C-methylation of sucrose: synthesis of 6- and 6′-C-methylsucrose

2,3,4,6,1′,3′,4′-Hepta-O-benzylsucrose, obtained by acid-catalysed hydrolysis of the 6′-O-trityl derivative, was oxidised with the Pfitzner-Moffatt reagent and the product was alkylated with methylmagnesium iodide. Removal of the protecting groups then gave a mixture of diastereomers, namely 7-deoxy-β-d-altro and -α-l-galacto-hept-2-ulofuranosyl α-d-glucopyranoside. Application of this reaction sequence to 2,3,4,1′,3′,4′,6′-hepta-O-benzylsucrose afforded β-d-fructo-furanosyl 7-deoxy-dl-glycero-α-d-gluco-heptopyranoside.     

6′-substituted and 6′,6″-disubstituted derivatives of raffinose

The reaction of 6′-chloro-6′-deoxyraffinose deca-acetate with a variety of nucleophilic anions (Br^-,I^-,N^-₃) gave the corresponding 6′-substituted raffinoses. The 6′-azide was further converted into 6′-amino-6′-deoxyraffinose, isolated as its N-acetyl derivative, and silver fluoride-induced elimination of hydrogen iodide from the 6′-iodide gave the 6′-deoxy-5′-ene. Treatment of 6′-chloro-6′-deoxyraffinose and 6′,6″-dichloro-6′,6″-dideoxyraffinose with base afforded, respectively, 3′,6′-anhydro-and 3′,6′;3″,6″-dianhydro-raffinose in high yields. In addition, the dichloride was converted into 6′,6″-diazido-6′,6″-dideoxyraffinose.     

Electrochemical studies of η5-cyclopentadienyliron hexafluorophosphates of η6-substituted arenes and η6-heterocycles

Polarographic half-wave potentials for two reduction steps of 49 cyclopentadienyliron complexes of substituted arenes or heterocycles in dimethylformamide were determined. A fast cyclic voltammetry (10–40 V/s) was used to study the electron transfer kinetics of some of these complexes. After correction for the double layer effects, the rate constants of all the complexes studied show that the transfer of electrons in the second reduction step occurs significantly faster than in the first one. This was interpreted as a result of greater delocalization of electrons in the 20-electron complexes of iron compared to the 19-electron complexes.     

Molecular Profiling of a 6-Hydroxydopamine Model of Parkinson’s Disease

Convection enhanced delivery of 6-hydroxydopamine (6-OHDA) to the rat striatum results in a model of Parkinson’s disease. An important feature of this unilateral model is the progressive loss of dopaminergic (DA) neurons over the course of several weeks. To improve the understanding of this model, gene expression changes in the substantia nigra, which contains the DA neuron cell bodies, and the striatum, which contains the DA neuron synaptic terminals, were examined using DNA microarrays. Samples were collected and behavior was analyzed from vehicle and toxin treated animals at 3 days, 1 week, 2 weeks and 4 weeks following 6-OHDA treatment. Tissue DA content was determined and samples from animals which exhibited a substantial depletion of striatal DA were included in the subsequent gene expression analysis. The results of the gene expression analysis indicated that 6-OHDA elicits a vigorous inflammatory response, comprised of several distinct pathways, in the striatum at the earliest time point tested. In contrast, relatively few gene expression changes were observed in the SN at the 3-day time point. In both tissues examined there was evidence for a vigorous inflammatory response at the 1- and 2-week time points, which was substantially diminished by the 4-week time point. Inflammation plays a prominent role in the 6-OHDA model of Parkinson’s disease.     

Bioconversion of the sodium salt of Simvastatin (MK-733) to 6-desmethyl-6-α-hydroxymethyl Simvastatin

Summary An actinomycete (MA 6474, ATCC 53828) isolated from a soil sample (Mutare, Zimbabwe) was found to biotransform the sodium salt of Simvastatin (MK-733) to 6--hydroxymethyl MK-733, 6--hybroxymethyl MK-733, and 6-ring-hydroxy MK-733. The bioconversion efficiency to the desired compound, 6--hydroxymethyl MK-733, was enhanced by optimizing the physico-chemical parameters of the process. In shake flask cultures, addition of magnesium (0.125 mg/l Mg SO₄·7H₂O) to the medium resulted in a five-fold increase in the rate of bioconversion to the diastereomer. The ratio of bioconversion products (6--hydroxymethyl, 6--hydroxymethyl, and 6-ring-hydroxy MK-733) was regulated by pH. Process improvements and scale up in 23-1 fermentors, which consisted of a controlled addition of substrate (MK-733), resulted in a 2-fold increase in alpha diastereomer Production (42 vs. 79 U/ml) and a 23-fold rate increase in the formation of -diastereomer. A high diastereomeric ratio (: =91) facilitated downstream processing.     

