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29Si NMR spectra of trimethylsilyl and tert-butyldimethylsilyl derivatives of purines and pyrimidines

✍ Scribed by Jan Schraml; Magdalena Kvíčalová; Vratislav Blechta; Roman Řeřicha; Jef Rozenski; Piet Herdewijn

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
290 KB
Volume
36
Category
Article
ISSN
0749-1581

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✦ Synopsis

Trimethylsilyl and tert-butyldimethylsilyl derivatives of naturally occurring purines and pyrimidines and also other closely related model compounds were prepared and their 29Si NMR spectra measured. Only the chemical shifts of the SiÈNHÈ moiety could be assigned experimentally (i.e. exactly) ; the chemical shifts of SiÈOÈ and SiÈNÈ fragments could be assigned only on the basis of chemical shift correlations. The SiÈNÈ lines are surprisingly narrow in all derivatives of nucleic bases studied. The lines are narrow because of the "self decouplingÏ of fast relaxing 14N nuclei. The values of 29Si, 15N coupling constants could not be reliably determined (by the HEEDÈINEPT method), nor could the SiÈN lines be completely assigned in these compounds. Measurement of 29Si NMR spectra is shown to be a sensitive and fast method for checking completeness of silylation of nucleobases or their analogues. Assignment difficulties limit other applications.

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