Experimental and computational investigation of the unexpected formation of β-substituted polyoxygenated furans from conveniently functionalized carbohydrates

In the course of our current studies on the reactivity of alkylidenecarbenes, prepared with the trimethylsilylazide/Bu2SnO method, on conveniently functionalized alpha-cyanomesylates derived from D-allose, D-arabinose, and D-threose, we have observed the unexpected, but mechanistically interesting formation of enantiomerically beta-substituted polyhydroxylated furans. These compounds are the result of a series of cascade fragmentation reactions on unstable intermediates obtained during 1,5C-H insertion reactions from alkylidenecarbenes. The mechanism of the reaction has been investigated by computational methods using DFT analysis. (C) 2009 Elsevier Ltd. All rights reserved.