Synthesis of Novel Nitro-Halogenated Aryl-Himachalene Sesquiterpenes from Atlas Cedar Oil Components: Characterization, DFT Studies, and Molecular Docking Analysis against Various Isolated Smooth Muscles.

We report the synthesis of two novel halogenated nitro-arylhimachalene derivatives: 2-bromo-3,5,5,9-tetramethyl-1-nitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (bromo-nitro-arylhimachalene) and 2-chloro-3,5,5,9-tetramethyl-1,4-dinitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (chloro-dinitro-arylhimachalene). These compounds were derived from arylhimachalene, an important sesquiterpene component of Atlas cedar essential oil, via a two-step halogenation and nitration process. Characterization was performed using 1H and 13C NMR spectrometry, complemented by X-ray structural analysis. Quantum chemical calculations employing density functional theory (DFT) with the Becke3-Lee-Yang-parr (B3LYP) functional and a 6-31++G(d,p) basis set were conducted. The optimized geometries of the synthesized compounds were consistent with X-ray structure data. Frontier molecular orbitals and molecular electrostatic potential (MEP) profiles were identified and discussed. DFT reactivity indices provided insights into the compounds' behaviors. Moreover, Hirshfeld surface and 2D fingerprint analyses revealed significant intermolecular interactions within the crystal structures, predominantly H-H and H-O contacts. Molecular docking studies demonstrate strong binding affinities of the synthesized compounds to the active site of protein 7B2W, suggesting potential therapeutic applications against various isolated smooth muscles and neurotransmitters.

Crystal structure of (1S,3R,8R,9R,10S)-2,4,6-tris-(2,2-di-chloro-3,7,7,10-tetra-methyl-tri-cyclo-[6.4.0.0(1,3)]dodec-9-yl)cyclo-triboroxane.

The title compound, C48H75B3Cl6O3, was synthesized in two steps from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-hept-ene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The mol-ecule consists of an almost planar cyclo-triboroxane ring [maximum deviation = 0.036 (2) Å] linked to three identical fused ring systems with different conformations. Each of the three attached ring systems is built up from a seven-membered ring to which a six- and a three-membered ring are fused. The three six-membered rings have a twist-boat conformation, whereas the seven-membered rings display boat, chair and twist-boat conformations. The dihedral angles between the central boroxane ring and the mean planes of the attached six-membered rings are 63.67 (18), 54.89 (2) and 56.57 (19)°. The crystal packing is governed only by van der Waals inter-actions.

Crystal structure of 1-isopropyl-4,7-dimethyl-3-nitro-naphthalene.

The title compound, C15H17NO2, was synthesized from a mixture of α-himachalene (2-methyl-ene-6,6,9-tri-methylbi-cyclo-[5.4.0(1,7)]undec-8-ene) and ß-himachalene (2,6,6,9-tetra-methylbi-cyclo-[5.4.0(1,7)]undeca-1,8-diene), which were isolated from an oil of the Atlas cedar (Cedrus Atlantica). The naphthalene ring system makes dihedral angles of 68.6 (2) and 44.3 (2)°, respectively, with its attached isopropyl C/C/C plane and the nitro group. In the crystal, mol-ecules held together by a C-H⋯O inter-action, forming a chain along [-101].

Crystal structure of ethyl 2-(1H-benzimidazol-2-yl)-2-[2-(4-nitro-phen-yl)hydrazinyl-idene]acetate.

The title compound, C17H15N5O4, was obtained via the condensation of 3-eth-oxy-2-[2-(4-nitro-phen-yl)hydrazono]-3-oxo-propanoic acid with 1,2-di-amino-benzene. In the mol-ecule, the dihedral angles between the acetate group and the two aromatic subunits (benzimidazole and nitro-phenyl-hydrazone) are 7.35 (9) and 18.23 (9)°, respectively. Intra-molecular N-H⋯O and N-H⋯N contacts occur. In the crystal, C-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into chains along the b-axis direction.

Crystal structure of (1S,3R,8R,9S,10R)-10-bromo-methyl-2,2-di-chloro-9,10-ep-oxy-3,7,7-tri-methyl-tri-cyclo-[6.4.0.0(1,3)]dodeca-ne.

