NMR を利用した2',3'-O-アルキリデンウリジンの配座解析

抄録

Conformational analyses of 2′, 3′-O-methylene- [1], 2′, 3′-O-isopropylidene- [2], 2′, 3′-O-isobutylmethylene- [3], 2′, 3′-O-diheptylmethylene- [4], and 2′, 3′-O-diphenylmethyleneuridine [5] are examined by interpretation of proton magnetic resonance coupling constants and quantitative application of the nuclear overhauser effect (NOE). Dihedral anglesφ 1′, 2′ and φ 3′, 4′ in DMSO-d₆ at 22±1°C are slightly broadened in the order [1]>[2]>[3]≅[4]≅[5] because of the effect of steric barrier of alkylidene group. Under the same conditions, these compounds are found to exist primary in the syn-like conformation from NOE measurement. It is clarified that the population of the anti-conformation such as 2, 2′- and 2, 3′-anhydro nucleosides increases ([4]>[5]≅[3]>[2]>[1]) with the increase of bulkiness of the substituent of 2′, 3′-O-alkylidene group.