The design and synthesis of potential antitumor
antimetabolites 2'-deoxy-2'-(hydroxylamino)uridine (15), -
cytidine (19, 2'-DHAC), and -
adenosine (35), their regioisomers, 3'-deoxy-3'-(hydroxylamino)uridine (40) and -
cytidine (45, 3'-DHAC), and their 2'-deoxy analogues, 2', 3'-dideoxy-3'-(hydroxylamino)uridine (49) and -
cytidine (52, 3'-dDHAC), are described. We measured the pKa values of the hydroxylamino group in 15 and 40 using 13C NMR spectroscopy as a function of pH to be 2.9 and 3.4, respectively. We also found that these
nucleosides gradually decomposed in neutral
solution but not in acidic
solution. This decomposition may be related to the generation of aminoxy radicals at the
sugar moiety. The in vitro cytotoxicity of these
nucleosides was evaluated using L1210 and KB cells.
2'-DHAC (19) inhibited the growth of L1210 and KB cells, with IC50 values of 1.58 and 1.99 microM, respectively.
3'-DHAC (45) and 3'-dDHAC (52) were also cytotoxic against L1210 cells, with IC50 values of 4.03 and 1.84 microM, respectively, but not against KB cells. The cytotoxicity of
2'-DHAC (19) and
3'-DHAC (45) against L1210 cells in vitro was reversed by the addition of
cytidine, while that of 3'-dDHAC (52) was reversed by 2'-deoxycytidine.
2'-DHAC (19) and 3'-dDHAC (52) mainly inhibited
DNA synthesis in L1210 cells, while
3'-DHAC (45) inhibited
RNA synthesis. We also evaluated the antitumor activities of
2'-DHAC (19) and
3'-DHAC (45) against murine Meth-A
fibrosarcoma cells in vivo.
2'-DHAC (19) was more active than
3'-DHAC (45) when administered intravenously on days 1-10 consecutively
at 10 mg/kg/day.
2'-DHAC (19) inhibited
tumor growth at a rate of 66.9%.