Chapter 25, Problem 5PP

Interpretation Introduction

Interpretation:

The structure of cordycepin and the mechanism of conversion of its thioethyl derivative to $2\text{'-deoxyadenosine}$ are to be proposed.

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 Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon or a functional group is substituted by any other functional group is called substitution reaction.

舧 Elimination reaction: A reaction in which two substituent groups are detached and a double bond is formed is called elimination reaction.

舧 Addition reaction: It is the reaction in which unsaturated bonds are converted to saturated molecules by the addition of molecules.

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.

舧 Cordycepin is a nucleoside containing $3\text{'}$ -deoxyribose sugar bound to adenine. It is an isomer to adenine nucleoside containing $2\text{'}$ -deoxyribose, which is a naturally occurring nucleoside in DNA. The high degree of structural similarity between cordycepin and adenosine makes cordycepin a potential nucleoside analogue.

舧 Reductive desulfurization occurs in the presence of Raney Nickel. This results in the elimination of sulfur followed by the reduction