The title compound, C16H23BrCl2O, was synthesized in three steps from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (cedrus atlantica). The mol-ecule is built up from two fused six- and seven-membered rings, each linked to a three-membered ring. The six-membered ring has a screw-boat conformation, whereas the seven-membered ring displays a twist-boat conformation. The absolute structure was established unambiguously from anomalous dispersion effects.

Crystal structure of (1S,2R,4R,9S,11S,12R)-9α-hy-droxy-4,8-dimethyl-12-[(thio-morpholin-4-yl)meth-yl]-3,14-dioxatri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one.

The title compound, C19H29NO4S, was synthesised from 9α-hy-droxy-parthenolide (9α-hy-droxy-4,8-dimethyl-12-methyl-ene-3,14-dioxatri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one), which was isolated from the chloro-form extract of the aerial parts of the plant Anvillea radiata. The mol-ecule is built up from two fused five- and ten-membered rings, with an additional ep-oxy ring system and a thio-morpholine group as a substituent. The ten-membered ring adopts an approximate chair-chair conformation, while the thio-morpholine ring displays a chair conformation and the five-membered ring has an envelope conformation, with the C atom closest to the hy-droxy group forming the flap. An intra-molecular O-H⋯N hydrogen bond closes an S(8) ring. The crystal structure features weak C-H⋯O hydrogen-bonding inter-actions, which link the mol-ecules into [010] chains.

(1R,4R,6S,7R)-5,5-Di-bromo-1,4,8,8-tetra-methyl-tri-cyclo-[5.4.1.0(4,6)]dodecan-12-one.

The title compound, C16H24Br2O, was synthesized from the reaction of ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from Atlas cedar (Cedrus atlantica). The asymmetric unit contains two independent mol-ecules with similar conformations. Each mol-ecule is built up from two fused seven-membered rings and an additional three-membered ring. In both mol-ecules, one of the seven-membered rings has a chair conformation, whereas the other displays a screw-boat conformation.

9α-Hy-droxy-12-{[4-(4-hy-droxy-phen-yl)piperazin-1-yl]meth-yl}-4,8-dimethyl-3,14-dioxatri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one.

The title compound, C25H34N2O5, was synthesized from 9α-hy-droxy-parthenolide (9α-hy-droxy-4,8-dimethyl-12-methylen-3, 14-dioxa-tri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one), which in turn was isolated from the chloro-form extract of the aerial parts of Anvillea radiata. The mol-ecule comprises a ten-membered ring fused to a five-membered ring with an additional ep-oxy ring system fused to the ten-membered ring. The five-membered ring also carries a 4-hy-droxy-phenyl-piperazin-1-ylmethyl substituent. The ten-membered ring adopts an approximate chair-chair conformation, while the piperazine ring displays a chair conformation and the five-membered ring shows an envelope conformation with the C atom closest to the hy-droxy group forming the flap. Two C atoms in the phenyl ring and the O atom of the hydroxyl group are disordered over two sites, with an occupancy ratio of 0.53 (5):0.47 (5). An intra-molecular O-H⋯N hydrogen-bond stabilizes the mol-ecular conformation. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into zigzag chains running along the a-axis direction.

(1S,2R,3S,6S,7R)-3,7,11,11-Tetra-methyl-6,7-epoxybi-cyclo-[5.4.0]undecane-2-ol.

The title compound, C15H26O2, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the Atlas cedar (cedrus atlantica). The mol-ecule is built up from a seven-membered ring to which a six- and a three-membered ring are fused. The seven- and six-membered rings each have a twist-boat conformation. In the crystal, O-H⋯O hydrogen bonds link the mol-ecules into zigzag chains running along the b-axis direction.

1-[(1S,6R,7S,9R)-8,8-Di-bromo-5,5,9-tri-methyl-tri-cyclo-[4.4.0.1(7,9)]decan-1-yl]ethanone.

