variety of ene dione derivatives (-CO-CH=CH-CO-X; X = -H, -Me, -OBut, -OEt, -OMe, -CO-OMe), have been prepared and tested as inactivators against typical members of the serine and cysteine protease families. For example, the sequences Cbz-Pro-Phe-CH=CH-CO-OEt (I) which fulfils the known primary and secondary specificity requirements of the serine protease chymotrypsin, and Cbz-Phe-Ala-CH=CH-CO-OEt (II) which represents a general recognition sequence for cysteine proteases such as cathepsins B, L and S, have been tested as putative irreversible inactivators of their respective target proteases. It was found that, whereas II, for example, functioned as a time-dependent, irreversible inactivator of each of the cysteine proteases, I behaved only as a modest competitive reversible inhibitor of chymotrypsin.

Tuning and enhancing enantioselective quenching of calixarene hosts by chiral guest amines.

The synthesis of a propranolol amide derivative of p-allylcalix[4]arene is described, which has been designed to behave as a molecular sensor capable of distinguishing chiral amines on the basis of their shape and chirality. This molecule can discriminate between the enantiomers of phenylalaninol through the quenching of the fluorescence emission in methanol in contrast to an (S)-dinaphthylprolinol calix[4]arene derivative, which can discriminate between the enantiomers of phenylglycinol, but not phenylalaninol. The separation between the naphthyl fluorophores and the hydrogen-bonding sites within the chiral cavity can be tuned to recognize guest amines with similar separation between aryl groups and hydrogen-bonding sites.

Cation Complexation by Chemically Modified Calixarenes. 11. Complexation and Extraction of Alkali Cations by Calix[5]- and -[6]arene Ketones. Crystal and Molecular Structures of Calix[5]arene Ketones and Na(+) and Rb(+) Complexes.

A series of four calix[5]arenes and three calix[6]arenes (R-calixarene-OCH(2)COR(1)) (R = H or Bu(t)) with alkyl ketone residues (R(1) = Me or Bu(t)) on the lower rim have been synthesized, and their affinity for complexation of alkali cations has been assessed through phase-transfer experiments and stability constant measurements. The conformations of these ketones have been probed by (1)H NMR and X-ray diffraction analysis, and by molecular mechanics calculations. Pentamer 3 (R = R(1) = Bu(t)) possesses a symmetrical cone conformation in solution and a very distorted cone conformation in the solid state.

Nonracemic 2-diazo-1-oxiranyl-ethanone, a versatile chiral epoxide educt in diazocarbonyl reactions.

(S)-(-)-2-Diazo-1-oxiranyl-ethanone, prepared in two steps from (R)-(+)-glycidol, has been employed as an intermediate in several characteristic diazocarbonyl reactions to yield novel, nonracemic products including an epoxy quinoxaline and epoxy thiazoles and oxazoles.

Potent new leucine aminopeptidase inhibitor of novel structure synthesised by a modified Wadsworth-Emmons (Horner) Wittig procedure.

The use of a leucine-derived alpha-keto-beta-aldehyde (glyoxal) as a substrate in the Horner-Emmons (Wadsworth) Wittig reaction has enabled the synthesis of (Z)-7-methyl-5(S)-amino-4-oxo-methyl-oct-2-eneoate. This novel compound is a potent inhibitor (Ki = 76 nM) of leucine aminopeptidase and provides an interesting new template for the development of metallopeptidase inhibitors.

Synthesis of ketomethylene amino pseudopeptide analogues via reductive amination of glyoxals derived from alpha-amino acids.

The reductive amination of an amino acid derived glyoxal, with the free amino group of a protected amino acid or oligopeptide fragment, has been developed as a simple and efficient method for the preparation of ketomethylene amino pseudo-oligopeptide isosteres Aa psi(COCH2NH)Aa. Trichlorosilane-DMF is the reagent of choice for the reduction.

Inhibitors of the chymotrypsin-like activity of proteasome based on di- and tri-peptidyl alpha-keto aldehydes (glyoxals).

A series of peptidyl alpha-keto aldehydes (glyoxals) have been synthesised as putative inhibitors of the chymotryptic-like activity of proteasome. The most potent peptides, Cbz-Leu-Leu-Tyr-COCHO and Bz-Leu-Leu-Leu-COCHO, function as slow-binding reversible inhibitors, exhibiting final Ki values of approximately 3.0 nM.

