Dynamic Kinetic Resolution of 2-Phenylpropanal Derivatives to Yield β-Chiral Primary Amines via Bioamination

The amination of racemic alpha-chiral aldehydes, 2-phenylpropanal derivatives, was investigated employing omega-transaminases. By medium and substrate engineering the optical purity of the resulting β-chiral chiral amine could be enhanced to reach optical purities up to 99% ee. Using enantiocomplementary w-transaminases allowed us to access the (R)- as well as the (S)-enantiomer in most cases. It is important to note that the stereopreference of the omega-transaminases found for alpha-chiral aldehydes did not correlate with the stereopreference previously observed for the amination of methyl ketones. In one case the stereopreference switched even upon exchanging a methyl substituent to a methoxy group

Glas. Teilprojekt 2: Untersuchungen zu Restaurierungs- und Konservierungsmaterialien fuer historische Glasfenster

SIGLEAvailable from TIB Hannover: F97B1771+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Process Investigations on the One-Pot Synthesis of Rifamycin S Avoiding Chlorinated Solvents

The facile synthesis of rifamycin S from rifamycin B, a member of the ansamycin family of antibiotics, via the oxidation of rifamycin B was developed. Currently on an industrial scale, this oxidation is performed using harsh pH conditions and chlorinated solvents. With the development of a suitable buffer/methanol system, a similar yield and space-time-yield in comparison to the current process can be obtained renouncing chlorinated solvents. Employment of methanol as a reaction medium in this process is crucial for attaining high yields under mild reaction conditions. With this method a space-time-yield of 189 g L^–1 h^–1 of rifamycin S was achieved in one step

Glas. Teilprojekt 1: Bestaendigkeitsuntersuchungen an Modellglaesern mittelalterlicher Zusammensetzung und Entwicklung eines einfachen Bewitterungs-Simulations-Verfahrens

SIGLEAvailable from TIB Hannover: F97B1770+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Dynamic Kinetic Resolution of 2-Phenylpropanal Derivatives to Yield beta-Chiral Primary Amines via Bioamination

International audienc

IspH protein of Escherichia coli: Studies on iron-sulfur cluster implementation and catalysis

The ispH gene of Escherichia coli specifies an enzyme catalyzing the conversion of 1-hydroxy-2-methyl-2-(E)-butenyl diphosphate into a mixture of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) in the nonmevalonate isoprenoid biosynthesis pathway. The implementation of a gene cassette directing the overexpression of the isc operon involved in the assembly of iron-sulfur clusters into an Escherichia coli strain engineered for ispH gene expression increased the catalytic activity of IspH protein anaerobically purified from this strain by a factor of at least 200. For maximum catalytic activity, flavodoxin and flavodoxin reductase were required in molar concentrations of 40 and 12 muM, respectively. EPR experiments as well as optical absorbance indicate the presence of a [3Fe-4S](+) cluster in IspH protein. Among 4 cysteines in total, the 36 kDa protein carries 3 absolutely conserved cysteine residues at the amino acid positions 12, 96, and 197. Replacement of any of the conserved cysteine residues reduced the catalytic activity by a factor of more than 70 000