Crystal structure and absolute configuration of methyl 3,4-di-O-acetyl-6-deoxy-6-iodo-2-O-p-tolylsulphonyl-α-D-mannopyranoside

Abstract

The title compound (7) was isolated as a minor product of successive tosylation, acetylation and iodide displacement of methyl α-D-mannopyranoside (1). Crystals of the title compound are orthorhombic, space group P2₁2₁2₁, a= 9.293(2), b= 14.220(6). c= 16.969(6)ÅZ= 4. The structure was solved from diffractometer data by heavy-atom techniques, and refined by block-diagonal least-squares methods to R 0.052 for 1 802 independent reflections. The results supply the constitution and absolute configuration (8). The conformation of the pyranoside ring is ⁴C₁(C1) in the solid state and ¹H n.m.r. studies showed this to be the predominant conformation in solution also.