Transformation of 2,2'-anhydro-1-beta-D-arabinofuranosylcytosine induced by hydrogen peroxide.

2,2'-Anhydro-1-beta-D-arabinofuranosylcytosine (I) is a more potent and less toxic antineoplastic agent than is cytarabine (1-beta-D-arabinofuranosylcytosine) (II). The anhydronucleoside (I) was found to be readily transformed by hydrogen peroxide into 2,2'-anhydro-5-hydroxy-1-beta-D-arabinofuranosylcytosine (III) by treatment with 0.025 M hydrogen peroxide at a neutral and slightly basic pH range (pH 6-9) and at room temperature. It was converted into non-UV-absorbing substance(s) by hydrogen peroxide at an alkaline pH (pH 11). Since hydrogen peroxide is produced by redox reactions in all living cells, it may be responsible for the alteration of I. Such transformations by hydrogen peroxide were not observed with cytarabine.