Protective reagents

Pentafluorophenyl derivatives have received wide application in biochemistry as highly selective and efficient protective reagents (for a review, see reference 148)... 

When a cell extract prepared from A. nicotianae FI1612 cells was stored without the addition of sulfhydryl-protecting reagents, 80% of the initial activity was lost after storage at 4°C for 4 days. The enzyme activity was stabilized... 

Evaporation of volatile byproducts and solvents is often used to obtain the solid metal nanoparticles. The residue may contain metal nanoparticles and protective reagents. When the nanoparticles are well protected by ligands or polymers, then the solid residues can be dispersed again without coagulation of the particles. When the nanoparticles are not well protected, however, the evaporation often results in aggregation of the nano-particles. 

Extraction by an organic solvent or water can be used to separate metal nanoparticles soluble in an organic solvent or water. This technique can be used only for the nanoparticles protected by organic ligands or pol5mers. The solubility of protecting reagents with the solvent is crucially important in this technique. 

Many oligomers with various functionalities have been prepared in our laboratory M). However, the amino terminated species has been studied most extensively due to its wide utility as a component of a large number of segmented copolymers (e.g. imides, amides, ureas, etc.). In order to prepare functional oligomers of this type, one must first prepare the disiloxane. One route to this was pointed out some years ago by Saam and Speier (28). They showed that it was possible to react allylamine with a protecting reagent such as hexa-... 

Fluid that is flushed from the capillary gap is collected in a waste tray beneath the slide-coverplate assemblies. This tray has a limited capacity and must be drained prior to a staining run. The entire slide-coverplate and reagent carousel area are enclosed within a Plexiglascover during operation, which protects reagents from laboratory conditions (temperature, humidity) and prevents inadvertent contact with the robotic pipet arm during movement. 

Halogenothiophenes are finding increasing application in the synthesis of pharmaceuticals and plant protection reagents, but efforts to devise methods that specifically introduce a halogen to an a- or a j3-position have not always been completely successful. 

A transhydrocyanation reaction catalyzed by / / I INI. on Celite was investigated by Hanefeld and co-workers [41]. To shift the unfavorable equilibrium, the reaction was coupled with an irreversible acylation step. Problems occurred due to hydrolysis of the acyl donor by the water needed for enzyme activity and subsequent deactivation of the / Ihl I N1. by the acid formed. In situ derivatization in the cyanohydrin synthesis catalyzed by PaHNL on Celite was investigated, and a one-pot chemoenzymatic synthesis of protected cyanohydrins was developed using ethyl cyanoformate as both HCN donor and protecting reagent [70]. 

T. Mukaiyama, M. Ohshima, and M. Murakami, 2-Benzyloxy-propene A novel protective reagent of hydroxyl groups, Chem Lett 265 (1984) T. Mukaiyama, M. Ohshima, H. Nagaoka, and M. Murakami, A novel acid-resistant acetal-type protective group for alcohols, Chem. Lett 615 (1984). 

Exercise 13-21 Devise a synthesis of 3-hexyn-1,6-diol from two-carbon compounds using the unsaturated cyclic ether, >, as a protecting reagent for hydroxyl... 

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