Organic Chemistry of Drug Synthesis. Volume 7

HO

H O

O 117

C 2 H 5 O

H 3 C O

118

H 2 N

NH 2

S

119

+

SbCl 3

HO

NH

NH

H 3 C S

C 2 H 5 O

O

120

Half of the bases in RNA and DNA consist of pyrimidine nucleosides.
Analogues based on those nucleosides have, as result, been intensively
investigated as sources for both antitumor and antiviral compounds. Such
analogues, whether modified on the sugar portion or the base itself could
in theory act as false substrates for processes dependent on those nucleo-
tides at target cells, and lead to their demise. Replacement of one of the
hydrogen atoms in the sugar portion of cytidine by fluorine results in a
compound that has shown activity against the hepatitis B virus.

OCOCH 3

PhCO 2 OCOPh

PhCO (^2) O
Ph = C 6 H 5 121
OCOPh
PhCO 2 OH
PhCO O
OCOCH 3
PhCO 2
PhCO (^2) O
OSO
2
N
HBr 1. SO^2 Cl^2

2. Pyrrole
   122 123

OCOCH 3

PhCO 2

PhCO (^2) O
F
124
HBr
PhCO 2
PhCO (^2) O
N F Br
N
H 3 C
OSi(CH 3 ) 3
Si(CH 3 ) 3
125
PhCO 2
PhCO (^2) O
F
126
N
NH
O
O
H 3 C
127
HO
HO O
F
N
NH
O
O
H 3 C
NaOH
128
Bu 4 N+F-

2. COMPOUNDS WITH TWO HETEROATOMS 129