The absolute stereochemistry proposed for the enantiomers of the carbonucleosides cis- and trans-6-chloro-9-[2-(hydroxymethyl)cyclopentyl]-9H-purine, 1 and 2, respectively, should be questioned because of the erroneous use of the auxiliary reagent methoxyphenylacetic acid (MPA, 3), and the low quality of the NMR data used for the assignment. For a rigorous application of the NMR method to those primary alcohols, 9-anthrylmethoxyacetic acid (9-AMA, 4) should be used as the auxiliary reagent and structural calculations should be carried out to validate the NMR model.