Joachim Weissmuller

Silicon-Modified Carbohydrate Surfactants I: Synthesis of Siloxanyl Moieties Containing Straight-chained Glycosides and Amides

New siloxanyl-modified carbohydrate surfactants of the amide and glycoside type have been synthesized by coupling between defined as well as higher-molecular-weight siloxanes and carbohydrate structures via spacers of different lengths and hydrophilic power. Linear and branched monohydrogen di-, tri-, tetra- and penta-siloxanes and polyhydrogen siloxanes as well as mono- and di-saccharide lactone structures have been found to be good starting materials for the synthesis of amides, often in quantitative yield, whereas glycosides had to be prepared in low-yield multistep sequences including protection/deprotection steps. Selected strategies were applied to polysiloxanes yielding quantitatively a broad variety of carbohydrate-modified comb-like structures. The new substances were characterized by means of 13 C NMR spectroscopy, GC, capillary GC, GC-MS coupling and elemental analysis.

Silicon‐Modified Carbohydrate Surfactants II: Siloxanyl Moieties Containing Branched Structures

Branched siloxanyl-modified carbohydrate surfactants have been synthesized by coupling mono-, di- and poly-functional siloxanes to carbohydrate units either via a branched spacer or by attaching a separate modifying element to a straight-chained structure. Hydrophilic as well as extremely hydrophobic elements have been incorporated successfully. Siloxanyl-modified carbohydrates bearing a secondary amino function were alkylated in regioselective reactions by different epoxides ranging from glycidol- to siloxanyl-modified allyl glycidyl ether derivatives. Alternatively, carbohydrate-modified piperazinyl structures yielded cyclic subunits after alkylation. Structures bearing two identical hydrophilic groups are accessible by alkylation of carbohydrate-modified bisamides. The derivatives synthesized were characterized by means of GC, NMR and elemental analysis.

Silicon-modified carbohydrate surfactants. VI: Synthesis of carbosilane, silane, polysilane and non-permethylated siloxane derivatives ; the wetting behaviour of epoxy-modified precursor liquids on non-polar surfaces

The synthesis of carbohydrate surfactants bearing carbosilane, silane, polysilane and non-permethylated siloxane moieties is described. These surfactants consist of three structural elements: (1) a silicon-containing moiety, (2) a spacer and (3) a carbohydrate unit. Additionally two different types of mixed structures have been synthesized: (a) single-chained carbosilane–siloxane surfactants and (b) double-chained combinations of carbo- silanes, silanes and siloxanes. The wetting behaviour of the key intermediates, the allyl glycidyl derivatives, has been investigated by static surface tension (γlv, σ) and wetting tension (γsv−γsl, α) measurements on a non-polar perfluorinated surface (FEP® plate). The contact angles obtained for these pure liquids are not a linear function of the surface tension but depend on the polarity of the substructures.

Silicon-modified carbohydrate surfactants. VIII. Equilibrium wetting of perfluorinated solid surfaces by solutions of surfactants above and below the critical micelle concentration-surfactant distribution between liquid-vapour and solid-liquid interfaces

For selected carbohydrate-modified Silicon surfactants of the siloxane, carbosilane, polysilane and silane type, the concentration dependences of the liquid/vapour and solid/liquid interfacial tensions under equilibrium conditions have been determined. Further, the Lifshitz–van der Waals and donor–acceptor contributions have been calculated. Below the critical micelle concentration (cmc) a steep increase in donor–acceptor contributions to both interfacial tensions was found. The Lifshitz–van der Waals contribution of the liquid/vapour interfacial tension shows a pronounced minimum. Calculations of the concentration-dependent surface coverage suggest that preferential adsorption to one of the interfaces does not take place. Copyright

Silicon‐modified carbohydrate surfactants IX: dynamic wetting of a perfluorinated solid surface by solutions of a siloxane surfactant above and below the critical micelle concentration

The dynamic wetting behaviour on a perfluorinated, low-energy solid has been investigated for a carbohydrate-modified phenylsiloxane surfactant. The surfactant concentration, the rate of interface generation and the [solid/liquid interface area] : [liquid/vapour interface area] ratio were varied systematically. Dynamic data for the liquid/vapour (γ Iv ) and solid/liquid (γ sl ) interfacial tension as well as their Lifshitz-van der Waals and donor-acceptor contributions were determined under strictly controlled conditions. Since γ sl reacts sensitively to variations of the surfactant concentration and the rate of interface generation, the covering of the liquid/nonpolar solid interface is assumed to be a spreading limiting factor. The corresponding γ lv values remain constant and close to those obtained under equilibrium conditions.

Chemistry, stereochemistry and biological properties of KWG 4168

KWG 4168 (8-tert-butyl-1,4-dioxaspiro[4,5]decan-2-ylmethyl(ethyl)(propyl)amine; proposed common name spiroxamine) is a new fungicide consisting of four biologically active isomers (two diastereomers, four enantiomers). The four isomers were separated by preparative HPLC on a chiral stationary phase. The diastereoisomers were synthesised from the corresponding chirally pure glycerol derivatives and were separated by preparative HPLC. COSY, HSQC and NOESY NMR spectroscopy were used to asign the configuration of the amino residue relative to the cyclohexyl ring. Studies of the activity against wheat powdery mildew, as well as the inhibition of sterol biosynthesis in fungi by the four stereoisomers, indicate the contribution of each isomer to the biological activity of spiroxamine.

Assignment of the stereochemistry of spiroxamine by two-dimensional NMR spectroscopy and stereoselective chemical synthesis†

Spiroxamine is a new powdery mildew fungicide in cereals consisting of four biologically active isomers (two diastereomers, four enantiomers). The four isomers were separated by preparative high‐performance liquid chromatography (HPLC) on a chiral stationary phase. At this stage it was not possible to assign their stereochemistry. Using stereoselective synthesis starting with the corresponding chirally pure glycerol derivates, the configuration at the asymmetric center, could be fixed. The resulting diastereomers were separated by preparative HPLC. Using COSY, HSQC and NOESY NMR spectroscopy it was possible to assign the configuration of the amino residue relative to the cyclohexyl ring. The 600 MHz 1H NMR spectra permitted a complete assignment of all proton signals. The stereochemical assignment is based on NOEs observed in the NOESY spectrum.