Spectroscopic evidence for a radical cation as intermediate in a model reaction of the 4′-DNA radical strand cleavage

Journal of the American Chemical Society

Volumn 119, Issue 37, 1997, Pages 8740-8741

  Gugger, Andreas ^a   Batra, Rohit ^a   Rzadek, Piotr ^b   Rist, Günther ^b   Giese, Bernd ^a  

^a UNIVERSITY OF BASEL   (Switzerland)

^b NOVARTIS PHARMA AG   (Switzerland)

Author keywords

[No Author keywords available]

Indexed keywords

RADICAL;

ARTICLE; CHEMICAL ANALYSIS; DNA CLEAVAGE; DNA STRAND BREAKAGE; POLARIZATION; REACTION ANALYSIS; SPECTROSCOPY; STEREOCHEMISTRY;

EID: 0030929539     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja971677y     Document Type: Article

References (28)

1. (a) Zipse, H. Angeu: Chem., Int. Ed. Engl. 1994, 33, 1985.
2. (b) Curran, D. P. Chemtracts: Org. Chem. 1995, 8, 62.
3. (a) Giese, B.; Dussy, A.; Elie, C.; Erdmann, P.; Schwitter, U. Angew. Chem.. Int. Ed. Engl. 1994, 33, 1861.
4. (b) Giese, B.; Beyrich-Graf, X.; Erdmann, P.; Petretta, M.; Schwitter, U. Chem. Biol. 1995, 2, 367.
5. For pioneering work in this area, see: Behrens, G.; Koltzenburg, G.; Schulte-Frohlinde, D. Z Naturforsch. C 1982, 37, 1205.
6. Caramella, P.; Cellerino, G.; Corsico Coda, A.; Gamba Invernizzi, A.; Grünanger, P.; Houk, K. N.; Marinone Albini, F. J. Org. Chem. 1976, 41, 3349.
7. Curran, D. P. J. Am. Chem. Soc. 1983, 705, 5826.
8. The new compounds were fully characterized by spectroscopic techniques and elemental analysis (data given in the Supporting Information). Compounds 6a and 6b (assigned by NOE experiments and cis-γ-effect) were separated by flash chromatography on silica gel with diethyl ether/ ethyl acetate (100:0 to 80:20) as eluents.
9. For the multiple laser pulse experiment, the observing radiofrequency pulse followed a saturation pulse sequence and 10 laser pulses with delay times of 5 ms.
10. 4 (0.6 mL), degassed for 10 min with Nz, and sealed in a NMR quartz tube. The solution was irradiated at 25 °C with an excimer laser (Questek) coupled with a dye laser (Lambda Physik) at λ = 342 nm (11 mJ/pulse) in the magnetic field of a Bruker AM200 NMR spectrometer (200 MHz wide bore).
11. The experiment was carried out as in ref 8 using a Nd-Yag laser (Continuum, Surlite II) at λ = 355 nm (100 mj/pulse).
12. Goetz, M. Concepts Magn. Reson. 1995, 7, 69-86.
13. Adrian, F. J. J. Chem. Phys. 1970, 53, 3374.
14. Kaptein, R.; Oosterhoff, L.; Chem. Phys. Lett. 1969, 4, 195, 214.
15. Closs, G. L. J. Am. Chem. Soc. 1969, 91, 4552.
16. Fischer, H. Z. Naturforsch. A 1970, 25, 1957.
17. Kaptein, R. J./1m. Chem. Soc. 1972, 94, 6251.
18. Kaptein, R. J. Chem. Soc., Chem. Commun. 1971, 732.
19. Batra, R.; Giese, B.; Spichty, M.; Gescheidt, G.; Houk, K. N. J. Phys. Chem. 1996, 100, 18371.
20. Turro, N. J. Modem Molecular Photochemistry; University Science Books: Sausalito, CA, 1991; p 531.
21. The following g-values were used: g(7) ≈ 2.0006; g(9) ≈ 2.0030 (see (a) Grossi, L.; Placucci, G. J. Chem. Soc., Chem. Commun. 1985, 943.
22. (b) Madelung, O.; Fischer, H. Landolt-Bomstein New Series, II/17h, refs 80-84).
23. 1 Values were measured by the inversion recovery method on a Varian Gemini 300 (300 MHz) NMR spectrometer.
24. Borer, A.; Kirchmayer, R.; Rist, G. Helv. Chim. Acta 1978, 61, 305.
25. The ionization potentials were calculated with the compound method CBS-Q: Ochterski, J. W.; Peterson, G. A.; Montgomery, J. A. J. Chem. Phys. 1996,104,2598. The calculated ionization potential of 8.0 eV for 11 is in agreement with its photoelectron spectrum.
26. For the analysis of the products, phenyl ketone 6a (35 mg) was dissolved in MeOH (1 mL), degassed for 10 min with Ni, and sealed in a NMR quartz tube. The solution was irradiated at 25 °C with a Nd-Yag laser (Surelite) at 355 nm (39 mJ/pulse) for 30 min. The products were identified and quantified by GC using undecane as an internal standard and synthesized or commercially available reference substances.
27. -1 (see Burchill, C. E.; Ginns, I. S. Can. J. Chem. 1970,48, 1232, 2628). Presumably, after this slow reaction step, the polarizations are diminished to such an extent that they are no longer observable for acetal 12.
28. -1 at 25 °C in MeOH (unpublished results of S. Peukert and M. Obkircher, Basel).