Oligonucleotides with alternating anionic and cationic phosphoramidate linkages: Synthesis and hybridization of stereo-uniform isomers

Tetrahedron Letters

Volumn 37, Issue 6, 1996, Pages 743-746

  Horn, Thomas ^a   Chaturvedi, Surendra ^b   Balasubramaniam, Tanjore N ^b   Letsinger, Robert L ^b  

^a NOVARTIS PHARMA AG   (Switzerland)

^b NORTHWESTERN UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

OLIGONUCLEOTIDE; PHOSPHORAMIDIC ACID DERIVATIVE;

ARTICLE; DRUG STRUCTURE; DRUG SYNTHESIS; HYBRIDIZATION; STEREOCHEMISTRY;

EID: 0030067307     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(95)02309-7     Document Type: Article

References (14)

1. Letsinger, R.L.; Singman, C.N.; Histand, G.; Salunkhe, M. J. Am. Chem. Soc. 1988, 110, 4470-4471.
2. Jung, P. M.; Histand, G.; Letsinger, R.L. Nucleosides & Nucleotides 1994, 13, 1597-1605.
3. Hashimoto, H.; Nelson, M.G.; Switzer, C. J. Am. Chem. Soc. 1993, 115, 7128-7134.
4. Fathi, R.; Huang, Q.; Coppola, G.; Delaney, W.; Teasdale, R.; Krieg, A.M.; Cook, A.F. Nucleic Acids Research 1994, 22, 5416-5424.
5. Reduced duplex stabilities have been observed for oligonucleotide phosphoramidate derivatives prepared without control of stereochemistry: Peyrottes, S.; Vasseur, J.J.; Imbach, J.L.; Rayner, B. Nucleosides & Nucleotides 1994, 13, 2135-2149; Froehler, B.C.; Ng, P.G.; Matteucci, M.D. Nucleic Acids Research 1988, 16, 4831-4839.
6. Reduced duplex stabilities have been observed for oligonucleotide phosphoramidate derivatives prepared without control of stereochemistry: Peyrottes, S.; Vasseur, J.J.; Imbach, J.L.; Rayner, B. Nucleosides & Nucleotides 1994, 13, 2135-2149; Froehler, B.C.; Ng, P.G.; Matteucci, M.D. Nucleic Acids Research 1988, 16, 4831-4839.
7. Miller, P.S.; Dreon, N.; Pulford, S.M.; McParland, K.B. J. Biol. Chem. 1980, 255, 9659-9665.
8. Ozaki, H.; Kitamura, M.; Yamana, K.; Murakami, A.; Shimidzu, T. Bull. Chem. Soc. Jpn. 1990, 63, 1929-1936.
9. Jäger, A.; Levy, M.J.; Hecht, S.M. Biochemistry 1988, 27, 7237-7246.
10. A clean separation was confirmed by thin layer chromatography of the products using silica gel plates with 8% methanol and 2% triethylamine in methylene chloride as eluent: Rf for 1a, 0.55; Rf for 2a, 0.38.
11. 2 showed peaks at 150.0 and 149.7 ppm (phosphoramidite groups) and a single peak at 10.4 ppm for the internucleoside phosphoramidate group. The ratio of the integrated areas for phosphoramidite/phosphoramidate was 1/1. Similarly, the "slow" stereoisomer exhibited phosphoramidite peaks at 150.0 and 149.7 ppm and a phosphoramidate peak at 10.6 ppm, and the ratio for the areas for phosphoramidite/phosphoramidate was 1:1. A mixture of the two dimer units showed the expected peaks, including well resolved peaks at 10.4 and 10.6 ppm for the two phosphoramidate stereoisomers. The presence of the latter two peaks demonstrates that one of the phosphoramidate stereoisomers can be readily detected in the presence of the other; therefore, appearance of a single peak in the spectrum of each dimer block indicates a high degree of uniformity in chirality at the phosphoramidate centers. All dimer blocks gave satisfactory FABS spectra.
12. 15, 27.35 min; 1, 20.15 min; 2, 20.15 min.
13. 2O showed the following bands, attributable to phosphoramidate groups: 1, +8.99 ppm; 2, +9.35 ppm; 1 + 2, 8.95 + 9.17 ppm. In addition, two bands attributable to phosphodiester groups were found in the region of -2.0 ppm (minor band) and -2.2 ppm (major band). The appearance of a distinctive signal for the phosphoramidate groups in 1 and a different signal for those in 2, together with resolution of the two bands in the mixture (1 + 2), shows that epimerization was minimal if it occurred at all.
14. 260 vs temperature.