In the search for cancer chemopreventive agents, we have studied the Diels-Alder reaction of trans-communic acid with tetra-cyano-ethyl-ene in the presence of SiO(2) as catalyst. The title cycloadduct, C(26)H(30)N(4)O(2), was obtained in 75% yield. The mol-ecules are arranged in pairs through O-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. Both the fused cyclohexyl rings adopt a chair ...

In the title compound, C(29)H(34)N(2)O(2), the central piperidine ring adopts a half-chair conformation, whereas the terminal one adopts a chair conformation. The mean plane of the central piperidine ring [maximum deviation = 0.384 (2) Å] makes dihedral angles of 64.82 (13) and 17.55 (13)° with the benzene rings. In the crystal, mol-ecules are linked into a tape along the b axis via C-H⋯O inter...

In the title compound, C24H29NO3, the aza-bicycle contains two six-membered rings, viz. a cyclo-hexane ring and a piperidine ring. The first adopts a chair conformation and the second a half-chair conformation. The dihedral angle between their mean planes is 86.21 (13)°, indicating that they are almost perpendicular to one another. The dihedral angle between the planes of the 4-meth-oxy-phenyl ...

Mol-ecules of the title compound, C(23)H(26)Cl(2)O(4), are linked by hydrogen bonds between the hydroxyl O atom and the carbonyl O atom of a neighboring mol-ecule. The central hydropyran and fused cyclohexanone rings adopt half-chair conformations, while the fused hydroxycyclohexanone ring adopts a chair conformation.

The mol-ecules of the two isotypic title compounds, C25H24BrN3, (I), and C25H24FN3, (II), comprise a 2-imino-pyridine ring fused with a cyclo-octane ring. In (I), the cyclo-octane ring adopts a twisted chair-chair conformation, while in (II), this ring adopts a twisted boat-chair conformation. The dihedral angles between the planes of the pyridine ring and the bromo-benzene and phenyl rings are...

In the title compound, C25H23Cl2N3, the cyclo-octene ring adopts a twist chair-chair conformation. The dihedral angles between the central pyridine ring (r.m.s. deviation = 0.013 Å) and the pendant chloro-benzene and benzyl rings are 78.07 (11) and 87.47 (12)°, respectively. No directional inter-actions could be identified in the crystal and the packing is governed by van der Waals inter-actions.

In the title compound, C(15)H(22)O(3), the five-membered ring displays an envelope conformation, whereas the two six-membered rings show different conformations, viz. chair and half-chair. In the crystal, mol-ecules are linked through inter-molecular O-H⋯O hydrogen bonds, forming chains running along the b axis.

The absolute configuration of the title compound, C16H23BrCl2, has been deduced from the chemical pathway and fully confirmed by refinement of the Flack and Hooft parameters. The six-membered ring adopts a half-chair conformation, whereas the seven-membered ring is a twisted chair. The mol-ecular packing within the crystal is stabilized only by van der Waals inter-actions.

The crystal structure of the title compound, C(23)H(27)NO(3), shows that the compound exists in a chair-chair conformation with an equatorial disposition of 2-methoxy-phenyl groups at an angle of 39.94 (3)° with respect to each other. An inter-molecular N-H⋯π inter-action is observed in the crystal packing.

THE TITLE COMPOUND (SYSTEMATIC NAME 3-meth-oxy-24-methyl-9,19-cyclo-lanost-25-ene), C(32)H(54)O, is a triterpenoid which has been isolated from Skimmia laureola. The three six-membered rings adopt chair, slightly distorted half-chair and distorted boat conformations, and the five-membered ring adopts an envelope conformation. All the rings are trans fused.