Crystal structures of (+/-)-(1SR,5SR,6SR,7SR,10SR,11SR,13RS,14SR)-13-hydroxy-7-methoxymethoxy-11,15,18,18-tetramethyl-3-oxo-2,4-dioxatetracyclo[12.3.1.0 (1,5).0(6,11)]octadec-15-en-10-yl benzoate, its 13-epimer and 13-one derivative

The title compounds, C29H38O8 center dot 0.25C(5)H(12), (A), C29H38O8, (B), and C29H36O8, (C), are tetracyclic benzoates possessing a taxane skeleton with a fused dioxolane ring as the core structure. In the asymmetric unit of (A), there are two independent benzoate molecules (A and A') and a half molecule of solvent pentane disordered about an inversion center. The molecular conformations of (A), (B) and (C) are similar except for the flexible methoxymethoxy group. The cyclohexane, cyclohexene and central cyclooctane rings adopt chair, half-chair and chair-chair (extended crown) forms, respectively. The dioxolane rings are essentially planar, while the dioxolane ring of A' is slightly twisted from the mean plane. In the crystal of (A), intermolecular O-H center dot center dot center dot O, C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions link the independent benzoates alternately, forming a chain structure. In the crystals of (B) and (C), molecules are linked through O-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions, and C-H center dot center dot center dot O hydrogen bonds, respectively, into similar chains. Further, weak intermolecular C-H center dot center dot center dot O interactions connect the chains into a three-dimensional network in (A) and a sheet in (B), whereas no other interactions are observed for (C).