Biomedical subjects

William A Greenberg

Publications and source records attributed to William A Greenberg.

5 recordsLinked to original sources

PubMed2006

Evaluation of RNA-binding specificity of aminoglycosides with DNA microarrays.

We have developed methods for using DNA array technology to probe the entire transcriptome to determine the RNA-binding specificity of ligands. Two methods were investigated. In the first method, the RNA-binding aminoglycoside antibiotic tobramycin was covalently linked to magnetic beads. The beads were bound to human liver mRNA and washed, and specifically bound RNA was eluted, amplified, and analyzed with DNA array technology. A small number of genes were found to bind specifically to the tobramycin beads. In the second method, the aminoglycoside ligand was added directly to the array hybridization reaction, and the signal was compared with a control experiment in the absence of ligand. The aminoglycosides were found to interfere with a small percentage of all hybridization events. These methods differ from traditional DNA array experiments in that the readout is a direct measure of the interaction between mRNA and a ligand, rather than an indirect measure of effect on expression. We expect that the results will lead to the discovery of new aminoglycoside-binding RNA motifs and may also have relevance toward understanding and overcoming the side effects observed with these antibiotics in the clinic.

Animals↗

PubMed2005

Cycloaddition of delta2-thiazolines and acyl ketenes under acidic conditions results in bicyclic 1,3-oxazinones and not 6-acylpenams as earlier reported.

[reaction: see text] Optically active Delta(2)-thiazolines 4 were previously reported to react with acyl Meldrum's acid derivatives 5 under acidic conditions (HCl (g) in benzene) to stereoselectively give 6-acylpenams 1. Recently we have discovered that the structure elucidation of these compounds was incorrect. Thus, we report new data showing that instead of acyl beta-lactams, the optically active isomers 3R,9R-1,3-oxazinones 3a-g are obtained stereoselectively in 38-93% yields.

Bridged Bicyclo Compounds, Heterocyclic↗

PubMed2004

Development of an efficient, scalable, aldolase-catalyzed process for enantioselective synthesis of statin intermediates.

A process is reported for efficient, enantioselective production of key intermediates for the common chiral side chain of statin-type cholesterol-lowering drugs such as Lipitor (atorvastatin) and Crestor (rosuvastatin). The process features a one-pot tandem aldol reaction catalyzed by a deoxyribose-5-phosphate aldolase (DERA) to form a 6-carbon intermediate with installation of two stereogenic centers from 2-carbon starting materials. An improvement of almost 400-fold in volumetric productivity relative to the published enzymatic reaction conditions has been achieved, resulting in a commercially attractive process that has been run on up to a 100-g scale in a single batch at a rate of 30.6 g/liter per h. Catalyst load has been improved by 10-fold as well, from 20 to 2.0 wt % DERA. These improvements were achieved by a combination of discovery from environmental DNA of DERAs with improved activity and reaction optimization to overcome substrate inhibition. The two stereogenic centers are set by DERA with enantiomeric excess at >99.9% and diastereomeric excess at 96.6%. In addition, down-stream chemical steps have been developed to convert the enzymatic product efficiently to versatile intermediates applicable to preparation of atorvastatin and rosuvastatin.

Amino Acid Sequence↗

PubMed2002

An enzyme library approach to biocatalysis: development of nitrilases for enantioselective production of carboxylic acid derivatives.

The discovery, from Nature, of a large and diverse set of nitrilases is reported. The utility of this nitrilase library for identifying enzymes that catalyze efficient production of valuable hydroxy carboxylic acid derivatives is demonstrated. Unprecedented enantioselectivity and substrate scope are highlighted for three newly discovered and distinct nitrilases. For example, a wide array of (R)-mandelic acid derivatives and analogues were produced with high rates, yields, and enantiomeric excesses (95-99% ee). We also have found nitrilases that provide direct access to (S)-phenyllactic acid and other aryllactic acid derivatives, again with high yields and enantioselectivities. Finally, different nitrilases have been discovered that catalyze enantiotopic hydrolysis of 3-hydroxyglutaronitrile to afford either enantiomer of 4-cyano-3-hydroxybutyric acid with high enantiomeric excesses (>95% ee). The first enzymes are reported that effect this transformation to furnish the (R)-4-cyano-3-hydroxybutyric acid which is a precursor to the blockbuster drug Lipitor.

Aminohydrolases↗

PubMedDate not supplied

Solid-phase synthesis of nucleoside analogues.

The synthesis of a 25 000 member library of nucleoside analogues as discrete compounds in milligram quantities is described. The use of the Nanokan technology developed by IRORI (Discovery Partners International) together with macroporous solid support allowed us to develop a highly reliable and practical synthetic route for the high-throughput derivatization of both the pyrimidine and purine nucleoside scaffold. A 2',3'-acetal linkage of the scaffolds to the solid support proved to be stable enough for the chemical transformations employed, yet labile enough for mild cleavage conditions to yield final products in high purity. The publication represents an example for combining synthetic organic chemistry on advanced scaffolds with the latest technologies of combinatorial chemistry in order to provide both industrial and academic institutions with compounds in high number and quality, thereby accelerating the search for novel biological targets and drug development.

Combinatorial Chemistry Techniques↗