How do the aglycones drive the pseudorotational equilibrium of the pentofuranose moiety in C-nucleosides?

Abstract

The nature of the π-charge delocalisation in the ‘5,6-en-4-one’ system in the aglycone of C-nucleosides 1–4 promotes the interactions with O4′ and/or O2′ lone-pairs or H-bonding between C4-carbonyl and 2′-OH placing the aglycone preferentially either in pseudoequatorial or pseudoaxial orientation, which energetically dictates the drive of the North ⇄ South sugar pseudorotational equilibrium.