Pyrrolidine/Azepane Ring Expansion via Intramolecular Ullmann-Type Annulation/Rearrangement Cascade: Synthesis of Highly Functionalized 1H-Benzazepines.

5-Arylpyrrolidine-2-carboxylates with an ortho-halogen substituent at 5-aryl and an electron-withdrawing group at the C4 position of the pyrrolidine ring were transformed into 1H-benzo[b]azepine-2-carboxylates under Cu(I) promotion and microwave activation. Reaction promoter copper(I) thiophene-2-carboxylate has been generated in situ in the reaction's environment from Cu2O and thiophene-2-carboxylic acid. Functionalized 1H-benzo[b]azepine-2-carboxylates were obtained in racemic and optically active forms in 67-89% yields. Subsequent stereoselective 1,3-dipolar cycloaddition and an Ullmann-type annulation/rearrangement cascade (UARC) ensure a synthetic route to oligomeric optically active benzazepine species with a well-defined 3D-structure.

Interplay of Pyrrolidine Units with Homo/Hetero Chirality and CF3-Aryl Substituents on Secondary Structures of ß-Proline Tripeptides in Solution.

All possible variants of ß-proline functionalized tripeptides consisting of homo/hetero chiral monomeric all-cis 5-arylpyrrolidine-2,4-dicarboxylate units were synthesized for the first time by a nonpeptidic coupling method based on 1,3-dipolar cycloaddition chemistry of azomethine ylides. Secondary structures of ß-proline tripeptides in solution were determined using the NMR spectroscopy data. o-(Trifluoromethyl)phenyl substituent contributes to stereoselectivity of 1,3-dipolar cycloaddition and structural features of ß-proline tripeptides. A ß-proline CF3-tripeptide with alternating absolute chirality between adjacent pyrrolidine units mimics natural PPII helix secondary structure.

Chemoselectivity issues of the asymmetric interaction between cyclohexanone, ß-nitrostyrene, and benzoic acid under 5-aryl prolinate's organocatalysis.

4-l-menthyloxycarbonyl 5-aryl prolinates were studied as organocatalysts of a novel three-component reaction of cyclohexanone, benzoic acid, and ß-nitrostyrene. The presence of ortho-halogen atom in 5-aryl fragment of the catalyst is favored for driving the formation of chiral 7a-hydroxyoctahydro-2H-indol-2-one scaffold. 5-(o-Chlorophenyl) prolinate selectively afforded 3-phenyl-7a-hydroxyoctahydro-2H-indol-2-one with ee 63%, whereas 5-phenyl prolinate led to conjugation of ß-nitrostyrene to cyclohexanone (the Michael adduct). Plausible chlorine effect is accounted for the specific interaction of the 5-aryl prolinate enamine intermediate with ß-nitrostyrene in the transition state.

Crystal structure of 4-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yl] 2-methyl (2S,4S,5R)-1-[(2S,3R,5R)-5-meth-oxy-carbonyl-2-(2-methyl-phen-yl)pyrrolidine-3-carbon-yl]-5-(2-methyl-phen-yl)pyrrolidine-2,4-di-carboxyl-ate.

The title compound, C38H50N2O7, represents a chiral ß-proline dipeptide. Corresponding stereogenic centres of constituting pyrrolidine units have opposite absolute configurations. The central amide fragment is planar within 0.1 Šand adopts a Z configuration along the N-CO bond. In the crystal, the hydrogen atoms of the methyl-ene groups form several short inter-molecular C-H⋯O contacts with the carbonyl oxygen atoms of an adjacent mol-ecule. The only active amino hydrogen atom is not involved in hydrogen bonding.

Theoretical and NMR Conformational Studies of ß-Proline Oligopeptides With Alternating Chirality of Pyrrolidine Units.

Synthetic ß-peptides are potential functional mimetics of native α-proteins. A recently developed, novel, synthetic approach provides an effective route to the broad group of ß-proline oligomers with alternating patterns of stereogenic centers. Conformation of the pyrrolidine ring, Z/E isomerism of ß-peptide bonds, and hindered rotation of the neighboring monomers determine the spatial structure of this group of ß-proline oligopeptides. Preferences in their structural organization and corresponding thermodynamic properties are determined by NMR spectroscopy, restrained molecular dynamics and quantum mechanics. The studied ß-proline oligopeptides exist in dimethyl sulfoxide solution in a limited number of conformers, with compatible energy of formation and different spatial organization. In the ß-proline tetrapeptide with alternating chirality of composing pyrrolidine units, one of three peptide bonds may exist in an E configuration. For the alternating ß-proline pentapeptide, the presence of an E configuration for at least of one ß-peptide bond is mandatory. In this case, three peptide bonds synchronously change their configurations. Larger polypeptides may only exist in the presence of several E configurations of ß-peptide bonds forming a wave-like extended structure.

Enantiomerically pure ß-dipeptide derivative induces anticancer activity against human hormone-refractory prostate cancer through both PI3K/Akt-dependent and -independent pathways.

