A Chemo-Enzymatic Synthesis of β-d-Arabinofuranosyl Purine Nucleosides

Abstract

A chemo-enzymatic synthesis of 9-(β-d-arabinofuranosyl)-2-fluoroadenine (Fludarabine) and 9-(β-d-arabinofuranosyl)-2-amino-6-methoxypurine (Nelarabine) using α-d-arabinofuranose 1-phosphate as a universal substrate and recombinant E. coli purine nucleoside phosphorylase (PNP) as a biocatalyst is described. MacDonald's method was employed for the synthesis of α-d-arabinofuranose 1-phosphate, which was prepared as a mixture with β-d-arabinopyranose 1-phosphate, starting from peracyl derivatives of d-arabinose of different isomeric (anomeric) composition. It was found that the mixed phosphates can be successfully used in the reaction with purine base catalyzed by PNP pointing to the inertia of β-d-arabinopyranose 1-phosphate in regard to PNP. Reaction of 2-fluoroadenine and α-d-arabinofuranose 1-phosphate is shifted towards the formation of Fludarabine, whereas the reaction of 2-amino-6-methoxypurine reached equilibrium at a ca. equimolar ratio of the base and Nelarabine. Recombinant E. coli uridine phosphorylase catalyzed the synthesis of 1-(β-d-arabinofuranosyl)thymine (ara-T) from thymine and α-d-arabinofuranose 1-phosphate.