Nucleic Acids in Chemistry and Biology

their great metabolic stability to the phosphorylase enzymes, which cleaves the glycosylic bond of normal
nucleosides. The carbocyclic analogues of adenosine (aristeromycin) and neplanocin A (Figure 3.20) are
both naturally occurring and display anti-tumour and antibiotic activity respectively. Carbovir (Figure 3.20),
a carbocyclic 2,3-dideoxy-2,3-didehydro analogue of guanosine, is a potent inhibitor of HIV replication,
as indeed are several corresponding 2,3-dideoxy and 2,3-dideoxy-2,3-didehydro nucleoside analogues
of inosine, guanosine and adenosine.

Nucleosides and Nucleotides 89

O

HO

HO OH

N

NH

H

N O

BzO O

BzO OBz

NH 2

HN

NH

O

HO O

HO OH

O

MeO

SCN O

Me

N

NH

O

HO O

HO OH

S

TrO O

OO

CN

TrO O

OO

CN

NMe 2

TrO O

O O

N

CH 2 Ph

CO 2 Et

NH 2

HN

O

O

HO O

HO OH

O

pseudouridine oxazinomycin 9-deazainosine

Figure 3.18 Syntheses of N- and C-nucleosides by building the base onto the sugar

HN

NH

O

O

HO

HO OH

O

O

H

O

O O

O

NMe 2

O O

O

O

O

O

O O

HO O

OO

CO 2 Me

O

HO O

HO OH

NH

O

O

β-pseudouridine

(i)-(iv) (v)

(viii) (vi), (vii)

(ix),(x)

showdomycin

Figure 3.19 Synthesis of showdomycin and pseudouridine from furan. Reagents: (i) OsO 4 , H 2 O 2 ; (ii) acetone, H;
(iii) CF 3 CO 3 H; (iv) resolution; (v) dimethylformamide; (vi) urea; (vii) H 3 O; (viii) furan-1-carbaldehyde,
NaOMe; (ix) ozone; and (x) Ph 3 PCHCONH 2