DHAP Synthesis from Rac-Glycidol

FruA is stereoselective and stereocenter 2 is created with the S onfiguration. Taking into account this stereoselectivity, the Nuclear Overhauser Effects (NOEs) observed, and the coupling constants measured, the configurations found for compound 11 were IS, 2S, 3R, and 6R. AH the substituents are equatorially positioned on the cyclohexane ring. The (2S,3R)-configurations are consistent with the usually observed diastereoselectivity of FruA In a second exploration [20], the racemic aldehyde 10 was condensed with DHAP after ketal hydrolysis of rac-14 under acidic conditions. In this case, two major isomers 12 and 13 were isolated in 35 and 29% yields after flash chromatography purification. 

When an optically pure compound (R)-14 was used only one isomer 13 was isolated in a 50% yield. 

Opening a new route to valiolamine analogs, this work broadens the scope of the enzymatic aldol reaction combining in one pot the formation of two carbon-carbon bonds with high stereoselectivity. We demonstrate a short efficient synthesis of new nitro- and aminocychtols that considerably reduces the laborious 

Halo-sugars are very useful building blocks for designing further reactions by substitution of halogen atoms. From these compounds, we have developed a che-moenzymatic strategy giving 5-thio-D-xylose in four steps (the key step being catalyzed by FruA). 

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