Silicon Effect on the Enantioselective Transcyanation of Acetyltrimethylsilane Examined by Different Oxynitrilases

The synthesis of optically active （R）- and （S）-2-trimethylsilyl-2-hydroxyl propionitrile by enantioselective transcyanation of acetyltrimethylsilane with acetone cyanohydrin was successfully carded out using defatted plum, loquat , peach, almond or apple seed meals as （R）-oxynitrilase source and using Manihot esculenta leaves as （S）-oxynitrilase source in a biphasic system with good conversion and high enantiomeric excess. Comparative study demonstrated that silicon atom in substrate showed great effect on the reaction and due to the unique characteristics of silicon atom, both the substrate conversion and the product e.e. of the transcyanation of acetyltrimethylsilane were much higher than those of its carbon counterpart 3,3-dimethyl-2-butanone for all examined oxynitrilases.

Kinetic Model of Resin-Catalyzed Decomposition of Acetone Cyanohydrin in Organic Solvent

Decomposition of acetone cyanohydrin is the first-step reaction for preparing (S)-α-cyano-3-phenoxybenzyl alcohol (CPBA) by the one-pot method in organic media. Considering the compatibility of biocatalysts with chemical catalysts and the successive operation in the bioreactor, anion exchange resin (D301) was used as catalyst for this reaction. External diffusion limitation was excluded by raising rotational speed to higher than 190r·min^-1 in both solvents. Internal diffusion limitation was verified to be insignificant in this reaction system. The effect of acetone cyanohydrin concentration on the reaction was also investigated. An intrinsic kinetic model was proposed when the mass transfer limitation was excluded, and the average deviation of the model is 10.5%.

Synthesis and Crystal Structure of 2-Amino-1, 1-diferrocenylethanol

Amino-1,1-diferrocenylethanol 2 was prepared by reduction of trimethylsilyl cyanohydrin ether of diferrocenyl ketone. The crystal structure of 2 was further defined by X-ray diffraction.

Karrikin and Cyanohydrin Smoke Signals Provide Clues to New Endogenous Plant Signaling Compounds

Two new types of signaling compounds have been discovered in wildfire smoke due to their ability to stimulate seed germination. The first discovered were karrikins, which share some structural similarity with the strigol- actone class of plant hormones, and both signal through a common F-box protein. However, karrikins and strigolactones operate through otherwise distinct signaling pathways, each distinguished by a specific a/13 hydrolase protein. Genetic analysis suggests that plants contain endogenous compounds that signal specifically through the karrikin pathway. The other active compounds discovered in smoke are cyanohydrins that release germination-stimulating cyanide upon hydrolysis. Cyanohydrins occur widely in plants and have a role in defense against other organisms, but an additional role in endogenous cyanide signaling should also now be considered.

Enzymatic Enantioselective Synthesis of (R)-2-Trimethylsilyl-2-hydroxyl-propionitrile by Defatted Apple Seed Meal

The enantioselective synthesis of ( R ) 2 trimethylsilyl 2 hydroxyl propionitrile by ( R ) oxynitrilase contained in defatted apple seed meal in a biphasic system was successfully performed. The influences of some factors on the reaction were investigated systematically. Diisopropyl ether was found to be the best for this reaction among all the organic solvents examined. The optimal concentration of defatted apple seed meal, aqueous phase content, concentrations of acetyltrimethylsilane and acetone cyano^hydrin, buffer pH, reaction temperature were 4% ( W/V ), 23% ( V/V ), 20 mmol·L -1 , 40 mmol·L -1 , pH=5 0 and 40 ℃, respectively, under which the initial reaction rate, substrate conversion and product enantiomeric excess were 9 4 mmol·L -1 ·h -1 , 99% and >99%, respectively.

Stereoselective Synthesis of （R）-Salmeterol via Asymmetric Cyanohydrin Reaction

The authors described a short and highly enantioselective route to （R）-salmeterol involving asymmetric synthesis of cyanohydrin followed by nucleophilic substitution with 6-（4-phenylbutoxy） hexyl methanesulfonate.