Stereospecific assignment of H5′ and H5" in a (5′R)-/(5′S)-deuterium-labeled DNA decamer for 3JHH determination and unambiguous NOE assignments

The stereoselective deuterium labeling at the 5' methylene protons of the ribose ring recently developed by Kawashima et al. [1995, Tetrahedron Lett., 36, 6699-6700] enabled the assignment of pro-R and pro-S protons at the 5' position. The deuterium-labeled nucleotides, [(5'S)-H-2]- and [(5'R)-H-2]-diastereomers, in an approximate ratio of 2:1, were incorporated in the decamer 5'-d(GCATTAATGC)-3', Thus, both pro-R and pro-S methylene proton signals without geminal coupling appeared in the NOESY and DQF-COSY spectra. Complete stereospecific assignments and simplified spin systems enabled the determination of 15 (3)J coupling constants between H4' and H5'/H5 ", and the unambiguous assignment of 135 NOESY cross peaks originating from H4'/H5'/H5 " resonances.