H O H—C-OH CH2 H—C-OH H—C-OH HC—OH HC—OH CHOO CHOO D-Ribose 2-Deoxy-D-ribose an aldopentose an aldopentose (c)
2.2 All the monosacchrides except dihydroxyacetone contain one or more asymmetric (chiral) carbon atoms 2.2.1 The configuration of an asymmetric carbon in an open chain monosacchride is usually indicated by the Fischer projection formulas(fig) 2.2.2 The carbon atoms of a sugar are numbered starting at the end nearest to the carbonyl group
2.2 All the monosacchrides except dihydroxyacetone contain one or more asymmetric (chiral) carbon atoms. 2.2.1 The configuration of an asymmetric carbon in an open chain monosacchride is usually indicated by the Fischer projection formulas (fig.) 2.2.2 The carbon atoms of a sugar are numbered starting at the end nearest to the carbonyl group
Mirror CHO CHO OH H OH CHoO CHoO Ball-and-stick models
CHO CHO H-C-OH HO-C-H CH,OH CHOH D-Glyceraldehyde L-Glyceraldehyde Fischer projection formulas CHO CHO H-C-OH HO-C-H CHOH CHOH D-Glyceraldehyde L-Glyceraldehyde Perspective formulas
2.2.3 Glyceraldehyde is conventionally used as the standard for defining d and l configurations: D-glyceraldehyde has the -OH group on the right, L-glyceraldehyde has the-OH group on the left.(fig. 2.2.4 For sugars with more than one asymmetric carbon atom, the D-and L- symbols refer to the absolute configuration of the asymmetric carbon farthest to the carbonyl group (e.g, in D-glucose, the -OH on C-5 has the same configuration as the asymmetric carbon in D glyceraldehyde, therefore, D-and L-glu ucoses are not enantiomers but stereoisomers!
2.2.3 Glyceraldehyde is conventionally used as the standard for defining D and L configurations: D-glyceraldehyde has the -OH group on the right, L-glyceraldehyde has the -OH group on the left. (fig.) 2.2.4 For sugars with more than one asymmetric carbon atom, the D- and L- symbols refer to the absolute configuration of the asymmetric carbon farthest to the carbonyl group (e.g., in D-glucose, the -OH on C-5 has the same configuration as the asymmetric carbon in Dglyceraldehyde, therefore, D- and L- glucoses are not enantiomers but stereoisomers!)