Total syntheses of (-)- and (+)-goniomitine

The Stille coupling reaction of 3-(benzyloxymethyl)-1-(tert-butyldiphenylsiloxy)ethyl-1-(tributylstannyl)allene with N-(tert-butoxycarbonyl)-2-iodoaniline directly produced the corresponding 2-vinylindole derivative, which was independently transformed into natural (-)-goniomitine and unnatural (+)-goniomitine via the cross-metathesis with chiral oxazolopiperidone lactams. The antiproliferative activity of the synthesized natural (-)-goniomitine in Mock and MDCK/MDR1 cells showed them to be more potent to retard cell growth than unnatural (+)-goniomitine.     

Derivatives Of α-Cyclodextrin and the Synthesis of 6-O-α-D-Glucopyranosyl-α-Cyclodextrin

Abstract

Regioselective silylation of α-cyclodextrin with tert-butyl-dimethylsilyl chloride in N, N-dimethylformamide in the presence of imidazole gave, in 75% yield, the hexakis(6-O-tert-butyldimethylsilyl) derivative 2, which was transformed into the hexakis(2,3-di-O-methyl, 6-O-methyl, 2,3-di-O-propyl, and 2,3-di-O-acetyl) derivatives. On methanesulfonylation and p-toluenesulfonylation, the hexakis(2,3-di-O-acetyl) derivative 16 afforded the hexakis(2,3-di-O-acetyl-6-O-methylsulfonyl 17 and 2,3-di-O-acetyl-6-O-p -tolylsulfonyl 18) derivatives, respectively. Nucleophilic displacement of 17 and 18 with iodide, bromide, chloride, and azide ions afforded the hexakis(6-deoxy-6-iodo 19, 6-bromo-6-deoxy, 6-chloro-6-deoxy, and 6-azido-6-deoxy) derivatives, respectively, of α-cyclodextrin dodeca-acetate. The hexakis (2, 3-di-O-acetyl-6-deoxy) derivative was prepared from 19. Selective glucosylation of 16 with 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl bromide under catalysis by halide ion, followed by removal of protecting groups, furnished 6-O-α-D-glucopyranosyl-α-cyclodextrin.     

Selective α-D-Galactosylation of Benzyl 4,6-O-Benzyhdene-β-D-Galacto-Pyranoside with 2,3,4,6-Tetra-O-Benzyl-α-D-Galactopyranosyl Bromide Under Catalysis by Halide Ion

Abstract

Selective glycosylation of benzyl 4,6-O-benzylidene-β-D-galacto-pyranoside (1) with 1.5 mole equivalent of 2,3,4,6-tetra-O-binzyl-α-D-galactopyranosyl bromide (2) catalyzed by halide ion gave the (1→2)-α-(5) and (l→3)-α-D-linked disaccharide (7) derivatives in 22 and 40% yields, respectively. The D-galactose unit at the reducing end of 2-O-α-D-galactopyranosyl-D-galactose [11) at equilibrium in D₂O was shown By ¹³C NMR spectroscopy to exist in the pyranose and furanose forms in the ratio of ～2:1.     

Organic Polymer-Silica Gel Hybrid: A Precursor of Highly Porous Silica Gel

In this article I describe two of our discoveries. The first is the preparation of a transparent solid material composed of an organic polymer and silica gel. A novel material called a “hybrid” has successfully been prepared by the sol-gel reaction of ethyl orthosilicate in the presence of an organic polymer consisting of repeating units having an N-alkylamide group. The molecular-level dispersion of the organic polymer in the framework of silica gel has been established, which is due to the hydrogen-bond interaction between the organic polymer and silanol group of silica gel. The second discovery is the preparation of porous silica gel, which has been achieved by calcination of the organic polymer-silica gel hybrid at 600°C. Pore sizes ranging from 10 to 20 Å have been attained. A method of controlling pore size has been proposed.     

Oxidative Coupling of Carbon Acid Compounds by Means of Ag2O

Transition-metal catalyzed coupling of carbanions by means of transition metal compounds has constituted a convenient method of the carbon-carbon bond formation in organic synthesis.¹ Recently, CuCl₂-promoted coupling of lithium enolates of ketones² and esters³ has been reported, which provides new routes to 1,4-diketones and succinate derivatives, respectively. Now we found that some carbon acids, such as acylacetate and monosubstituted malonate, were readily oxidatively dimerized by Ag₂O without intervention of their carbanions in dimethyl sulfoxide (DMSO) according to eq. 1.     

Tailoring the trajectory of cell rolling with cytotactic surfaces

Cell separation technology is a key tool for biological studies and medical diagnostics that relies primarily on chemical labeling to identify particular phenotypes. An emergent method of sorting cells based on differential rolling on chemically patterned substrates holds potential benefits over existing technologies, but the underlying mechanisms being exploited are not well characterized. In order to better understand cell rolling on complex surfaces, a microfluidic device with chemically patterned stripes of the cell adhesion molecule P-selectin was designed. The behavior of HL-60 cells rolling under flow was analyzed using a high-resolution visual tracking system. This behavior was then correlated to a number of established predictive models. The combination of computational modeling and widely available fabrication techniques described herein represents a crucial step toward the successful development of continuous, label-free methods of cell separation based on rolling adhesion.     

Spin wave and vortex excitations of superfluid 3He-A in parallel-plate geometry

Quantized vortices with half-integer circulation, which are forbidden from existing in a conventional superfluid because of the single valueness of the wave function, are theoretically predicted to exist in superfluid 3He-A if the order parameters l over and d over form l over perpendicular d over texture. To form the l over perpendicular d over texture, we confined the superfluid between parallel plates with a 12.5 microm gap and applied a magnetic field of H=26.7 mT perpendicular to the plates to take NMR and orient d over perpendicular to l over. NMR spectra exhibit a negative-shift peak which probes that the uniform l over perpendicular d over texture is realized in our cell and show a new satellite signal under rotation. The rotation dependence of the satellite signal is interpreted that a Fréedericksz transition of l over texture is induced by rotation above 1.0 rad/s and vortices start to appear above 1.8 rad/s.     

Rotaxane Synthesis by an End-Capping Strategy via Swelling Axle-Phenols

A method for rotaxane synthesis by enlargement of the size of the terminal phenol group of the axle component by aromatic bromination has been developed. This method may be regarded as an end-capping strategy involving the swelling of the phenol group at the axle terminal. The advantages of the present strategy include: ready availability of axle components with a variety of swelling precursors, wide product scope (19 examples given including a [3]rotaxane), mild conditions for the swelling process, rich potential for the derivatization of the brominated rotaxanes, and possible release of the axle component by degradative dethreading of the thermally stable brominated rotaxanes under the basic conditions.