N.m.r. studies of the conformation of analogues of methyl β-lactoside in methyl sulfoxide- d6

Abstract

The 1H- and 13C-n.m.r. spectra of solutions of methyl β-lactoside ( 1), all of its monodeoxy derivatives ( 2, 3, 6–10), the 3- O-methyl derivative ( 4), and methyl 4- O-β- d-galactopyranosyl- d-xylopyranoside ( 5) in methyl sulfoxide- d 6 have been analysed. The n.O.e.'s and specific deshieldings indicate similar distributions of low-energy conformers, comparable to those in aqueous solution. The major conformer has torsion angles φ H and ψ H of 49° and 5°, respectively, with contributions of conformers with φ/ψ 24°/−59°, 22°/32°, and 6°/44°.