Crystal structures of (±)-(1SR,5SR,6SR,7SR,10SR,11SR,13RS,14SR)-13-hy-droxy-7-meth-oxy-meth-oxy-11,15,18,18-tetra-methyl-3-oxo-2,4-dioxa-tetra-cyclo-[12.3.1.0(1,5).0(6,11)]octa-dec-15-en-10-yl benzoate, its 13-epimer and 13-one derivative

Crystal structures of (±)-(1SR,5SR,6SR,7SR,10SR,11SR,13RS,14SR,15SR,16RS)-13-acet-oxy-16-benzyloxy-15-hy-droxy-7-meth-oxy-meth-oxy-3-oxo-11,15,18,18-tetra-methyl-2,4-dioxa-tetra-cyclo[12.3.1.01,5.06,11]octa-decan-10-yl benzoate and its 13-epimer

The title compounds, C38H48O11 (A and B), are tetra-cyclic 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 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 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 A, 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, 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.

Crystal structure of (+)-(1S,5S,6S,7S,10S,11S,16S)-16-hy-droxy-7-(meth-oxy-meth-oxy)-11,15,18,18-tetra-methyl-3,13-dioxo-2,4-dioxa-tetra-cyclo[12.3.1.01,5.06,11]octa-dec-14-en-10-yl benzoate

In the fused tetra-cyclic system of the title compound, C29H36O9, the five-membered dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of the other three atoms by -0.252 (6) and 0.340 (6) Å. The cyclo-hexane, cyclo-hexene and central cyclo-octane rings show chair, half-chair and boat-chair forms, respectively. There are three intra-molecular C-H⋯O inter-actions supporting the mol-ecular conformation, with one S(6) and two S(7) graph-set motifs. In the crystal, inter-molecular O-H⋯O hydrogen bonds connect the mol-ecules into a helical chain running along the c-axis direction, generating a C(7) graph-set motif. The chains are further linked by inter-molecular C-H⋯O inter-actions to construct a three-dimensional network. There is no valid C-H⋯π inter-action.

Crystal structure of (±)-(7RS,8SR)-7-methyl-1,4-dioxa-spiro-[4.5]decane-7,8-diol

In the title compound, C9H16O4, the five-membered dioxolane ring adopts a twist conformation; two adjacent C atoms deviate alternately from the mean plane of other atoms by -0.297 (4) and 0.288 (4) Å. The spiro-fused cyclo-hexane ring shows a chair form. The hy-droxy group substituted in an axial position makes an intra-molecular O-H⋯O hydrogen bond with one of the O atoms in the cyclic ether, forming an S(6) ring motif. In the crystal, the O-H⋯O hydrogen bond involving the equatorial hy-droxy group connects the mol-ecules into a zigzag chain with a C(5) motif running along the c axis.

Crystal structure of (±)-(1SR,5SR,6SR,7SR,10SR,11SR,13SR)-13-benz-yloxy-7-meth-oxy-meth-oxy-11,15,18,18-tetra-methyl-3-oxo-2,4-dioxa-tetra-cyclo-[12.3.1.0(1,5).0(6,11)]octa-deca-14,16-dien-10-yl benzoate

In the title compound, C36H42O8, the dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of other atoms by -0.287 (5) and 0.174 (5) Å. The cyclo-hexane, cyclo-hexa-diene and central cyclo-octane rings show chair, half-chair and boat-chair forms, respectively. As a result of the strained ring system, the tetra-subsituted olefin in the cyclo-hexa-diene is skewed from an ideal planar structure. In the crystal, C-H⋯O hydrogen bonds connect the mol-ecules into a sheet parallel to (100). The sheets are further linked by other weak C-H⋯O and C-H⋯π inter-actions, forming a three-dimensional network.