9-(Dicyano­methyl­idene)fluorene-tetra­thia­fulvalene (1/1)

The title compound, C₁₆H₈N₂·C₆H₄S₄, crystallizes with the fluorene derivative placed in a general position and two half tetra­thia­fulvalene (TTF) mol­ecules, each completed to a whole mol­ecule through an inversion center. The fluorene ring system is virtually planar (r.m.s. deviation from the mean plane = 0.027 Å) and the dicyano group is twisted from the fluorene plane by only 3.85 (12)°. The TTF mol­ecules are also planar, and their central C=C bond lengths [1.351 (8) and 1.324 (7) Å] compare well with the same bond length in neutral TTF (ca 1.35 Å). These features indicate that no charge transfer occurs between mol­ecules in the crystal; the compound should thus be considered a cocrystal rather than an organic complex. This is confirmed by the crystal structure, in which no significant stacking inter­actions are observed between mol­ecules.

Diaqua­tris­(nitrato-κ²O,O′){2,2′-[pyridine-2,6-diylbis(methyl­ene­oxy)]dibenzaldehyde-κO¹}dysprosium(III)–2,2′-[pyridine-2,6-diylbis(methyl­ene­oxy)]dibenzaldehyde (1/1)

The title compound, [Dy(NO₃)₃(C₂₁H₁₇NO₄)(H₂O)₂]·C₂₁H₁₇NO₄, may be considered as an organic–metalorganic 1:1 co-crystal, in which the two dialdehyde mol­ecules act as a ligand and as an organic moiety, respectively. The Dy^III atom coordinates nine O atoms from the organic ligand, bidentate nitrate ions and water mol­ecules, approximating a square-face-tricapped trigonal–prismatic geometry. The coordinated dialdehyde is not planar: the uncoordinated oxybenzaldehyde group is twisted by 39.96 (4)° from the rest of the ligand. In contrast, the free organic moiety is almost planar, with an r.m.s. deviation of 0.15 Å. In the crystal, segregated stacks of dialdehyde are formed in the [100] direction. For the complex, the shortest π–π contact is found at 3.781 (2) Å, and for the free ligand, at 3.785 (2) Å. The crystal structure is further stabilized by O—H...O and O—H...N hydrogen bonds in which coordinated water mol­ecules are the donor groups.

Tris[2-(2H-indazol-2-yl)eth­yl]amine

The title tertiary amine, C₂₇H₂₇N₇, a potential tripodal ligand for coordination chemistry, crystallizes with the central N atom located on a threefold axis of a trigonal cell. The gauche conformation of the N(amime)—CH₂—CH₂—N(indazole) chain [torsion angle = −64.2 (2)°] places the pendant 2H-indazole heterocycles surrounding the symmetry axis, affording a claw-like shaped mol­ecule. Two symmetry-related indazole planes in the mol­ecule make an acute angle of 60.39 (4)°. The lone pair of the tertiary N atom is located inside the cavity, and should thus be inactive (as a ligand). In the crystal, neither significant π–π nor C—H...π inter­actions between molecules are found.

Diosgenin hemihydrate

Diosgenin [or (22R,25R)-spirost-5-en-3β-ol] is the starting material of the Marker degradation, a cheap semi-synthesis of progesterone, which has been designated as an Inter­national Historic Chemical Landmark. Thus far, a single X-ray structure for diosgenin is known, namely its dimethyl sulfoxide solvate [Zhang et al. (2005). Acta Cryst. E61, o2324–o2325]. We have now determined the structure of the hemihydrate, C₂₇H₄₂O₃·0.5H₂O. The asymmetric unit contains two diosgenin mol­ecules, with quite similar conformations, and one water mol­ecule. Hy­droxy groups in steroids and water mol­ecules form O—H...O hydrogen-bonded R₅⁴(10) ring motifs. Fused edge-sharing R(10) rings form a backbone oriented along [100], which aggregates the diosgenin mol­ecules in the crystal structure.

