Decarbonylation of Unprotected Aldose Sugars by Chlorotris(triphenylphosphine)rhodium(I). A New Descent of Series Approach to Alditols, Deoxyalditols, and Glycosylalditols

Article abstract of DOI:10.1021/jo00283a017

Unprotected Cn aldose sugars are cleanly decarbonylated by 1 equiv of chlorotris(triphenylphosphine)rhodium(I) in 1-24 h at 130 deg C in N-methyl-2-pyrrolidinone solution to give the corresponding Cn-1 alditol in about 75-95percent yields.This technique represents a useful variation on traditional carbohydrate "descent of series" reactions.The procedure is quite general and also works on a number of aldose derivatives, such as deoxy sugars, N-acetylated amino sugars, and disaccharides, providing convenient small-scale syntheses of deoxyalditols, (acetylamino)deoxyalditols, and glycosylalditols, respectively.The reactions proceed with complete retention of stereochemistry, the only side products observed being a few percent of the Cn lactones and the Cn-2 alditol.Attempts to make the reactions catalytic have not yet been very successful.