Solution stability and degradation pathway of deoxyribonucleoside phosphoramidites in acetonitrile.
The impuritiy profiles of acetonitrile solutions of the four standard O-cyanoethyl-N,N-diisopropyl-phosphoramidites of 5'-O-dimethoxytrityl (DMT) protected deoxyribonucleosides (dG(ib), dA(bz), dC(bz), T) were analyzed by HPLC-MS. The solution stability of the phosphoramidites decreases in the order T, dC>dA>dG. After five weeks storage under inert gas atmosphere the amidite purity was reduced by 2% (T, dC), 6% (dA), and 39% (dG), respectively. The main degradation pathways involve hydrolysis, elimination of acrylonitrile and autocatalytic acrylonitrile-induced formation of cyanoethyl phosphonoamidates. Consequently, the rate of degradation is reduced by reducing the water concentration in solution with molecular sieves and by lowering the amidite concentration. Acid-catalyzed hydrolysis could also be reduced by addition of small amounts of base.
Drug Substance Manufacturing, Isis Pharmaceuticals, Inc., Carlsbad, California 92008, USA. akrotz@isisph.com
Achim H
AH
Krotz
Claus
C
Rentel
Dennis
D
Gorman
Phil
P
Olsen
Hans J
HJ
Gaus
James V
JV
McArdle
Anthony N
AN
Scozzari
D000097:Acetonitriles / Q000737:chemistry*; D003853:Deoxyribonucleosides / Q000737:chemistry* / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000737:chemistry*; D012996:Solutions
D000097:Acetonitriles; D003853:Deoxyribonucleosides; D009943:Organophosphorus Compounds; D012996:Solutions; C434331:phosphoramidite; C032159:acetonitrile