Chapter 25, Problem 2PP

Interpretation Introduction

Interpretation:

The reason for the susceptibility of nucleosides to acidic hydrolysis and the mechanism of this hydrolysis is to be explained.

Concept introduction:

舧 Electrophiles are electron-deficient species, which has positive or partially positive charge. Lewis acids are electrophiles, which accept electron pair.

舧 Nucleophiles are electron-rich species, which has negative or partially negative charge. Lewis bases are nucleophiles, which donate electron pair.

舧 A nucleoside consists of a nucleobase (also termed as nitrogenous base) and a five-carbon sugar (either ribose or deoxyribose).

舧 A nucleotide consists of a nucleobase (also termed as nitrogenous base), a five-carbon sugar (either ribose or deoxyribose) and one or more phosphate groups.

舧 In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or N1 of a pyrimidine.

舧 Examples of nucleosides include cytidine, uridine, adenosine, guanosine and thymidine.

舧 Sugar (ribose/deoxyribose) and nitrogenous bases are linked through N-glycosidic bonds.

舧 These glycosidic bonds are formed by condensation reaction of first carbon of sugar molecule with the nitrogen atom $(\text{N1 of pyrimidines and N9 of purines)}$ of the nitrogenous base.

舧 This particular glycosidic bond is stable in basic solutions, but readily hydrolyzes in the presence of acids.