Conformational Analyses of 2′, 3′-0-Alkylideneuridines by the use of Nuclear Magnetic Resonance

Abstract

Conformational analyses of 2′, 3′-O-methylene- -isopropylidene- isobutylmethylene- 2′, 3′-O-diheptylmethylene-, and 2′, 3′-0-diphenylmethyleneuri-dine are examined by interpretation of proton magnetic resonance coupling constants and quantitative application of the nuclear overhauser effect (NOE). Dihedral angles and in DMSO- at 22±1°C are slightly broadened in the order = mbecause 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-qonformation such as 2,2′- and 2,3′-anhydro nucleosides increases with the increase of bulkiness of the substituent of 2′, 3′-O-alkylidene group. © 1988, The Chemical Society of Japan. All rights reserved.