Question

2. Draw the structural formula for a- D-glucosyl-(1->6)-D-mannosamine, and circle the part of this structure that makes the compound a reducing sugar. (4 pts.)

Answer 1

Answer -

1. $\alpha$ - D - glucosyl- (1$\rightarrow$6) - D - mannosamine is disaccharide in which glucose and mannosamine are linked with each other by $\alpha$ (1$\rightarrow$6) glycosidic bond. In bond formation C1 of glucose and C6 of mannosamine are involved.

2. The C1 of aldoses has free aldehydic group with ability of reduction and when glycosidic bonds are formed between sugars C1 is involved in bond formation. If C1 is involved in glycosidic bond formation that sugar can not form linear structure and has lost ability of reduction.

3. In this disaccharide glucose has no free anomeric carbon so that glucose is non reducing. But anomeric carbon of mannosamine is free so that it is capable of reduction.

4. So that in this disaccharide anomeric C1 of mannosamine is reducing carbon that makes compound reducing sugar.

CH₂OH 은 OLI 공 н L-D-glucose оң (216) glycosidic bond H o o H Cue anomerie e free anomeric & 20H carbon showing free aldehyde group which is reducing part of 4 H sugar. L-D-Mannosamine C-D-glucosyl-(16)-D-mannosamine