Diosgenone: a second P2₁ polymorph

Diosgenone [(20S,22R,25R)-spirost-4-en-3-one, C₂₇H₄₀O₃] has been proposed as a new therapeutic alternative for the treatment of malaria. The first X-ray structure report for diosgenone was by Piro et al. [(2002). Z. Naturforsch. Teil C, 57, 947–950] in the space group P2₁ (Z′ = 2). We now report a new polymorph in the same space group, with two mol­ecules in the asymmetric unit. Both mol­ecules have similar conformations, characterized by a skewed envelope A ring, which contains the C=C bond conjugated with the ketone functionality at C3. The dimorphism results from a modification of the relative orientation of the mol­ecules in the asymmetric unit: two independent mol­ecules were arranged anti­parallel in the Piro report, while they are parallel in the present determination.

4,4′-[(2R*,3R*,4R*,5R*)-3,4-Dimethyl­tetra­hydro­furan-2,5-di­yl]diphenol

The title mol­ecule, C₁₈H₂₀O₃, is a furan­oid lignan extracted from the leaves of Larrea tridentata. The relative absolute configuration for the four chiral centers was established, showing that this compound is 4-epi-larreatricin, which has been previously reported in the literature. The mol­ecule displays noncrystallographic C₂ symmetry, with the methyl and phenol substituents alternating above and below the mean plane of the furan ring. The conformation of this ring is described by the pseudorotation phase angle P = 171.3° and the maximum out-of-plane pucker ν_m = 37.7°. These parameters indicate that the furan ring adopts the same conformation as the ribose residues in B-DNA. The packing is dominated by inter­molecular O—H...O hydrogen bonds. The phenol hy­droxy groups form chains in the [110] direction and these chains inter­act via O—H...O(furan) contacts.

3-tert-Butyl 5-methyl (2R,4S,5R)-2-(4-methoxyphenyl)-4-(3-nitrophenyl)-1,3-oxazolidine-3,5-dicarboxylate

The title mol­ecule, C₂₃H₂₆N₂O₈, was synthesized in three steps starting from m-nitro­cinnamic acid. The central oxazolidine ring adopts an almost perfect envelope conformation with the O atom as the flap [puckering parameter φ = 0.3 (6)°]. The dihedral angle formed by the benzene rings is 61.81 (9)°. In the crystal, mol­ecules are connected into double chains parallel to [010] by C—H...O hydrogen bonds. The absolute configuration was assigned from the synthetic procedure.

Westphalen's diol diacetate: 19(10→5)-abeo-5β-cholest-9-ene-3β,6β-diyl diacetate

The structure of the title steroid [alternative name: 3β,6β-diacet­oxy-5β-methyl-19-norcholest-9(10)-ene], C₃₁H₅₀O₄, confirms the generally accepted mechanism for the rearrangement of a cholestan-5α-ol derivative reported a century ago by Westphalen. The methyl group at position 10 of the starting material migrates to position 5 in the steroidal nucleus, while a Δ⁹ bond is formed, as indicated by the C=C bond length of 1.347 (4) Å. The methyl transposition leaves the 5R configuration unchanged, with the methyl oriented towards the β face. During the rearrangement, the steroidal B ring experiences a conformational distortion from chair to envelope with the C atom at position 6 as the flap. In the title structure, the isopropyl group of the side chain is disordered over two positions, with occupancies of 0.733 (10) and 0.267 (10). The carbonyl O atom in the acetyl group at C3 is also disordered with an occupancy ratio of 0.62 (4):0.38 (4).

(25R)-6α-Hy­droxy-5α-spiro­stan-3β-yl tosyl­ate

The title steroid, C₃₄H₅₀O₆S, is an inter­mediate on the synthetic route between diosgenin and brassinosteroids, which possess the A ring modified with the 2α,3α-diol functionality. The polycyclic spiro­stan system has the expected conformation, with six-membered rings adopting chair forms and the five-membered rings envelope forms (flap atoms are the methine C atom in the C/D-ring junction and the spiro C atom connecting rings E and F). The 3β-tosyl­ate group is oriented in such a way that S=O bonds are engaged in inter­molecular hydrogen bonds with O—H and C—H donors. Chains of mol­ecules are formed along [100] via O—H...O hydrogen bonds, and secondary weak C—H...O inter­actions connect two neighbouring chains in the [001] direction.