Crystal structures of (±)-(1<i>SR</i>,5<i>SR</i>,6<i>SR</i>,7<i>SR</i>,10<i>SR</i>,11<i>SR</i>,13<i>RS</i>,14<i>SR</i>,15<i>SR</i>,16<i>RS</i>)-13-acetoxy-16-benzyloxy-15-hydroxy-7-methoxymethoxy-3-oxo-11,15,18,18-tetramethyl-2,4-dioxatetracyclo[12.3

The title compounds, C₃₈H₄₈O₁₁ (<b>A</b> and <b>B</b>), are tetra-cyclic benzoates composed of a taxane ring with a fused dioxolane ring as the core skeleton. In compound <b>A</b>, the five-membered dioxolane ring is essentially planar while the two cyclo-hexane rings and the cyclo-octane ring adopt chair and chair-chair forms, respectively, and there are three intra-molecular H⋯H short contacts. The corresponding ring conformations in <b>B</b> are similar; however, one intra-molecular C-H⋯O inter-action and two H⋯H short contacts are observed, and the benzoyl and meth-oxy-methyl groups show orientational disorder. In the crystal of <b>A</b>, a pair of inter-molecular O-H⋯O hydrogen bonds link two mol-ecules into an inversion dimer, and weak inter-molecular C-H⋯O inter-actions connect the dimers, forming a three-dimensional network. In the crystal of <b>B</b>, an inversion dimer is similarly generated by a pair of inter-molecular O-H⋯O hydrogen bonds, and weak inter-molecular C-H⋯O and C-H⋯π inter-actions connect the dimers into a three-dimensional architecture.