A process for the preparation of cladribine of API grade is provided by direct coupling of O-protected 2-deoxy-ribofuranose with silylated 2-chloroadenine followed by deprotection of the resultant protected nucleoside in a separate step and then a purification step. Following the coupling, the desired N-9-glycosylated β-anomer of the nucleoside is directly isolated as a solid from the coupling reaction mixture by filtration in relatively high purity and yield, and it does not require purification.
A method of making cladribine with an increased purity is provided by
a) dissolving crude cladribine in a protic solvent in the presence of a base to form a solution comprising dissolved crude cladribine;
b) maintaining the solution at an elevated temperature so that the solution is homogeneous until the amount of protected or partially protected nucleoside impurities in the solution is reduced to a pre-determined upper limit;
c) cooling the solution of step b) so that crystals of cladribine are formed and isolated.
A method of making cladribine with an increased purity comprising:
a) dissolving crude cladribine in a protic solvent in the presence of a base to form a solution comprising dissolved crude cladribine;
b) maintaining the solution at an elevated temperature so that the solution is homogeneous until the amount of protected or partially protected nucleoside impurities in the solution is reduced to a pre-determined upper limit; and
c) cooling the solution of step b) so that crystals of cladribine are formed and isolated.