Quanlai Song

A Short, Novel, and Cheaper Procedure for Oligonucleotide Synthesis Using Automated Solid Phase Synthesizer

Abstract Dimethylthiuram disulfide (DTD) has been developed as an efficient thiolation reagent during automated synthesis of oligonucleotides using phosphoramidite chemistry. Simultaneous thiolation and capping was accomplished by mixing DTD with capping solution B, which saved 20% of solvent consumption and compressed the four-step synthesis cycle to three. Large-scale (1 mmol) synthesis of phosphorothioate oligonucleotides has been demonstrated with excellent yield and purity.

KILO-SCALE SYNTHESIS PROCESS FOR 2′-O-(2-METHOXYETHYL)-PYRIMIDINE DERIVATIVES

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-methoxyethyl)-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.

UNEXPECTED RESULTS AND RECOURSE IN PROCESS OPTIMIZATION OF NUCLEOSIDE 3′-O-SUCCINATES

An improved and scalable protocol for the synthesis of 3′-O-succinates of nucleosides has been developed using succinic anhydride. As a result, formation of unwanted dimer has been completely eliminated and use of toxic and smelly reagents have been avoided during synthesis of nucleoside succinates. All succinates were isolated in pure state without silica gel column chromatography.