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Relevant academic research and scientific papers

A general method for the facile synthesis of optically active 2-substituted piperazines via functionalized 2,5-diketopiperazines

Upon utilization of some common methods described in the literature for the synthesis of chiral, 2-substituted 2,5-diketopiperazines, extensive racemization was observed. Further investigation showed that heating in the presence of a mild base racemized the chiral center in the product diketopiperazines. A generalized, readily scalable route was sought and, after investigating the effect of base and temperature, conditions were identified that promoted cyclization without erosion of enantiomeric excess. An array of functionalization was tolerated and this procedure serves as a useful and reliable method for the facile synthesis of this important class of compounds.

Concurrent display of both α- and β-turns in a model peptide

This article describes a model peptide that concurrently displays both α- and β-turns, as demonstrated by structural investigations using single crystal X-ray crystallography and solution-state NMR studies. The motif reported herein has the potential for

Bioinspired modular synthesis of elastin-mimic polymers to probe the mechanism of elastin elasticity

Bioinspired modular synthesis of elastin-mimic polymers (EMPs) is achieved via Cu-catalyzed alkyne-azide cyclization (CuAAC). By changing the module, EMPs with different secondary structures determined by circular dichroism (CD) spectra in trifluoroethanol (TFE) solution are obtained. The EMPs are characterized by measuring the lower critical solution temperatures (LSCTs) and the bulk mechanic properties under the conditions of both dry and hydrated forms. The unique molecular design enables us to probe mechanistic questions and assess the structure-property relationship of the EMPs. Our results indicate that, instead of a highly organized secondary structure, hydrophobic hydration is critical for the elasticity of EMPs.

Ring-closing alkyne metathesis approach toward the synthesis of alkyne mimics of thioether A-, B-, C-, and DE-ring systems of the lantibiotic nisin Z

(Chemical Equation Presented) Ring-closing alkyne metathesis toward the synthesis of the alkyne-brigded A-, B-, C-, and (D)E-ring mimics of the peptide antibiotic nisin Z is described. We have successfully synthesized alkyne-bridged cyclic peptides containing 4-7 amino acid residues in yields ranging from 18 to 82%.

SUBSTITUTED HEXAHYDROPYRROLO[1,2-A]PYRAZINES, OCTAHYDROPYRIDO[1,2-A]-PYRAZINES AND DECAHYDROPYRAZINO[1,2-A]AZEPINES

Novel substituted hexahydropyrrolo[1,2-a]pyrazines, octahydropyrido[1 , 2-a]-pyrazines and decahydropyrazino[1,2-a]azepines, use of these compounds as pharmaceutical compositions, pharmaceutical compositions comprising the compounds, and a method of treatment employing these compounds and compositions. The compounds show a high and selective binding affinity to the histamine H3 receptor indicating histamine H3 receptor antagonistic, inverse agonistic or agonistic activity. As a result, the compounds are useful for the treatment of diseases and disorders related to the histamine H3 receptor.

SUBSTITUTED HEXAHYDROPYRROLO[1,2-A]PYRAZINES, OCTAHYDROPYRIDO[1,2-A]PYRAZINES AND DECAHYDROPYRAZINO[1,2-A]AZEPINES

Novel substituted hexahydropyrrolo[1,2-a]pyrazines, octahydropyrido[1,2-a]-pyrazines and decahydropyrazino[1,2-a]azepines, use of these compounds as pharmaceutical compositions, pharmaceutical compositions comprising the compounds, and a method of treatment employing these compounds and compositions. The compounds show a high and selective binding affinity to the histamine H3 receptor indicating histamine H3 receptor antagonistic, inverse agonistic activity. As a result, the compounds are useful for the treatment of diseases and disorders related to the histamine H3 receptor.

Synthesis and Evaluation of Conformationally Restricted N--N-methyl-2-(1-pyrrolidinyl)ethylamines at ? Receptors. 2. Piperazines, Bicyclic Amines, Bridged Bicyclic Amines, and Miscellaneous Compounds

As a continuation of our earlier study (J.Med.Chem. 1992, 35, 4334-4343) we conformationally restricted the ?-receptor ligand 2-(1-pyrrolidinyl)-N--N-methylethylamine (1) by incorporating it into a series of homologous piperazines 3-9 and homopiperazines 10 and 11, diazabicyclononanes and decanes, bridgehead bicyclooctanes and nonanes as well as other miscellaneous compounds. ?-Receptor binding affinites were obtained using (+)-pentazocine in guinea pig brain membrane ?1 sites.The studies suggest that the nitrogen lone pair orient ation found in the piperazines affords the strongest binding interaction.Other nitrogen lone pair orientations or compounds representing unlikely staggered conformations of 1 -1,4-diazabicyclononane (16)> show very weak ? interaction.Comperison of the binding data of different N-substituted homologues of 1 with those of the 1--4-alkylpiperazines suggests that the two nitrogen atoms of 1 are working in opposition to one another in terms of their sensitivity to steric bulk.The high binding affinity of the 1,4-diazabicyclononanes 12 suggests that these may approximate the methyl and pyrrolidine ring conformations found in 1 when it is bound to the ? receptor.Compound 12 exhibited a 4-fold enantioselectivity favoring (+)-12.The synthesis of 6,7-dichloro-2-amino>tetralin (19) and its desmethyl derivative 20 permitted constraint of the 3,4-dichlorophenyl and N-methyl moieties of 1 into a gauche orientation.The binding data suggests that this conformation in 1 favors strong binding interaction at ?-receptors. ?-Receptor K1's ra nged from 0.55 nM for 1--4-n-butylpiperazine (7) to 654 nM for 16.Overall comparison of the results indicate that 1 is subject to considerable conformational freedom and suggests that the ?-receptor is not subject to rigid stereochemical restraints with 1.These results add to our earlier study where we restrained 1 using simple monocyclic heterocycles.