Extending the scope of the Ferrier reaction: fragmentation-rearrangement reactions of selectively substituted 1,2-cyclopropanated glucose derivatives

Two further variations of the Ferrier-type allylic rearrangements of 1,2-cyclopropanated glucose derivatives bearing an acetoxylated carbon at the 1′-position are described. In the first, treatment of the cyclopropanated sugar with a nucleophile (ROH, PhSH, azide) and Lewis acid (BF3·Et2O or Al(OTf)3), gives 2-C-vinyl glucosides in good yields and α-selectivities. Alternatively, treatment with a combination of Lewis acid and acetic acid leads to a novel fragmentation-rearrangement to form a 2,3-dehydro-2-formyl-C-glycoside. Figure optionsDownload as PowerPoint slide

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► 1,2-Cyclopropanated glucose bearing an ester is unreactive with Lewis acids.
► Reduction and acetylation gives the corresponding cyclopropylcarbinyl acetate.
► This undergoes facile Ferrier-type rearrangement to give 2-C-vinyl glucosides.
► Analogous secondary acetates formed from the ester lead to C-2 alkenylated sugars.
► A novel Ferrier-type rearrangement to unsaturated 2-C-formyl glucose is described.