Synthesis and structure-activity relationships of peptidyl alpha-keto heterocycles as novel inhibitors of prolyl endopeptidase.

The preparation and in vitro prolyl endopeptidase (PEP) inhibitory activity of a series of alpha-keto heterocyclic compounds is described. The design is based on the introduction of alpha-keto heterocycles at the C-terminal end of substrate-like peptides. Many of the compounds including those substituted with thiazole, benzothiazole, benzoxazole, imidazole, and pyridine groups exhibit IC50 potencies of PEP inhibition at nanomolar levels. Structure-activity studies of the C-terminal heterocyclic groups indicate the importance of an sp2 nitrogen atom at a beta-position from the adjoining ketone carbonyl group. This heterocyclic nitrogen atom would provide a critical hydrogen-bond interaction with the histidine residue of the catalytic triad in PEP. Our inhibitors would extend the generality of the alpha-keto heterocycle design to another serine protease.

Fungal metabolites, PF1092 compounds and their derivatives, are nonsteroidal and selective progesterone receptor modulators.

The potential of new nonsteroidal progesterone receptor ligands, the derivatives of PF1092C ((4aR,5R,6R,7S)-6,7-dihydroxy-4a,5,6,7-tetrahydro-3,4a,5-trimethylnaphtho[2,3-b]furan-2(4H)-one) discovered from fungal metabolites, was evaluated. PF1092A ((4aR,5R,6R,7S)-6-acetoxy-7-hydroxy-4a,5,6,7-tetrahydro-3,4a,5-trimethylnaphtho[2,3-b]furan-2(4H)-one) showed good and moderate affinity for porcine and human progesterone receptors in in vitro receptor binding assays, respectively, and partial agonist activity for the progesterone receptor, as determined in assays of two types of progesterone-dependent enzymes in human mammary carcinoma T47D cells. The derivative of PF1092C, CP8481, ((4aR,5R,6R,7S)-6-(2-furancarbonyloxy)-7-hydroxy-4a,5,6,7-tetrahydro-3,4a,5-trimethylnaphtho[2,3-b]furan-2(4H)-one) possessed better affinity for both progesterone receptors and showed less cross-reactivity for other steroid receptors, such as rat androgen receptor, human glucocorticoid receptor, and human estrogen receptor, and was a more potent modulator of the progesterone receptor than PF1092A. CP8400 ((4aR,5R,6R,7S)-6,7-diacetoxy-4a,5,6,7-tetrahydro-3,4a,5-trimethylnaphtho[2,3-b]furan-2(4H)-one) and CP8401 ((4aR,5R,6R,7S)-6,7-dipropionyloxy-4a,5,6,7-tetrahydro-3,4a,5-trimethylnaphtho[2,3-b]furan-2(4H)-one), other derivatives, were indicated to be progesterone receptor antagonists. These results suggest that PF1092 compounds can serve as a new pharmacophore for potent and specific nonsteroidal progesterone receptor modulators.

Synthesis and antibacterial activity of novel 2-methyl-1-oxacephalosporins.

New 2-methyl-1-oxacephem compounds having 2-(2-aminothiazol-4-yl)-2-(alkoxyimino)acetamido substituents at C-7 and various C-3 side chains were synthesized starting from (3R,4S)-phenyloxazolinoazetidinone (8). Introduction of the 2 beta-methyl group into the 1-oxacephem nucleus increased the stability to beta-lactamases. OCP-9-176 (7b) having the (1-methylpyridinium-4-yl)thiomethyl group at C-3 showed potent antibacterial activity and a broad spectrum.

A new aminothiazolylcephalosporin having 1-carboxyethoxyimino group, ME1228.

Aminothiazolylacetamidocephalosporins having 1-carboxyethoxyimino groups were synthesized and found to have excellent antibacterial activities including anti-pseudomonal activity and low toxicities. Among these cephalosporins, ME1228 having (S)-1-carboxyethoxyimino substituent and being combined with an (N-ethyl-4-pyridinio)thiomethyl group at C-3 showed marked therapeutic effects against systemic infections in mice and was selected as the best candidate for further evaluation.

Cladinose analogues of sixteen-membered macrolide antibiotics. IV. Improved therapeutic effects of 4-O-acyl-L-cladinose analogues of sixteen-membered macrolide antibiotics.

