R. Busson et al., Unexpected shift to a 4-imino tautomer upon N-4-acylation of 5-methylcytosin-1-yl nucleoside analogues., NUCLEOS NUC, 18(4-5), 1999, pp. 1079-1082
In contrast with the behaviour of 5-unsubstituted cytosine nucleoside analo
gues, 5-methylcytosine derivatives show upon N-4-benzoylation, commonly use
d as base protection in oligonucleotide synthesis, a tautomeric change of t
he base moiety from a 4-amino- into a 4-imino isomer. In the latter form, w
hich is easily diagnosticized by C-13 NMR and confirmed by X-ray data, the
compounds seem to be hydrolytically less stable.