Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

Wünsch M, Schröder DC, Fröhr T, et al. Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics. Beilstein Journal of Organic Chemistry. 2017;13:2428-2441.The amide moiety of peptides can be replaced for example by a triazole moiety, which is considered to be bioisosteric. Therefore, the carbonyl moiety of an amino acid has to be replaced by an alkyne in order to provide a precursor of such peptidomimetics. As most amino acids have a chiral center at C-alpha, such amide bond surrogates need a chiral moiety. Here the asymmetric synthesis of a set of 24 N-sulfinyl propargylamines is presented. The condensation of various aldehydes with Ellman's chiral sulfinamide provides chiral N-sulfinylimines, which were reacted with (trimethylsilyl) ethynyllithium to afford diastereomerically pure N-sulfinyl propargylamines. Diverse functional groups present in the propargylic position resemble the side chain present at the Ca of amino acids. Whereas propargylamines with (cyclo) alkyl substituents can be prepared in a direct manner, residues with polar functional groups require suitable protective groups. The presence of particular functional groups in the side chain in some cases leads to remarkable side reactions of the alkyne moiety. Thus, electron-withdrawing substituents in the C-alpha-position facilitate a base induced rearrangement to alpha, beta-unsaturated imines, while azide-substituted propargylamines form triazoles under surprisingly mild conditions. A panel of propargylamines bearing fluoro or chloro substituents, polar functional groups, or basic and acidic functional groups is accessible for the use as precursors of peptidomimetics

A method for joining polymers and metals or polymers and ceramics

A recently developed laser fusion technique allows polymers to be attached to metals and ceramics in short cycle times. The process and its capabilities are reviewed together with its growing range of applications

Laser-beam helical drilling of high quality micro holes

A large variety of modern components and products such as fuel injectors and spinning nozzles require holes drilled to very high standards as fare as roundness, diameter and aspect ratio are concerned. Laser-beam helical drilling has shown great promise to produce such high quality micro holes. In helical drilling, the laser beam is rotated relative to the work piece. In this case, the rotational movement is produced using a Dove prism, mounted in a high speed, hollow shaft motor. Different kind of holes are drilled and investigated with respect to hole-quality and drilling time

Ablation of PEDOT/PSS with excimer lasers for micro structuring of organic electronic devices

In this paper we present a potentially fast method for high resolution micro structuring of organic electronics via laser patterning. An investigation of the absorption spectrum in the UV/VIS regime of poly (3,4-ethylene dioxythiophene) poly (styrene-sulfonate) (PEDOT/PSS) has shown that UV-laser radiation should be used for optimal laser ablation of the material. Hence, the ablation characteristics of PEDOT/PSS with two different excimer lasers are compared with each other. The optimal fluence for the ablation of the material has been determined. The lasers used in this study are ArF ( = 193 nm) and KrF ( = 248 nm) excimer lasers

Stability limits of laser drilled hole arrays on large areas

Large area microdrilling utilizing short pulsed solid state lasers is a promising manufacturing technique for filtration technology. High degree of perforation and high quality of the drilled hole arrays regarding roundness and diameter variation of holes are the main challenges. The goal is to achieve a high degree of perforation with a high number of round holes on a constant pitch. The resulting variation of hole roundness and mechanical stability limitations of the percussion drilled foil using a ns pulsed laser source with a wavelength of 355 nm when drilling a 50 µm thin aluminum foil are presented here. Different drilling strategies are investigated in relation to roundness, hole diameter, and heat propagation. The quality of drilled holes decreases with decreasing pitch and hole diameter. This can be related to thermal effects and pointing stability of the laser beam. Both effects are directional in the setup used here and can, therefore, be superposed positively or negatively. Due to adapted superposition of the effects, the roundness of the holes can be maximized

Stability limits of laser drilled hole arrays on large areas

Large area microdrilling utilizing short pulsed solid state lasers is a promising manufacturing technique for filtration technology. High degree of perforation and high quality of the drilled hole arrays regarding roundness and diameter variation of holes are the main challenges. The goal is to achieve a high degree of perforation with a high number of round holes on a constant pitch. The resulting variation of hole roundness and mechanical stability limitations of the percussion drilled foil using a ns pulsed laser source with a wavelength of 355 nm when drilling a 50 µm thin aluminum foil are presented here. Different drilling strategies are investigated in relation to roundness, hole diameter, and heat propagation. The quality of drilled holes decreases with decreasing pitch and hole diameter. This can be related to thermal effects and pointing stability of the laser beam. Both effects are directional in the setup used here and can, therefore, be superposed positively or negatively. Due to adapted superposition of the effects, the roundness of the holes can be maximized