The use of peptides that target cancer cells and induce anticancer activities through various mechanisms is developing as a potential anticancer strategy. KUD983, an enantiomerically pure ß-dipeptide derivative, displays potent activity against hormone-refractory prostate cancer (HRPC) PC-3 and DU145 cells with submicromolar IC50. KUD983 induced G1 arrest of the cell cycle and subsequent apoptosis associated with down-regulation of several related proteins including cyclin D1, cyclin E and Cdk4, and the de-phosphorylation of RB. The levels of nuclear and total c-Myc protein, which could increase the expression of both cyclin D1 and cyclin E, were profoundly inhibited by KUD983. Furthermore, it inhibited PI3K/Akt and mTOR/p70S6K/4E-BP1 pathways, the key signaling in multiple cellular functions. The transient transfection of constitutively active myristylated Akt (myr-Akt) cDNA significantly rescued KUD983-induced caspase activation but did not blunt the inhibition of mTOR/p70S6K/4E-BP1 signaling cascade suggesting the presence of both Akt-dependent and -independent pathways. Moreover, KUD983-induced effect was enhanced with the down-regulation of anti-apoptotic Bcl-2 members (e.g., Bcl-2, and Mcl-1) and IAP family members (e.g., survivin). Notably, KUD983 induced autophagic cell death using confocal microscopic examination, tracking the level of conversion of LC3-I to LC3-II and flow cytometric detection of acidic vesicular organelles-positive cells. In conclusion, the data suggest that KUD983 is an anticancer ß-dipeptide against HRPCs through the inhibition of cell proliferation and induction of apoptotic and autophagic cell death. The suppression of signaling pathways regulated by c-Myc, PI3K/Akt and mTOR/p70S6K/4E-BP1 and the collaboration with down-regulation of Mcl-1 and survivin may explain KUD983-induced anti-HRPC mechanism.

Control of Azomethine Cycloaddition Stereochemistry by CF3 Group: Structural Diversity of Fluorinated ß-Proline Dimers.

ß-Proline-functionalized dimers consisting of homochiral monomeric units were synthesized by a non-peptidic coupling method for the first time. The applied synthetic methodology is based on 1,3-dipolar cycloaddition chemistry of azomethine ylides and provides absolute control over the ß-proline backbone stereogenic centers. An o-(trifluoromethyl)phenyl substituent contributes to appropriate stabilization of the definite acrylamide chiral cis conformation and to achieve the dipole reactivity that is not observed for aryl groups lacking strong electronegative character.

Menthols as Chiral Auxiliaries for Asymmetric Cycloadditive Oligomerization: Syntheses and Studies of ß-Proline Hexamers.

To produce a novel class of structurally ordered poly-ß-prolines, an emergent method for synthesizing chiral ß-peptide molecular frameworks was developed based on 1,3-dipolar cycloaddition chemistry of azomethine ylides. Functionalized short ß-peptides with up to six monomeric residues were efficiently synthesized in homochiral forms using a cycloadditive oligomerization approach. X-ray, NMR, and CD structural analyses of the novel ß-peptides revealed secondary structure features that were generated primarily by Z/E-ß-peptide bond isomerism. Anticancer in cellulo activity of the new ß-peptides toward hormone-refractory prostate cancer cells was observed and was dependent on the absolute configuration of the stereogenic centers and the chain length of the ß-proline oligomers.

Structural studies and anticancer activity of a novel class of ß-peptides.

Functionalized oligomeric organic compounds with well-defined ß-proline scaffold have been synthesized by a cycloadditive oligomerization approach in racemic and enantiopure forms. The structure of the novel ß-peptides was investigated by NMR spectroscopic and X-ray methods determining the conformational shapes of the ß-proline oligomers in solution and solid states. The main structural elements subject to conformational switches are ß-peptide bonds between 5-arylpyrrolidine-2-carboxylic acid units existing in Z/E configurations. The whole library of short ß-peptides and intermediate acrylamides has been tested on antiproliferative activity towards the hormone-refractory prostate cancer cell line PC-3 revealing several oligomeric compounds with low micromolar and submicromolar activities. Bromine-substituted dimeric and trimeric acrylamides induced caspase-dependent apoptosis of PC-3 cells through cell-cycle arrest and mitochondrial damage.

(1SR,3RS,3aSR,6aRS)-Methyl 5-methyl-4,6-dioxo-3-[2-(trifluoro-meth-yl)phen-yl]octa-hydro-pyrrolo-[3,4-c]pyrrole-1-carboxyl-ate.

In the title compound, C(16)H(15)F(3)N(2)O(4), the relative stereochemistry of the four stereogenic C atoms has been determined. The carb-oxy-methyl and 2-(trifluoro-meth-yl)-phenyl substituents of the pyrrolidine cycle have a cis mutual arrangement. The five-membered saturated aza-cycle adopts an envelope conformation with the N atom occupying the flap position. In the crystal, adjacent mol-ecules are combined in centrosymmetric dimers by two weak N-H⋯O hydrogen bonds.