guanosine can be synthesized from a protected ribofuranosyl chloride and a
chloromercurieguanine.
O
OAcOAc
H
AcO
Cl
N
N
N
N
ClHg
O
NHAc
Ac
N
N
O
OAcOAc
AcO
N
N
O
NHAc
Ac
+
-HgCl 2
OH- H 2 O
Guanosine
Nucleosides can also be prepared through the formation of the heterocyclic
base on a protected ribosylamine derivative.
O
OAcOAc
AcO
NH 2
O
OAcOAc
AcO
N
N
O
H
O
O
N
H
O
OEt
EtO
+
(− 2 x EtOH)
OH- H 2 O
Uridine
2,3,5-Tri-O-acetyl-β-D-ribofuranosylamine
β-Ethoxy-N-ethoxycarbonylacrylamide
Phosphorylation of nucleosides produces corresponding nucleotides. Phosphorylating agents, e.g. dibenzylphosphochloridate, are used in this reaction. To carry out phosphorylation at C-5
0 , the other two hydroxyl
functionalities at C-2
0 and C-3
0 have to be protected, usually with an
isopropylidine group. At the final step, this protecting group can be removed
by mild acid-catalysed hydrolysis, and a hydrogenolysis cleaves the benzylphosphate bonds.
O
O
H
N
N
O
H
O
O O
Me Me
O P
O
O
Cl
Ph
Ph
O P
O
O
O N
N
O
H
O
O O
Me Me
Ph
Ph
H 2 , Pd
O
H P
O
O
H
O N
N
O
H
O
OH OH
Dibenzylphosphochloridate
+
Isopyrilidine
protecting group
H 2 O, H +
Uridine 5'-phosphate
A nucleotide
172
CH4 ORGANIC FUNCTIONAL GROUPS