Takeo Konakahara

Preparation and surface properties of silica-gel coating films containing branched-polyfluoroalkylsilane

Abstract Composite coating films crack-free and with smooth surfaces have been prepared by the sol–gel technique using branched chain polyfluoroalkylsilane (triethoxy[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl]silane) (D3Et) and tetraethoxysilane (TEOS) as starting materials. Surface properties of the fluorinated coating films heated at various temperatures were examined in comparison with films derived from methyltrimethoxysilane (MTM) and TEOS, based on the measurements of infra-red spectra, thermal gravimetric changes and X-ray photoelectron spectra and contact angle of water and diiodo methane. It was found that the fluorosilane-containing films had thermal stability and surface energies, γ s , as small as polytetrafluoroethylene (PTFE) up to 400°C and a large contact angle of water comparable to the films derived from MTM and TEOS. Large hydrophobicity of fluorosilane-containing films seems to be due to the dispersion component of the surface energy compared with methyltrimethoxysilane and TEOS films. We conclude from X-ray photoelectron spectra measurements that the surface energy of the fluorinated coating film originate from polyfluorocarbon molecules at the topmost film surface.

Synthesis of a novel lipopeptide with α-melanocyte-stimulating hormone peptide ligand and its effect on liposome stability

Introduction of liposomes into target cells is important for drug delivery systems. For this purpose, the surface of the liposome is equipped with ligand peptides, which may bind to specific receptors on the cell membrane. An artificial novel lipopeptide (MSH-C4A2) containing the α-melanocyte-stimulating hormone (α-MSH) sequence and two long alkyl chains was designed and synthesized, and the liposome, composed of egg phosphatidylcholine (EPC) and MSH-C4A2, was prepared. The stability of the liposome was estimated by measuring calcein leakage from the liposome inner phase. The stability of the liposome decreased upon addition of MSH-A4C2, which seemed to be attributable to the amphiphilic property of the peptide moiety (α-MSH) of MSH-A2C4. The stability was, however, recovered fairly well upon addition of cholesterol (Ch) or phosphatidylglycerol (PG). It was concluded therefore that the ternary system, MSH-C4A2/Ch/EPC or MSH-C4A2/PG/EPC, is suitable for preparing the functional liposome.

Preparation of branched-polyfluoroalkylsilane-coated silica gel columns and their HPLC separation characteristics

SummaryThe conditions for reaction of the branched polyfluoroalkylsilane D3CL with silica gel have been examined. From elemental analyses and29Si NMR spectra it was found that the surface coverage and endcapping of D3CL-coated silica gel (Fluofix®) were the same as for ODS packings.The separation behavior of these phases was compared that of a variety of other packings. For polyaromatic compounds and benzene derivatives Fluofix worked in the reversed-phase mode and its retention characteristics were similar to those of C1 or CN packings. For fluorinated compound the retention characteristics of the phases is similar to those of ODS although with MeOH-water and MeCN-water mobile phases the pressure loss was lower for the fluorinated phases than for ODS.

An effective synthesis of N-substituted 2-sulfenamoylbenzoates and 1,2-benzisothiazolin-3-ones that uses 1,2-benzisothiazolin-3-one as a leaving group

N-Substituted 2-sulfenamoylbenzoates and 1,2-benzisothiazolin-3-ones were effectively synthesized by the substitution reaction between S-[2-(3-oxo-1,2-benzisothiazolinyl)]-2-mercaptobenzoates (2) and primary amines. The substitution reaction occurred on the sulfur atom of the 2-sulfenamoyl group of 2, and 1,2-benzisothiazolin-3-one behaved as a leaving group. The eliminated 1,2-benzisothiazolin-3-one could be reused as a starting material for the synthesis of 2. N,N-Disubstituted 2-sulfenamoylbenzoates were prepared by the reaction of 2 with secondary amines.

Preparation of functional liposomes with peptide ligands and their binding to cell membranes

Two novel lipopeptides, which have the peptide ligands [α-melanocyte stimulating hormone (α-MSH)] sequence and repeated [Gly-Arg-Gly-Asp-Se (GRGDS) sequence[, are designed, synthesized by the solid-phase method, and introduced into liposome membranes by the freeze-thaw method. These liposomes bearing the peptide ligands on their surface are expected to bind to cell membranes. We have confirmed that the lipopeptides are introduced into liposome membranes almost quantitatively, while such a high degree of incorporation has not been accomplished in conventional methods. In this respect, the present method is superior to prepare surface-modified liposomes that are applicable to drug carriers and so on. We have also confirmed by using immunoelectron microscopy that the peptide ligands are actually located in an aqueous phase. It has been shown by flow cytometry that the liposome bearing α-MSH peptide ligand binds to B16 cells and the liposome bearing the repeated GRGDS sequence binds to NIH3T3 cells.

Simultaneous separation of nonionic surfactants and polyethylene glycols by reversed phase high performance liquid chromatography

SummaryThe simultaneous separation of polyethylene glycol and its derivatives such as the lauryl alcohol and lauric acid ethoxylate oligomers was carried out by reversed phase high performance liquid chromatography. Branched fluorinated silica gel columns combined with evaporative light scattering detection were used for the characterization of nonionic surfactants. Lauryl alcohol ethoxylate oligomers were separated at 10°C with an isocratic eluent according to ethoxylate number and the retention time of the oligomers decreases with increasing ethoxylate number. The Van’t Hoff plots of retention factor of lauryl alcohol ethoxylate gave a complex cure, which is anomalous behavior for reversed phase high performance liquid chromatography. The anomalous Van’t Hoff plots were explained by a partial conformational change from polar to less polar conformers with increasing temperature. The most significant features for the analysis of the lauryl alcohol ethoxylate were the use of acetonitrile as mobile phase and operating temperature. The polyethylene glycol was separated according to ethoxylate number and the retention time of oligomers increased with increasing ethoxylate number. The Van’t Hoff plots of retention factor of polyethylene glycol had negative slopes. It was presumed that the polar conformation of the ethylene oxide chain decreased with increasing temperature. The lauryl alcohol ethoxylate and polyethylene glycol were separated simultaneously in gradient elution as a result of the conformational change of the ethylene oxide chain. As a practical example, lauric acid ethoxylate simultaneously separated into free polyethylene glycol, ethoxylate monolaurate and ethoxylate dilaurate in gradient elution.

Stereospecific synthesis of (E)-alkenylpyridines via α-silyl carbanion

Abstract (E)-2-Alkenylpyridines were stereospecifically prepared from 2-(trimethylsilylmethyl)pyridine and the corresponding (E)-aldimines of anilines by an analogous reaction to the Peterson reaction.

Syntheses of branched-polyfluoroalkylsilanes

Abstract Three types of branched-type polyfluoroalkylsilanes, trichloro[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl] silane (D3CL3), monochlorodimethyl[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl]silane (D3CL), triethoxy[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl]silane (D3Et3), could be synthesized using the hydrosilylation reaction of the branched-type polyfluoroalkene and corresponding silanes in the presence of hydrogen hexachloroplatinate (IV) as a catalyst. The hydrosilylation reaction of 4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoro-1-heptene with silanes produced only β-addition compounds highly regioselectively. From the MM2 calculation, it was found that the branched-polyfluoroalkylsilane has a bent structure at quaternary carbon.