A New Method To Convert the Fischer Projection of a Monosaccharide to the Haworth Projection

This method is based upon the R,S-configuration designation of each asymmetric carbon of a monosaccharide. According to the rule of configurational retention of each original asymmetric carbon, the Fischer projection of a monosaccharide can be converted into different views of the Haworth projection (the carbon-numbering orientation of the Haworth ring can be in either a clockwise or a counterclockwise direction, and the oxygen atom can be written at any corner of the ring). The d,l-configuration of a sugar in Haworth projection can be directly determined by designating the R,S-configuration of the highest-numbered asymmetric carbon; that is, the most distant carbon from the anomeric carbon. The R-configuration at this carbon corresponds to the d-family, and S- to the l-family. By comparing the stereochemistry of the anomeric carbon with that of the highest-numbered asymmetric carbon, the α,β-anomer of a Haworth projection is directly notated. If these two carbons have the same configuration (R,R or S,S), the anomer is β; if different (R,S or S,R), the anomer is α. This method proves to be general and widely applicable.