Month: July 2010

Presidential Green Chemistry Awards: Codexis/Merck part 2

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Savile, Janey, Mundorff, Moore, Tam, Jarvis, Colbeck, Krebber, Fleitz, Brands, Devine, Huisman, and Hughes.  Biocatalytic Asymmetric Synthesis of Chiral Amines from Ketones Applied to Sitagliptin Manufacture.  Science, 2010, 329, 305-309. DOI: 10.1126/science.1188934.

Here’s a short follow-up on this previous post, which covered a biocatalytic reaction developed by Codexis to make the key intermediate in the synthesis of Merck’s drug montelukast (aka Singulair).  The 2010 Presidential Green Chemistry Awards were just announced, and the award for “Greener Reaction Conditions” went to Merck and Codexis for developing an enantioselective biocatalyst for the synthesis of sitagliptin, Merck’s blockbuster anti-diabetes drug (aka Januvia).  This work is also the subject of a recently-published Science paper from Merck and Codexis.

The paper describes the development of an enzyme-catalyzed replacement for the final reaction in the synthesis of sitagliptin, in which a ketone functionality is converted into an amine. Continue reading →

From Biomass to Commodity Chemicals

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“An efficient didehydroxylation method for the biomass-derived polyols glycerol and erythritol.  Mechanistic studies of a formic acid-mediated deoxygenation” Arceo, E.; Marsden, P.; Bergman, R. G.; Ellman, J. A. Chemical Communications, 2009, 23, 3357. 10.1039/b907746d

Scheme 1, Proposed Conversion of Biomass Into Value Added Chemicals

A major focus in the area of “green” methods development is the mild and selective removal of functionality from readily available bio-derived feed stocks.  Unlike petrochemical derived starting materials, the majority of biomass is highly oxygenated (think carbohydrates or lignin), and before the carbon embedded within this framework can be used for all-purpose chemical manufacturing the oxygen must be removed. Continue reading →

Do water fleas like the taste of nanoparticles?

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“Quantification of Water Solubilized CdSe/ZnS Quantum Dots in Daphnia magna” N. A. Lewinski, H Zhu, H J Jo, D. Pham, R R Kamath, C R Ouyang, C D Vulpe, V L Colvin, and R A Drezek. Environ. Sci. Technol. 2010, 1841-1846. 10.1021/es902728a

“Quantum Dot Weathering Results in Microbial Toxicity” S Mahendra, H Zhu, V L Colvin, P J Alvarez. Environ. Sci. Technol. 2008, 9424-9430. 10.1021/es8023385

Overview of the test subject, technique, and nanoparticles used in these experiments

The goal of green chemistry is to design chemicals and chemical processes which are inherently less toxic. For the emerging discipline of nanoscience, the potential toxicological properties remain largely unknown. That said I would like to discuss two related articles concerning the fate and toxicity of nanoparticles (NPs) in the aquatic environment. I like this set of articles because they are both simple, and yet give a hint of the complexities involved with understanding NP fate and toxicity. The more recent, examines the interaction between CdSe/ZnS NPs with Daphnia (a model species for aquatic toxicity). And the original article that drew my attention to this work concerned the same NP and studies the effect that chemical degradation has on NP toxicity. Continue reading →

Dioxygen Activation at Low-Valent Silicon

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Xiong, Yao, Muller, Kaupp, Driess. From silicon(II)-based dioxygen activation to adducts of elusive dioxasiliranes and sila-ureas stable at room temperature. Nature Chemistry 2010, 2, 577-580. DOI: 10.1038/nchem.666

Metal-free syntheses are currently under intense investigation as potentially cheaper and less-polluting alternatives to reactions involving stoichiometric or catalytic metals. In the Driess group’s recent contribution to Nature Chemistry, they report a silylene compound that activates O2, a biologically and industrially relevant reaction that tends to be associated with transition metals. In addition, they were able to isolate and crystallographically characterize the first dioxasilirane, the silicon-based analogue of the more familiar dioxirane reagents. Importantly, Driess’s dioxasilirane is capable of intramolecular O-atom transfer with the resulting silanone having the shortest silicon-oxygen bond reported to date.

Continue reading →