Kilo-scale synthesis process for 2'-O-(2-methoxyethyl)-pyrimidine derivatives.

Bruce S Ross, Quanlai Song, Mingming Han

Index: Nucleosides Nucleotides Nucleic Acids 24(5-7) , 815-8, (2005)

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Abstract

We describe an improved process to produce 2'-O-(2-methoxyethyl)-pyrimidines. Starting with commercially available O-2,2'-anhydro-5-methyluridine and tris-(2-methoxyethyl)borate, we modified the ring-opening reaction conditions and changed to a continuous extraction purification method to give 2'-O-(2-methaxyethyl)-5-methyluridine. The dimethoxytritylation 5'/3' ratios and yield were improved by the use of 2,6-lutidine as the base. Conditions to convert to the 5'-methylcytidine analog and its isolation by crystallization were optimized. Final benzoylation was improved by developing a method to selectively hydrolyze benzoyl ester impurities.