Patent ID: 7038039
Filing Date: 2006-05-02
Classification: C07H

Abstract:
1. A process for preparing a nucleoside represented by formula (8): wherein B is a base independently selected from the group consisting of pyrimidine, purine, azapurine and deazapurine optionally substituted by halogen, alkyl, haloalkyl, alkenyl, haloalkenyl, alkynyl, amino, alkylamino, hydroxy, hydroxyamino, aminoxy, alkoxy, mercapto, alkylmercapto, aryl, aryloxy or cyano; R R X represents halogen, alkoxy or alkylthio; W represents oxygen or sulfur; Z represents oxygen, sulfur or optionally substituted carbon; and m represents an integer of 1 to 3; n represents 0 or 1; p and q represents an integer of 0 to 4; and r represents 0 or 1; provided that p, q, r and n meet the conditions of p+r≦n+1 and q≦2×(n+1)−2×(p+r) when Z is oxygen or sulfur and of p+r≦n+2 and q≦2×(n+2)−2×(p+r) when Z is carbon; which comprises the steps of: (a) preparing a 1-phosphorylated saccharide compound monomer represented by formula (3): wherein R wherein where R to give α and β isomers of the 1-phosphorylated saccharide compound monomer; selectively crystallizing one of these isomers to displace the equilibrium between these anomers without the use of an enzymatic reaction; and then removing the protective group represented by R (b) conducting an exchange reaction of the phosphate group in the 1-phosphorylated saccharide compound monomer of formula (3) obtained in the step (a) with a base by the action of a nucleoside phosphorylase to obtain the a nucleoside represented by formula (8).