20. Carbohydrates

Draw a Haworth projection for α-D-altrose.

D-ribose is an aldopentose sugar that is found in the DNA. It commonly exists as a five-membered β anomer. Draw D‑ribose in its cyclic hemiacetal form.

In the monosaccharide hemiacetal shown below number all the carbon atoms, identify the anomeric carbon atom, and identify it as the α or ß anomer. <IMAGE>

The cyclic structure of d-idose, an aldohexose, is shown in the margin. Convert this to the straight-chain Fischer projection structure. <IMAGE>

Identify the following as diastereomers, enantiomers, and/or anomers. (a) ß-d-fructose and

ß-d-fructose (b) d-galactose and l-galactose (c) l-allose and d-glucose (both aldohexoses)

d-Talose, a constituent of certain antibiotics, has the open-chain structure shown next. Draw d-talose in its cyclic hemiacetal form. <IMAGE>