Abstract: The invention pertains to a process for preparing a compound of formula (1) wherein R1 is independently chosen from C1-C6 alkyl, cycloalkyl, aralkyl and aryl, and R2, R3 and R4 are independently chosen from hydrogen and C1-C6 alkyl, cycloalkyl, aralkyl and aryl; which process comprises the steps of: a) contacting a compound of formula (2) wherein R1 and R2 are as above and M+ is a monovalent metal ion, with a compound of formula (3) wherein R3 and R4 are as above, to form a compound of formula (4) and b) followed by contacting the compound of formula (4) with an acid to give a compound of formula (1), wherein step (a) and/or step (b) are conducted in continuous mode.

Abstract: The invention pertains to a process for preparing a compound of formula (1) wherein R1 is independently chosen from C1-C6 alkyl, cycloalkyl, aralkyl and aryl, and R2, R3 and R4 are independently chosen from hydrogen and C1-C6 alkyl, cycloalkyl, aralkyl and aryl; which process comprises the steps of: a) contacting a compound of formula (2) wherein R1 and R2 are as above and M+ is a monovalent metal ion, with a compound of formula (3) wherein R3 and R4 are as above, to form a compound of formula (4) and b) followed by contacting the compound of formula (4) with an acid to give a compound of formula (1), wherein step (a) and/or step (b) are conducted in continuous mode.

Abstract: The invention relates to a method for carrying out reactions with participation of carbocations, whereby the initial most strongly exothermic phase of the reaction is carried out at high temperature (60 to 120° C.) and short residence time (1 to 30 seconds) in a microreactor and the subsequent less exothermic phases are carried out at optionally lower temperatures in two or more residence time units with longer residence times (1 to 30 seconds).

Abstract: New genes containing a DNA sequence coding for hydroxynitrile lyase, which genes can be prepared via a primer combination based on the DNA sequence of the 5?-region of the mdl genes from the Prunus serotina and from Prunus amygdalus and/or a primer 2 based on the 3?-region of the DNA sequences of one of the hydroxynitrile lyase isoenzymes from Prunus serotina or from Prunus amygdalus, subsequent amplification with a DNA polymerase using a DNA from organisms, containing genes coding for hydroxynitrile lyase, as templates and cloning, and also recombinant proteins which can be prepared in suitable host cells by heterologous expression of the DNA sequence of said HNL genes, and proteins and fusion proteins derived therefrom and use of said proteins for preparing (R)- or (S)-cyanohydrins.

Abstract: New genes containing a DNA sequence coding for hydroxynitrile lyase, which genes can be prepared via a primer combination based on the DNA sequence of the 5?-region of the mdl genes from Prunus serotina and from Prunus amygdalus and/or a primer 2 based on the 3?-region of the DNA sequences of one of the hydroxynitrile lyase isoenzymes from Prunus serotina or from Prunus amygdalus, subsequent amplification with a DNA polymerase using a DNA from organisms, containing genes coding for hydroxynitrile lyase, as templates and cloning, and also recombinant proteins which can be prepared in suitable host cells by heterologous expression of the DNA sequence of said HNL genes, and proteins and fusion proteins derived therefrom and use of said proteins for preparing (R)- or (S)-cyanohydrins.

Abstract: Process for the preparation of optically highly pure (R)- and (S)-&agr;-hydroxycarboxylic acids, in which either isolated, impure (R)- and (S)-&agr;-hydroxycarboxylic acids prepared by acidic hydrolysis of the (R)- and (S)- cyanohydrins obtained by enzyme-catalyzed addition of a cyanide group donor to the corresponding aldehydes or ketones are recrystallized in an aromatic hydrocarbon, optionally in the presence of a cosolvent, and optically highly pure (R)- and (S)-&agr;-hydroxycarboxylic acids having an optical purity of over 98%ee are obtained or the hydrolysis solution obtained by acidic hydrolysis of the (R)- and (S)-cyanohydrins is treated directly with an aromatic hydrocarbon, optionally in combination with a cosolvent, and is then extracted at hydrolysis temperature, whereupon after cooling of the organic phase the corresponding chemically and optically highly pure (R)- and (S)-&agr;-hydroxycarboxylic acids having an optical purity of over 98%ee crystallize out.

Abstract: The invention relates to the production of (R)-enantiomeric, optically active cyanohydrins by reacting an aldehyde or a ketone with a cyanide group donor in the presence of (R) oxynitrilase, wherein a reaction mixture comprising a) an aldehyde or a ketone dissolved in an organic solvent; said organic solvent is immiscible or only slightly miscible with water, b) any aqueous R)-oxynitrilase solution and c) a cyanide group donor is stirred in such away that an emulsion is formed which remains intact until the end of the enzymatic reaction. After the enzymatic reaction has terminated, the (R)-cyanohydrin is isolated from the reaction mixture.

Abstract: A process for the preparation of enantiomer-enriched aminofuranones and hydroxyfuranones in which an enantiomer-enriched cyanohydrin is acylated by an acylating agent, then cyclized at 40 to 90° C. in the presence of zinc or a zinc compound to the corresponding enantiomer-enriched aminofuranone, which is converted where appropriate by acid hydrolysis into the corresponding enantiomer-enriched hydroxyfuranone.

Abstract: Process for the stereoselective reduction of chiral &agr;- or &bgr;-keto esters which have a chiral center in the &ggr; position in an inert solvent at temperatures from −80 to +50° C. using a reductant obtained by reaction of NaBH4 and (D)- or (L)-tartaric acid, to give the corresponding diastereomeric hydroxy compounds in each case.

Abstract: Process for the preparation of the (S)-enantiomers of optically active cyanohydrins, in which a reaction mixture of a) an aldehyde or ketone dissolved in an organic, water-immiscible or slightly miscible diluent, b) an aqueous (S)-hydroxynitrile lyase solution and c) a cyanide group donor is stirred in such a way that an emulsion is formed which is maintained up to the end of the reaction by stirring.