Two forms were found in the NMR spectra of N⁶-substituted 2-chloroadenosines. The proportion of the mini-form was 11–32% of the main form. It was characterized by a separate set of signals in NMR spectra. The team of scientists from IBCh RAS assumed that the mini-form arises due to an intramolecular hydrogen bond between the N⁶–CH proton of the substituent and the N7 atom of purine. The ¹⁵N-HMBC spectrum confirmed the presence of a hydrogen bond in the mini-form of the nucleoside and its absence in the main form. Compounds incapable of forming such a hydrogen bond were synthesized. In these compounds, either the N7 atom of the purine or the N⁶–CH proton of the substituent was absent. The mini-form was not found in the NMR spectra of these nucleosides, confirming the importance of the intramolecular hydrogen bond in its formation.