Aldoses Fischer projection formulas

The formation of a hemiacetal ring gives rise to a new chiral center in the aldoses, namely, at the C-1 atom. This leads to two C-1 epimers, termed anomers. When the hydroxyl group at C-1 (glycosidic hydroxyl) in the Fischer projection formula is located on the same side as the hemiacetal ring, the anomer is termed the a form in the opposite case it is the j3 form (Fig. 2-5). 

Terms in bold are defined glycoconjugate 238 monosaccharide 238 oligosaccharide 238 disaccharide 238 polysaccharide 238 aldose 239 ketose 239 Fischer projection formulas 240 epimers 240... 

The formula below is the Fischer projection for the acyclic form of D-glucose. The Fischer projections of the other aldoses (in the acyclic form) are given in Chart I (2-Carb-2.2)., ... 

Solutions of aldoses at equilibrium contain mixtures of at least two (a and 3) furanoses and two (a and 3) pyranoses. Typically, the two pyranose forms predominate at equilibrium. The anomeric carbon is chiral (C-1 of aldoses and C-2 of ketoses). In the D-series, if the OH on the anomeric carbon is to the right in a Fischer projection or below the plane of a Haworth perspective formula, the isomer is a and it is 3 if the OH is to the left or above. Conversely, in the L-series, the a anomer has the OH at carbon 1 to the left or... 

Figure 4.1 shows the formulas and names for D-aldoses using simplified Fischer projections. The occurrence of aldoses of importance in food is compiled in Table 4.1. Epimers are monosaccharides which differ in configuration at only one chiral C-atom. D-Glucose and D-mannose are 2-epimers. D-glucose and D-galactose are 4-epimers. 

---