1.Asymmetric synthesis of an N-acylpyrrolidine for inhibition of HCV polymerase.
Agbodjan AA1, Cooley BE, Copley RC, Corfield JA, Flanagan RC, Glover BN, Guidetti R, Haigh D, Howes PD, Jackson MM, Matsuoka RT, Medhurst KJ, Millar A, Sharp MJ, Slater MJ, Toczko JF, Xie S. J Org Chem. 2008 Apr 18;73(8):3094-102. doi: 10.1021/jo800062c. Epub 2008 Mar 22.
A practical asymmetric synthesis of a highly substituted N-acylpyrrolidine on multi-kilogram scale is described. The key step in the construction of the three stereocenters is a [3+2] cycloaddition of methyl acrylate and an imino ester prepared from l-leucine t-butyl ester hydrochloride and 2-thiazolecarboxaldehyde. The cycloaddition features novel asymmetric catalysis via a complex of silver acetate and a cinchona alkaloid, particularly hydroquinine, with complete diastereomeric control and up to 87% enantiomeric control. The alkaloid serves as a ligand as well as a base for the formation of the azomethine ylide or 1,3-dipole. Experiments have shown that the hydroxyl group of hydroquinine is a critical element for the enantioselectivities observed. The cycloaddition methodology is also applicable to methylvinyl ketone, providing access to either alpha- or beta-epimers of 4-acetylpyrrolidine depending on the reaction conditions utilized.
2.Peptide coupling between amino acids and the carboxylic acid of a functionalized chlorido-gold(I)-phosphane.
Kriechbaum M1, List M, Himmelsbach M, Redhammer GJ, Monkowius U. Inorg Chem. 2014 Oct 6;53(19):10602-10. doi: 10.1021/ic5017142. Epub 2014 Sep 9.
We have developed a protocol for the direct coupling between methyl ester protected amino acids and the chlorido-gold(I)-phosphane (p-HOOC(C6H4)PPh2)AuCl. By applying the EDC·HCl/NHS strategy (EDC·HCl = N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide hydrochloride, NHS = N-hydroxysuccinimide), the methyl esters of l-phenylalanine, glycine, l-leucine, l-alanine, and l-methionine are coupled with the carboxylic acid of the gold complex in moderate to good yields (62-88%). All amino acid tagged gold complexes were characterized by (1)H and (13)C NMR spectroscopy and high-resolution mass spectrometry. As corroborated by measurement of the angle of optical rotation, no racemization occurred during the reaction. The molecular structure of the leucine derivative was determined by single-crystal X-ray diffraction. In the course of developing an efficient coupling protocol, the acyl chlorides (p-Cl(O)C(C6H4)PPh2)AuX (X = Cl, Br) were also prepared and characterized.
3.Raloxifene prevents cardiac hypertrophy and dysfunction in pressure-overloaded mice.
Ogita H1, Node K, Liao Y, Ishikura F, Beppu S, Asanuma H, Sanada S, Takashima S, Minamino T, Hori M, Kitakaze M. Hypertension. 2004 Feb;43(2):237-42. Epub 2003 Dec 15.
17beta-estradiol reduces myocardial hypertrophy and left ventricular mass, suggesting that the selective estrogen receptor modulator raloxifene may have similar effects. However, it is not clear whether raloxifene inhibits both cardiac hypertrophy and dysfunction. We used transverse aortic-banded mice to produce pressure-overload cardiac hypertrophy and used neonatal rat ventricular cardiomyocytes to investigate the cellular mechanisms of raloxifene on cardiac hypertrophy. Left ventricular mass and fractional shortening of mice hearts were measured by transthoracic echocardiography. Protein synthesis of cardiomyocytes was evaluated by incorporation of [3H]leucine into cardiomyocytes exposed to angiotensin II. Phosphorylation of mitogen-activated protein (MAP) kinase was also observed in cardiomyocytes. Raloxifene prevented increases in left ventricular mass and decreases of fractional shortening at 4 weeks after aortic banding. Pretreatment with raloxifene before angiotensin II stimulation inhibited the increase in [3H]leucine incorporation into neonatal rat cardiomyocytes in a concentration-dependent manner.
4.Astrocytic gap junctional communication is reduced in amyloid-β-treated cultured astrocytes, but not in Alzheimer's disease transgenic mice.
Cruz NF1, Ball KK, Dienel GA. ASN Neuro. 2010 Aug 17;2(4):e00041. doi: 10.1042/AN20100017.
Alzheimer's disease is characterized by accumulation of amyloid deposits in brain, progressive cognitive deficits and reduced glucose utilization. Many consequences of the disease are attributed to neuronal dysfunction, but roles of astrocytes in its pathogenesis are not well understood. Astrocytes are extensively coupled via gap junctions, and abnormal trafficking of metabolites and signalling molecules within astrocytic syncytia could alter functional interactions among cells comprising the neurovascular unit. To evaluate the influence of amyloid-beta on astrocyte gap junctional communication, cultured astrocytes were treated with monomerized amyloid-β(1-40) (1 μmol/l) for intervals ranging from 2 h to 5 days, and the areas labelled by test compounds were determined by impaling a single astrocyte with a micropipette and diffusion of material into coupled cells. Amyloid-β-treated astrocytes had rapid, sustained 50-70% reductions in the area labelled by Lucifer Yellow, anionic Alexa Fluor® dyes and energy-related compounds, 6-NBDG (a fluorescent glucose analogue), NADH and NADPH.
