Editing Oxygen Out Of Carbohydrates

Biomass-derived sugars are highly anticipated as renewable replacements for fossil resources in the production of fuels and feedstock chemicals. One limitation is that chemists need to remove some or all of the oxygen from the sugars’ carbon framework, which is difficult to do selectively and without destroying valuable stereocenters. A research team led by Michel R. Gagné of the University of North Carolina, Chapel Hill, reports an approach that can edit out some C–O bonds and replace them with C–H bonds while preserving some C–O stereocenters (Nat. Chem. 2015, DOI: 10.1038/nchem.2277). The researchers had previously found that a boron Lewis acid catalyst, B(C₆F₅)₃, can activate a secondary silane hydride reductant, H₂Si(CH₂CH₃)₂, to completely deoxygenate sugars to alkanes. They are now able to control the extent of deoxygenation and control formation of linear, branched, or cyclic products by using various tertiary silanes, HSiR₃, (where R is methyl, ethyl, tert-butyl, or phenyl) under milder reaction conditions. “Access to these types of oxygenated chiral building blocks in only one or two chemical operations was simply not possible before this work,” writes Andrew McNally of Colorado State University in an accompanying perspective.