Crystal structures of (±)-(1 SR,5 SR,6 SR,7 SR,10 SR,11 SR,13 RS,14 SR,15 SR,16 RS)-13-acet­oxy-16-benzyloxy-15-hy­droxy-7-meth­oxy­meth­oxy-3-oxo-11,15,18,18-tetra­methyl-2,4-dioxa­tetra­cyclo[12.3.1.0 ^1,5.0 ^6,11]octa­decan-10-yl benzoate and its 13-epimer

Abstract

The crystal structures of a fused tetra­cyclic benzoate and its epimer obtained in synthetic study of Paclitaxel are described. The corresponding ring conformations in both tetra­cycles are similar; however, one epimer shows two orientational disorders and while none occurs for the other. In each crystal, pairs of inter­molecular O—H⋯O hydrogen bonds connect the mol­ecules into inversion dimers. The dimers are further linked by weak inter­molecular C—H⋯O and/or C—H⋯π inter­actions.

Abstract

The title compounds, C ₃₈H ₄₈O ₁₁ ( A and B), are tetra­cyclic benzoates composed of a taxane ring with a fused dioxolane ring as the core skeleton. In compound A, the five-membered dioxolane ring is essentially planar while the two cyclo­hexane rings and the cyclo­octane ring adopt chair and chair–chair forms, respectively, and there are three intra­molecular H⋯H short contacts. The corresponding ring conformations in B are similar; however, one intra­molecular C—H⋯O inter­action and two H⋯H short contacts are observed, and the benzoyl and meth­oxy­methyl groups show orientational disorder. In the crystal of A, a pair of inter­molecular O—H⋯O hydrogen bonds link two mol­ecules into an inversion dimer, and weak inter­molecular C—H⋯O inter­actions connect the dimers, forming a three-dimensional network. In the crystal of B, an inversion dimer is similarly generated by a pair of inter­molecular O—H⋯O hydrogen bonds, and weak inter­molecular C—H⋯O and C—H⋯π inter­actions connect the dimers into a three-dimensional architecture.