No abstract

Automated synthesis of DNA, RNA, and peptides provides quickly and reliably important tools for biomedical research. Automated glycan assembly (AGA) is significantly more challenging, as highly branched carbohydrates require strict regio- and stereocontrol during synthesis. A new AGA synthesizer enables rapid temperature adjustment from −40 to +100 °C to control glycosylations at low temperature and accelerates capping, protecting group removal, and glycan modifications using elevated temperatures. Thereby, the temporary protecting group portfolio is extended from two to four orthogonal groups that give rise to oligosaccharides with up to four branches. In addition, sulfated glycans and unprotected glycans can be prepared. The new design reduces the typical coupling cycles from 100 to 60 min while expanding the range of accessible glycans. The instrument drastically shortens and generalizes the synthesis of carbohydrates for use in biomedical and material science.

Glycosidic bond formation is a continual challenge for practitioners. Aiming to enhance the reproducibility and efficiency of oligosaccharide synthesis, we studied the relationship between glycosyl donor activation and reaction temperature. A novel semi‐automated assay revealed diverse responses of members of a panel of thioglycosides to activation at various temperatures. The patterns of protecting groups and the thiol aglycon combine to cause remarkable differences in temperature sensitivity among glycosyl donor building blocks. We introduce the concept of donor activation temperature to capture experimental insights, reasoning that glycosylations performed below this reference temperature evade deleterious side reactions. Activation temperatures enable a simplified temperature treatment and facilitate optimization of glycosyl donor usage. Isothermal glycosylation below the activation temperature halved the equivalents of building block required in comparison to the standard “ramp” regime used in solution‐ and solid‐phase oligosaccharide synthesis to‐date.

We present and analyze comprehensive measurements of the evaporation behavior, E, of a thinning liquid film during a hydrodynamic-evaporative spin coating experiment. E, (the rotation speed), and (the liquid viscosity) are the main control parameters of the process. The entire film thinning process can be described theoretically quite well if these parameters are known. Values of are easily accessible in advance (calculations, literature values, measurements). Values for E can essentially not be found in the literature. They are hard to measure and specific for the experimental conditions. There is also no generally accepted strategy to calculate E. Our experimental results are compared with a theoretical prediction for E based on ideas by Bornside, Macosco, and Scriven, which were presented long ago. Their approach was never tested experimentally. Theory and experiment agree well for many solvents and different . This approach permits in advance the quantitative calculation of the evolution of the entire hydrodynamic-evaporative film thinning process. We also derive a general formula to predict ab initio, with literature data only, the amount of final deposit (film thickness) of solute in the case of spin coating mixtures of volatile solvents and nonvolatile solutes. K E Y W O R D Sevaporation, final deposition, final film thickness, spin casting, spin coating, thin liquid films INTRODUCTIONSpin coating is widely used in research and in industrial applications to prepare thin planar films on substrates. 1 In the process, a small amount of liquid is deposited on a rotating planar substrate and spread into a planar film by centrifugal forces. The liquid may be a melt or a solution. Here we will focus on hydrodynamic-evaporative spin coating, that is, spin coating of mixtures of volatile solvents and nonvolatile solutes. After evaporation of the volatile components, this process results in the deposition of a thin film of mainly solute. 2 Typically this solute film is the main purpose of the process. The thickness of the solute film (the solute coverage) can be adjusted through the process parameters. The most relevant parameters are: (1) the liquid viscosity, 3 (2) the solute concentration, 4 (3) the rotation speed, 5,6 and (4) the evaporation behavior of the liquid. 2,[7][8][9] This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.