Cyclic Structures of Monosaccharides Practice Problems

Consider the following cyclic hemiacetal structure of D-mannose (an aldohexose sugar molecule):

Draw its straight-chain Fischer projection.

Number the carbons and identify the anomeric carbon in the following monosaccharide. Identify whether it is the α or ß anomer.

Classify the pairs of compounds listed below as enantiomers, diastereomers, and/or anomers.

i. α-lactose and β-lactose

ii. D-idose and L-idose

iii. D-mannose and D-altrose

L-Rhamnose is a deoxy sugar that can be found in various plants. Compare the structure of L-rhamnose with the structure of α-L-mannose and answer the following question. Is 6-deoxy-L-mannose an appropriate name for L-rhamnose? Explain why or why not.

Draw the product formed when altrose reacts with ethanol in the presence of an acid. Determine whether these products are acetals or hemiacetals.

D-glucose is a monosaccharide found in many fruits. Draw D-glucose in its cyclic hemiacetal form. [Both α and β anomers]

Galactose is a monosaccharide sugar which can be found in milk. Given the open-chain form of D-galactose, draw its cyclic hemiacetal α and ß forms.

Talose is a monosaccharide that forms a six-membered cyclic hemiacetal, known as its pyranose form. Draw the α-anomer of D-talose in its pyranose form.