Stereoselective C-glycoside formation by a rhodium(I)-catalyzed 1,4-addition of arylboronic acids to acetylated enones derived from glycals.

[reaction: see text] A new method for the formation of C-glycosides has been developed employing a cationic rhodium(I)-catalyzed 1,4-addition of arylboronic acids to enones derived from glycals. The reaction is stereoselective for the alpha-anomer and is highly dependent on the nature of the rhodium catalyst.