Nucleic Acids in Chemistry and Biology

Nucleosides and Nucleotides 91

N

N N

N

X

Y

N

N

NH 2

O

NH

N

O

O

Z

NH

N N

N

O

NH 2

HO OAc MeOCO 2 OCO 2 Me MeOCO 2 B

(+)

10 steps (^) (i)
B =
X=Cl,Y=NH 2
X=NH 2 , Y=Cl
X=Cl, Y=H
Z=H,Me,F
60-87%
Figure 3.21 Syntheses of carbocyclic nucleosides using Pd(0)-catalysed allylic coupling. Reagents: (i) Base (BH),
Pd(PPh 3 ) 4 , DMF
O O
HO H
H
HO N
N
NHBz
O
AcO
AcO
HO
N
N
N
N
NH 2
HO N
N
NHBz
O
HO OH
HO
N
N
N
N
NH 2
HO OH
HO
N
N
N
N
NH 2
HO OH
HO N
N
NHBz
O
(i) HO OH
85%
43%
(ii)
(ii)
(iii)
(iii)
(13% N-7 isomer)

• 
  


• 
  

  Figure 3.22 Syntheses of carbocyclic nucleosides using Pd(0)-catalysed allylic coupling. Reagents: (i) OCH.CO 2 H;
  (ii) diastereomeric resolution and deprotection; (iii) Cs salt of base, Pd(PPh 3 ) 4 , 55°C, DMF, then
  NH 3 /MeOH; and (iv) OsO 4 , trimethylamine-N-oxide
  HO
  HO OH
  N
  N
  N
  N
  BnO NH^2
  O O
  OH
  BnO
  O O
  N
  N
  N
  N
  Cl
  neplanocin A
  70%
  (i)
  Figure 3.23 Use of the Mitsunobu reaction in the synthesis of neplanocin A. Reagents: (i) Ph 3 P,
  EtO 2 CN^ NCO 2 Et, THF, 6-chloropurine