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The title compounds, C 38 H 48 O 11 ( 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., (© Oishi et al. 2025.)

In the fused tetra-cyclic system of the title compound, C 29 H 36 O 9 , 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., (© Oishi et al. 2021.)

In the title compound, C 20 H 27 NO 6 , the amide moiety is essentially planar, with a maximum deviation of 0.073 (3) Å, and one of the N -methyl groups shows rotational disorder. The five-membered 1,3-dioxolane ring adopts an envelope form, with the C atom bonded to the olefin side chain as the flap, which deviates from the mean plane through the other four atoms by 0.564 (7) Å. The 1,3-dioxole ring fused to the benzene ring adopts a flattened envelope form, with the C atom between the two O atoms as the flap, which deviates from the mean plane through the other four atoms by 0.215 (7) Å. The C-C=C-C olefin moiety is essentially planar and makes a dihedral angle of 87.1 (3)° with the benzene ring. An intra-molecular O-H⋯O hydrogen bond supports the mol-ecular conformation, enclosing an S (11) graph-set motif. In the crystal, inter-molecular C-H⋯O hydrogen bonding links the mol-ecules into a tape running along the b axis. Furthermore, other weak C-H⋯O hydrogen bonds and a C-H⋯π inter-action connect the tapes into a sheet structure parallel to (100).

The title compound, C 17 H 23 NO 4 ·H 2 O, is an epimer of the natural tetra-cyclic alkaloid isosaxorumamide which consists of a fused 5-7-5 tricyclic core and a di-hydro-furan-one substituent. The terminal di-hydro-furan ring is essentially planar with a maximum deviation of 0.0273 (14) Å from the mean plane and oxolane, azepane and pyrrolidine rings in the tricyclic ring system adopt twist, twist-chair and envelope forms, respectively. In the crystal, the amide and water mol-ecules are linked by O-H⋯O hydrogen bonds, forming a tape structure running along the b- axis direction. The tapes are further connected by C-H⋯O inter-actions into a three-dimensional architecture.

In the title compound, C 10 H 14 Cl 3 NO 5 , the five-membered dioxolane ring adopts an envelope conformation with the C atom bonded to the butenoate side chain as the flap. It deviates from the mean plane of the other atoms in the ring by 0.446 (6) Å. In the crystal, mol-ecules are connected by O-H⋯O hydrogen bonds into helical chains running along the b- axis direction. The chains are linked into a sheet structure parallel to (001) by an N-H⋯O hydrogen bond. These classical hydrogen bonds enclose an R 4 4 (24) graph-set motif in the sheet structure. Furthermore, a weak inter-molecular C-H⋯Cl inter-action expands the sheet structures into a three-dimensional network.

In the title compound, C12H19NO6, the six-membered 1,3-dioxane ring adopts a chair-like conformation. The seat of this chair, containing two O atoms, is essentially planar, with a maximum deviation of 0.0021 (12) Å. The five-membered oxolane ring cis-fused to the 1,3-dioxane ring adopts an envelope form. The bridgehead C atom at the flap, which is bonded to the tetra-substituted C atom of the oxolane ring, deviates from the mean plane of other ring atoms by 0.539 (4) Å. In the crystal, classical O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into a sheet structure enclosing an R 4 (4)(24) graph-set motif. Weak inter-molecular C-H⋯O inter-actions support the sheet formation.

In the title compound, C10H14Cl3NO5, the five-membered dioxolane ring adopts an envelope conformation. The C atom at the flap, which is bonded to the hy-droxy-methyl substituent, deviates from the mean plane of other ring atoms by 0.357 (5) Å. There are two intra-molecular hydrogen bonds (O-H⋯N and N-H⋯O) between the hy-droxy and amino groups, so that O- and N-bound H atoms involved in these hydrogen bonds are each disordered with equal occupancies of 0.50. The methyl 2-methyl-prop-2-enoate substituent also shows a disordered structure over two sets of sites with refined occupancies of 0.482 (5) and 0.518 (5). In the crystal, mol-ecules are connected into a dimer by an O-H⋯O hydrogen bond. The dimers are further linked by N-H⋯O, C-H⋯N and C-H⋯O inter-actions, extending a sheet structure parallel to ([Formula: see text]01).

In the title compound, C19H25NO2, the pyrrolidine ring adopts an envelope form, with the spiro C atom as the flap, while the cyclo-hexane ring shows a chair form. A weak intra-molecular C-H⋯O inter-action supports the mol-ecular conformation, generating an S(6) ring motif. In the crystal, pairs of C-H⋯O inter-actions connect the mol-ecules into inversion dimers with an R 2 (2)(16) ring motif. The dimers are linked by a second pair of C-H⋯O inter-actions, enclosing an R 4 (2)(12) ring motif, into a tape structure along the b axis.

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.

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.

The title compounds, C29H38O8·0.25C5H12, (A), C29H38O8, (B), and C29H36O8, (C), are tetra-cyclic 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 mol-ecules (A and A') and a half mol-ecule of solvent pentane disordered about an inversion center. The mol-ecular conformations of (A), (B) and (C) are similar except for the flexible meth-oxy-meth-oxy group. The cyclo-hexane, cyclo-hexene and central cyclo-octane 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), inter-molecular O-H⋯O, C-H⋯O and C-H⋯π inter-actions link the independent benzoates alternately, forming a chain structure. In the crystals of (B) and (C), mol-ecules are linked through O-H⋯O and C-H⋯π inter-actions, and C-H⋯O hydrogen bonds, respectively, into similar chains. Further, weak inter-molecular C-H⋯O inter-actions connect the chains into a three-dimensional network in (A) and a sheet in (B), whereas no other interactions are observed for (C).

In the title compound, C36H44O10·C6H6, the dioxolane ring adopts an envelope conformation with the C atom bonded to the H atom as the flap, while the cyclo-hexene and cyclo-hexane rings are in half-chair and chair conformations, respectively. In the crystal, a pair of O-H⋯O hydrogen bonds with an R 2 (2)(26) graph-set motif connect the benzoate mol-ecules into an inversion dimer. The dimers are linked by a weak C-H⋯O inter-action into a tape structure along [01-1]. The benzene mol-ecule links the tapes through C-H⋯O and C-H⋯π inter-actions, forming a sheet parallel to (100).