The antibacterial properties of 6-tuliposide B. Synthesis of 6-tuliposide B analogues and structure–activity relationship

6-Tuliposide B is a secondary metabolite occurring specifically in tulip anthers. Recently, a potent antibacterial activity of 6-tuliposide B has been reported. However, its molecular target has not yet been established, nor its action mechanism. To shed light on such issues, 6-tuliposide B and tulipalin B analogues were synthesized and a structure–activity relationship (SAR) was examined using a broad panel of bacterial strains. As the results of SAR among a total of 25 compounds, only tulipalin B and the compounds having 3′,4′-dihydroxy-2′-methylenebutanoate (DHMB) moieties showed any significant antibacterial activity. Moreover, the 3′R analogues of these compounds displayed essentially the same activities as 6-tuliposide B and the structure of the 3′R-DMBA moiety was the same as that of the proposed active moiety of cnicin. These results suggest that 6-tuliposide B has the same action mechanism as proposed for cnicin and bacterial MurA is one of the major molecular targets of 6-tuliposide B.     

The synthesis of 6-deoxy-6-fluoro-α,α-trehalose and related analogues

Selective acid-catalysed methanolysis of 2,3,2′,3′-tetra-O-benzyl-4,6:4′,6′-di-O-benzylidene-α,α-trehalose yielded the monobenzylidene derivative, which was converted into the 4,6-dimesylate. Selective nucleophilic displacement of the primary sulphonyloxy group then gave 2,3-di-O-benzyl-6-deoxy-6-fluoro-4-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-d-glucopyranoside. Removal of the protecting groups then yielded 6-deoxy-6-fluoro-α,α-trehalose. In addition, 6-deoxy-6-fluoro-4-O-mesyl-α,α-trehalose and a derivative of 4-chloro-4,6-dideoxy-6-fluoro-α-d-galactopyranosyl α-d-glucopyranoside were also prepared from the same substrate. Iodide displacement of 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranoside afforded the 6-iodide and 6,6′-di-iodide in yields of 31 and 36%, respectively. Similarly, the 6-azide and 6,6′-diazide were isolated in yields of 17 and 21%, respectively.     

Atherogenic effects of TNF-α and IL-6 via up-regulation of scavenger receptors

Patients with chronic inflammatory disorders such as rheumatoid arthritis (RA) have a high risk of developing cardiovascular disease. We evaluated the effects of TNF-α and IL-6 on foam cell formation, a pivotal process in atherogenesis. Accumulation of intracellular oxidized LDL (oxLDL) was induced when THP-1/macrophages were stimulated with TNF-α or IL-6. TNF-α induced the expressions of scavenger receptors SR-A and LOX-1, and IL-6 induced SR-A expression. Inhibition of the NF-κB signaling markedly decreased TNF-α-induced foam cell formation and SR-A expression. Serum from RA patients, but not healthy subjects, induced foam cell formation, which was partially reversed by either IL-6 or TNF-α blockade in conjunction with inhibiting the induction of scavenger receptors. The present study clearly showed that in patients with chronic inflammation mediated by TNF-α and IL-6, these cytokines are directly implicated in atherosclerotic plaque formation.     

Effects of integrin α6β1 on migration of hepatocellular carcinoma cells

In this study, we applied specific blocking antibodies for integrin α6 or β1 subunit, and evaluated the in vitro effects of integrins α6β1 on the adhesion, chemotaxis and migration of hepatocellular carcinoma (HCC) cell line SMMC-7721 to type IV collagen. The adhesion force and cell migration, as measured by a micropipette aspiration system and Boyden chamber assay respectively, was dramatically reduced when either integrin subunits was blocked. The chemotaxis, as determined using a dual-micropipette system, was only affected by the antibody against β1 subunit. This study suggests that integrin α6β1 is an important cell surface receptor that mediates the adhesion of SMMC-7721 to type IV collagen. But the α6 subunit has minimal effect on pseudopod formation in response to type IV collagen. Therefore, the integrin α6β1-mediated cell migration is, at least in part, through the regulation on the cell adhesion step.