Question

Draw a structural formula for a nucleoside composed of the following. (a) \(\alpha\)-D-Ribose and adenine (b) \(\beta\)-2-Deoxy-D-ribose and cytosine

Short answer

Question: Draw the structural formulas for (a) a nucleoside made from α-D-Ribose and adenine, and (b) a nucleoside made from β-2-Deoxy-D-ribose and cytosine. Answer: (a) To create a nucleoside from α-D-Ribose and adenine, connect the anomeric carbon (C1) on α-D-Ribose to the nitrogen at position 9 of Adenine through a glycosidic bond. (b) For a nucleoside made from β-2-Deoxy-D-ribose and cytosine, connect the anomeric carbon (C1) on β-2-Deoxy-D-ribose to the nitrogen at position 1 of Cytosine through a glycosidic bond.

Step-by-step solution

Draw the structure of α-D-Ribose

To draw α-D-Ribose, we need to start with a pentose sugar ring with an anomeric carbon (C1) having the -OH group downward. The other hydroxyl (-OH) groups and hydrogen (H) atoms must be in the correct positions: on C2 and C3, the -OH groups should be upward, while on C4 it should be downward. Attach a CH2OH group to C5 towards the upward.

Draw the structure of Adenine

Adenine is a purine, consisting of a six-membered ring connected to a five-membered ring. The nitrogen atoms are at positions 1, 3, 7, and 9, with double bonds between N1 and C6, C5 and C4, and N7 and C8. There is a double bond between N7 and C8, and an amino group (NH2) is attached to C6.

Connect α-D-Ribose and Adenine

A nucleoside is formed when the anomeric carbon (C1) on α-D-Ribose is connected to the nitrogen at position 9 of Adenine through a glycosidic bond. This will create the structural formula for the nucleoside composed of α-D-Ribose and Adenine.

Draw the structure of β-2-Deoxy-D-ribose

In order to draw β-2-Deoxy-D-ribose, start with a pentose sugar ring with the anomeric carbon (C1) having the -OH group upward. The other hydroxyl (-OH) groups and hydrogen (H) atoms must be in the correct positions: on C2, replace the -OH group with just an H atom, while on C3 the -OH group should be upward. On C4, the -OH group should be downward. Attach a CH2OH group to C5, also towards the upward direction.

Draw the structure of Cytosine

Cytosine is a pyrimidine, consisting of a six-membered ring with nitrogen atoms at positions 1 and 3. There is an amino group (NH2) attached to C4, and a double bond between C2 and an oxygen atom, which is attached as a carbonyl group to C2.

Connect β-2-Deoxy-D-ribose and Cytosine

A nucleoside is formed when the anomeric carbon (C1) on β-2-Deoxy-D-ribose is connected to the nitrogen at position 1 of Cytosine through a glycosidic bond. This will create the structural formula for the nucleoside composed of β-2-Deoxy-D-ribose and Cytosine.