Solid phase synthesis of N-carboxy alkyl-containing peptides derived from enantiopure alpha-keto-beta-aminoacids.

alpha-Keto-beta-aminoacids 5a-c can be reductively aminated with the peptide sequence H2N-Leu-Val-Phe-Phe on a solid support to afford N-carboxy alkyl peptides 1a-c. The N-carboxy alkyl lysine derivative 7 was subsequently extended from the N-terminus with glutamine and histidine residues.

Molecular Baskets in Supercritical CO(2).

Calixarenes are synthetic macrocyclic compounds, described as "molecular baskets" as they possess high ionophoric selectivity and form inclusion complexes with many important ionic guests. In our initial work, hexameric and tetrameric tert-butylcalixarenes, unfunctionalized at the lower rim, are shown to be separable on a diol column using supercritical fluid chromatography with methanol/chloroform-modified CO(2) as mobile phase. The variation in capacity factors for these calixarenes was studied as a function of modifier composition.

Triterpenoids from Pulsatilla chinensis.

A new lupane type triterpenic acid, pulsatillic acid, and two new lupane type triterpenoid glycosides, pulsatilloside A and B, along with the known 23-hydroxybetulinic acid were isolated from the roots of Pulsatilla chinensis. Their structures were characterized as 3-oxo-23-hydroxy-lup-20(29)-en-28-oic acid, 3 beta, 23-dihydroxy-lup-20(29)-en-28-oic acid 3-O-alpha-L-arabinopyranoside and 3 beta, 23-dihydroxy-lup-20(29)-en-28-oic acid 28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside on the basis of hydrolysis and spectral evidence including two-dimensional relay HOHAHA, one-dimensional multiple relay COSY and ROESY NMR techniques. Pulsatillic acid exhibited cytotoxic activities against P-388, Lewis lung carcinoma and human large-cell lung carcinoma.

Patensin, a saponin from Pulsatilla patens var. multifida.

Patensin, a new triterpenoid glycoside, was isolated from the ethanolic extraction of the roots of Pulsatilla patens var. multifida. Its structure was established as hederagenin 3-O-beta-D-galactopyranosyl-(1-->2)-beta-D- glucopyranoside on the basis of hydrolysis and spectral evidence including 1D and 2D NMR techniques.

Symmetrical, unsymmetrical and bridged calix[4]arene derivatives as neutral carrier ionophores in poly (vinyl chloride) membrane sodium selective electrodes.

The complexing ability of a range of 19 symmetrical, unsymmetrical and bridged calix[4]arene derivatives having ester, ketone, amide, amine and thioether functionalities were determined by the picrate extraction method. On incorporating these calix[4]arene derivatives as neutral carrier ionophores in sodium-selective poly (vinyl chloride) membrane electrodes the performance was assessed on the basis of the sensitivity and selectivity over the alkali, alkaline earth metals and hydrogen and ammonium ions. The temperature dependence, response times and lifetimes were also determined.

Transition Metal Ion Complexation and Extraction by Hydroxamate Functionalised p-Tert-Butylcalix[4]Arenes.

The functionalisation of macrocyclic p-tertbutylcalix[4]arenes at the lower rim with hydroxamic acid and proline hydroxamic acid groups gives the calixarenes chelating properties similar to siderophores. The (1)H NMR spectrum of p-tertbutylcalix[4]arene tetrahydroxamic acid shows a broad band at 10.8 ppm in DMSO-d(6) attributed to NHOH protons.

Peptide glyoxals: a novel class of inhibitor for serine and cysteine proteinases.

A series of novel synthetic dipeptides, containing a C-terminal glyoxal grouping (-COCHO), have been tested as inhibitors against typical members of the serine- and cysteine-proteinase families. For example, the sequences benzyloxycarbonyl (Cbz)-Pro-Phe-CHO (I) and Cbz-Phe-Ala-CHO (II), which fulfil the known primary and secondary specificity requirements of chymotrypsin and cathepsin B respectively, have been found to be potent reversible inhibitors of their respective target proteinase. Thus I was found to inhibit chymotrypsin with a Ki of approximately 0.

Calixarene-based potentiometric ion-selective electrodes for silver.

Four lipophilic sulphur and/or nitrogen containing calixarene derivatives have been tested as ionophores in Ag(I)-selective poly (vinyl chloride) membrane electrodes. All gave acceptable linear responses with one giving a response of 50 mV/dec in the Ag(I) ion activity range 10(-4)-10(-1)M and high selectivity towards other transition metals and sodium and potassium ions. This ionophore was also tested as a membrane coated glassy-carbon electrode where the sensitivity and selectivity of the conventional membrane electrode was found to be repeated.