N-Benzylidenenordehydroabietylamine

The title compound [systematic name: (1R,4aS,10aR,E)-N-benzylidene-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-amine], C26H33N, has been synthesized from nor-dehydroabietylamine and benzaldehyde. The two cyclohexane rings form a trans ring junction with classic chair and half-chair conformations, respectively, the two methyl groups are on the same side of tricyclic hydrophenanthrene structure. The dihedral angle between two benzene rings is 44.2 (4)°. The C=N bond is in an E configuration.


Related literature
For the biological activity of dehydroabietiylamine derivatives, see: Rao et al. (2006)

Comment
Dehydroabietiylamine derivatives exhibit wide range of biological activities, such as antifungal and antitumor activity (Wilkerson et al., 1993 andRao et al., 2006). Nor-dehydroabietylamine is a new derivative of dehydoabietylamine, which the amine group directly attached to the tricyclic hydrophenthranene structure (Rao et al., 2006). Although much attention has been paid to the bioactivity of dehydroabietylamine derivatives, the crystal structure of the title compound has not yet been reported. In this work, we describe the crystal structure of the title compound.
As shown in Fig. 1, the title compound contains four rings, the two cyclohexane rings form a trans ring junction with classic chair and half-chair conformation, respectively, the two methyl groups are in the axis position of the cyclohexane ring. The two benzene rings are almost planar, the dihedral angle between them is 44.2 °. The bond lengths and bond angles in the molecule are in normal ranges. The title structure is compared with previously found structure 4-chloro-2-((E)-(((1R,4aS,10aR)-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenanthren-1-yl) methylimino)methyl)phenol (Rao et al.,2006). They exhibited almost the same configurations except that the imine group directly attached to the hydrophenanthrene structure of the title structure.

Experimental
A mixture of nor-dehydroabietylamine (1 mmol), benzaldehyde (1 mmol) and ethanol (20 ml) was stirred at 353 K for 4 h, then the solvent was distilled off. Upon recrystallization from acetone, white crystals of the title compound were obtained.
Single crystals were grown from acetone.

Refinement
H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.96Å and U iso (H) = 1.5U eq (C) for methyl H atoms, and C-H = 0.937-0.98Å and U iso (H) = 1.2U eq (C) for all other H atoms. In the absence of significant anomalous scattering effects, Friedel pairs were merged. Fig. 1. The molecular structure of the title compound, with H atoms represented by small spheres of arbitrary radius and displacement ellipsoids at the 30% probability level.

Special details
Experimental. Although the absolute configuration could not be determined in this case, it has been determined in our previous article which indicated the chiral centers exhibited R,S and R configurations, respectively. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.