Nucleic Acids in Chemistry and Biology

Nucleosides and Nucleotides 97

AcO O

AcO

N

NH

O

O

X

AcO O

AcO

N

N

N

O

X

N

N O

HO

HO

N

N

NH 2

O

X

HO O

HO

N

N

Y

O

X

X = H , F, NHCOCF 3 , OAc

X = H , F, NH 2 , OH

(i)

X = H, Y = OMe, NHOH, NHNH 2

(ii)

(iii), (iv) or (v)

Figure 3.31 Conversion of uridine and 2-modified uridines into 2-modified cytidines and C-4 modified
2 -deoxyribopyrimidine nucleosides. Reagents: (i) POCl 3 , triazole, Et 3 N, CH 3 CN; (ii) NH 3 in dioxan, heat;
(iii) DBU in MeOH then NH 4 OH; (iv) NH 2 OH.HCl in pyridine then NH 4 OH; and (v) NH 2 NH 2 in EtOH, heat

RO O

RO

N

NH

N

N

O

NHR

O

OSO

RO O

RO

N

N

N

N

NHR

R'

HO O

HO

N

N

N

N

NH 2

RO O

RO

N

N

N

N

NHR

NHNH 2

OMe

HO O

HO

N

N

N

N

NH 2

NMe 3

RO O

RO

N

N

N

N

NHR

HO O

HO

N

N

N

N

NH 2

(i) (v), (iv)

(ii)

R = Bz or TBDMS (on 3' and 5', R = H on base)

R' = 2,4,6-i-PrC 6 H 2 or 4 -MeC 6 H 4 for (i) & (v)

(iii),(iv)

(vii),(iv)

(vi)

Figure 3.32 Syntheses of some 6-substituted purine nucleosides via O^6 -sulfonate esters. Reagents: (i) arylsulfonyl
chloride, 4-dimethylaminopyridine, Et 3 N, CH 2 Cl 2 ; (ii) NH 2 NH 2 in THF; (iii) Ag 2 O in THF/H 2 O; (iv)
Deprotection; NaOMe in MeOH for RBz, TBAF in THF for RTBDMS; (v) H 2 C^ CHSnBu 3 ,
Pd(PPh 3 ) 4 , LiCl, dioxan; (vi)trimethylamine; and (vii) MeOH, DBU

HO O

HO

N

NH

N

N

O

NH 2

N

CF 3 COO O

CF 3 COO

N

N

N

N

NHCOCF 3

S

HO O

HO

N

NH

N

N

NH 2

(i) (ii), (iii)

Figure 3.33 One-pot conversion of 2-deoxyguanosine into 6-thio-2-deoxyguanosine. Reagents: (i) (CF 3 CO) 2 CO
in pyridine; (ii) NaSH in DMF; and (iii) dilute NH 4 OH