Adenosine-5'-d: rotational conformation of the 5'-carbinol group.

A synthesis of adenosine-5'-d (4), and its p.m.r. spectral characteristics, are described. The presence of deuterium in 4 gives rise to a 2:1 mixture of R and S configurations at C-5, thereby permitting specific assignments for the resonances of the residual 5'-protons. From the observed spin-spin coupling between the latter and H-4', an estimate has been made of the rotamer population of the exocyclic 5'-carbinol group. It is shown that the gauche-gauche rotamer is preponderant (approximately 70%) and the gauche-trans one of minor importance (approximately 20%) in aqueous solution, which contrasts markedly with the preference for the latter rotamer exhibited by adenosine in the solid state.