Six derivatives of sixteen-membered macrolides possessing 4-O-acyl-alpha-L-cladinose as a neutral sugar were synthesized via 3"-methylthiomethyl ether intermediates in reasonable yield. Introduction of a methyl group on the 3"-hydroxyl group of midecamycin A1 was effective for enhancing its antibacterial activity. All these derivatives exhibited excellent therapeutic effects in mice, and some of them showed improved pharmacokinetics compared with the natural antibiotics (mycarose type) in mice. Facile synthesis of 9-O-acylated analogues are also described.

Contrast inversion in the epifluorescence of cholesterol-phospholipid monolayers.

A number of dihydrocholesterol-phospholipid mixtures have been examined using the epifluorescence microscopy of monolayers at the air-water interface. These mixtures form two coexisting liquids. Fluorescence contrast was provided using a variety of different lipid probes. With increasing monolayer pressure, all of the charged probes show contrast inversion at higher dihydrocholesterol concentrations. That is, with increasing pressure the charged probes transfer from one liquid to the other, reversing the fluorescence contrast. A wide variety of phospholipids were studied, and the inversion was seen in all cases. In the inverted state and at the higher dihydrocholesterol concentrations, the immiscibility persists to the highest pressures employed, 30-40 mN/m. The data show that binary dihydrocholesterol-phospholipid mixtures can form three distinct liquids, one of which is interpreted as a phase rich in condensed complex.

Synthesis and structure-activity relationships of new non-steroidal progesterone receptor ligands.

In order to study structure-activity relationships, a series of new non-steroidal progesterone receptor ligands based on PF1092A was synthesized with structural modifications (mostly introduction or removal of a methyl group) at the 3-, 4-, 5-, 7- or 9-position in the 6-acetoxy-4a, 5, 6, 7-tetrahydro-3, 4a, 5-trimethylnaphtho[2,3-b]furan-2(4H)-one skeleton. Critical positions for high binding affinity to the progesterone receptor were identified.

Sequence-dependent dynamics of duplex DNA: the applicability of a dinucleotide model.

The short-time (submicrosecond) bending dynamics of duplex DNA were measured to determine the effect of sequence on dynamics. All measurements were obtained from a single site on duplex DNA, using a single, site-specific modified base containing a rigidly tethered, electron paramagnetic resonance active spin probe. The observed dynamics are interpreted in terms of single-step sequence-dependent bending force constants, determined from the mean squared amplitude of bending relative to the end-to-end vector using the modified weakly bending rod model. The bending dynamics at a single site are a function of the sequence of the nucleotides constituting the duplex DNA. We developed and examined several dinucleotide-based models for flexibility. The models indicate that the dominant feature of the dynamics is best explained in terms of purine- and pyrimidine-type steps, although distinction is made among all 10 unique steps: It was found that purine-purine steps (which are the same as pyrimidine-pyrimidine steps) were near average in flexibility, but the pyrimidine-purine steps (5' to 3') were nearly twice as flexible, whereas purine-pyrimidine steps were more than half as flexible as average DNA. Therefore, the range of stepwise flexibility is approximately fourfold and is characterized by both the type of base pair step (pyrimidine/purine combination) and the identity of the bases within the pair (G, A, T, or C). All of the four models considered here underscore the complexity of the dependence of dynamics on DNA sequence with certain sequences not satisfactorily explainable in terms of any dinucleotide model. These findings provide a quantitative basis for interpreting the dynamics and kinetics of DNA-sequence-dependent biological processes, including protein recognition and chromatin packaging.

Sequence-dependent dynamics in duplex DNA.

The submicrosecond bending dynamics of duplex DNA were measured at a single site, using a site-specific electron paramagnetic resonance active spin probe. The observed dynamics are interpreted in terms of the mean squared amplitude of bending relative to the end-to-end vector defined by the weakly bending rod model. The bending dynamics monitored at the single site varied when the length and position of a repeated AT sequence, distant from the spin probe, were changed. As the distance between the probe and the AT sequence was increased, the mean squared amplitude of bending seen by the probe due to that sequence decreased. A model for the sequence-dependent internal flexural motion of duplex DNA, which casts the mean squared bending amplitudes in terms of sequence-dependent bending parameters, has been developed. The best fit of the data to the model occurs when the (AT)(n) basepairs are assumed to be 20% more flexible than the average of the basepairs within the control sequence. These findings provide a quantitative basis for interpreting the kinetics of biological processes that depend on duplex DNA flexibility, such as protein recognition and chromatin packaging.