Nucleic Acids Research, 1983, Vol. 11, No. 15 5189-5204
© 1983
CHEMISTRY |
Use of methylphosphonic dichloride for the synthesis of oligonucleoside methylphosphonates
Division of Biophysics, School of Hygiene and Public Health, Johns Hopkins University Baltimore, MD 21205, USA
Received June 15, 1983. Accepted July 13, 1983.
Methylphosphonic dichloride was used to prepare protected deoxyribo-nucleoside 3'-methylphosphonate ß-cyanoethyl esters, d-[(MeO)2Tr]NpCNEt, and protected oligonucleoside methylphosphonates in solution. Reaction of d-[(MeO)2Tr]N with methyl phosphonic dichloride gives d-[(MeO)2Tr]NpCl. The phosphonylation and subsequent esterification or condensation reactions are each complete within 60 min. The products are readily purified by "flash chromatography" on silica gel columns. d-[(MeO)2Tr]NpCl, or Its tetrazole derivative, d-[(MeO)2Tr]Nptet, were tested as intermediates for the synthesis of oligothymidine methylphosphonates on a silica gel polymer support. The average yield per coupling step was 76% and did not Increase with addition of more d-[(MeO)2Tr]TpCl . The formation of (5'-5') linked thymidine dimers Indicated that the thymidine monomers are clustered closely together on the support. When N is ibuG, the yield for the coupling step on the support is very low. This may be due to steric hindrance of the 3'-phosphonate group by the N-2 isobutryl protecting group.