The title compound, C16H24Br2O, was synthesized by three steps from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from essential oil of the Atlas cedar cedrus atlantica. The asymmetric unit contains two independent mol-ecules with almost identical conformations. Each mol-ecule is built up from two fused six-membered rings, one having a chair conformation and the other a boat conformation, and an additional three-membered ring arising from the reaction of himachalene with di-bromo-carbene. In the crystal, there are no significant intermolecular interactions present. The absolute structure of the title compound was confirmed by resonance scattering.

12-{[4-(4-Bromo-phen-yl)piperazin-1-yl]meth-yl}-9α-hy-droxy-4,8-dimethyl-3,14-dioxatri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one.

The title compound, C25H33BrN2O4, was synthesized from 9α-hy-droxy-parthenolide (9α-hy-droxy-4,8-dimethyl-12-methylen-3,14-dioxa-tri-cyclo-[9.3.0.0(2,4)]tetra-dec-7-en-13-one), which was isolated from the chloro-form extract of the aerial parts of Anvillea radiata. The mol-ecule is built up from two fused five- and ten-membered rings with an additional ep-oxy ring system and a bromo-phenyl-piperazine group as a substituent. The ten-membered ring adopts an approximate chair-chair-chair conformation, while the piperazine ring displays a chair conformation and the five-membered ring shows an envelope conformation with the C atom closest to the hy-droxy group forming the flap. An intra-molecular O-H⋯N hydrogen bond stabilizes the mol-ecular conformation. The crystal packing features C-H⋯O hydrogen bonds, which link the mol-ecules into zigzag chains running along the b-axis direction.

(1S,3S,8R,9S,11R)-10,10-Di-bromo-3,7,7,11-tetra-methyl-tetra-cyclo-[6.5.0.0(1,3).0(9,11)]trideca-ne.

The title compound, C17H26Br2, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The asymmetric unit contains two independent mol-ecules with similar conformations. Each mol-ecule is built up from fused six- and seven-membered rings and two appended three-membered rings. In both mol-ecules, the six-membered ring has a screw boat conformation, whereas the seven-membered ring displays a boat conformation. No specific inter-molecular inter-actions were discerned in the crystal packing.

(1S,3R,8R,11S)-11-Bromo-10-bromo-methyl-2,2-di-chloro-3,7,7-tri-methyl-tricyclo-[6.4.0.0(1,3)]dodec-9-ene.

The title compound, C16H22Br2Cl2, was synthesized from ß-him-achalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The mol-ecule is built up from fused six- and seven-membered rings and an appended three-membered ring. The six-membered ring has a half-chair conformation, whereas the seven-membered ring displays a chair conformation. The dihedral angle between the two best plane through each ring is 59.5 (2)°. No specific inter-molecular inter-actions were discerned in the crystal packing.

1,10,10-Trimethyl-5-phenyl-3-oxa-4-aza-tri-cyclo-[5.2.1.0(2,6)]dec-4-en-2-ol.

The title compound, C17H21NO2, was synthesized by the reaction of (1R)-(+)-3-benzyl-camphor and hydroxyl-amine. The oxazole ring makes a dihedral angle of 23.42 (16)° with the phenyl ring. The six-membered ring of the norboryl group adopts a boat conformation, whereas each of the five-membered rings of the norboryl group displays a flattened envelope conformation, with the C atom carrying the methyl groups representing the flap for both rings. In the crystal, mol-ecules are linked into zigzag chains propagating along the b axis by O-H⋯N hydrogen bonds.

(1S,3S,8R,10R,11R)-3,7,7,10-Tetra-methyl-tri-cyclo-[6.4.0.0(1,3)]dodecan-11-ol.

The title compound, C16H28O, was synthesized by three steps from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus atlantica). The mol-ecule is built up from fused six- and seven-membered rings and an appended three-membered ring. The six-membered ring has twist-boat conformation, whereas the seven-membered ring displays a chair conformation. In the crystal, mol-ecules are linked into chains propagating along the a-axis direction by O-H⋯O hydrogen bonds.

(1S,2R,7R,8S,10R)-9,9-Di-bromo-2,6,6,10-tetra-methyl-1α,2α-ep-oxy-tri-cyclo-[5.5.0.0(8,10)]dodeca-ne.

The title compound, C16H24Br2O, was synthesized from the reaction of ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from Atlas cedar (Cedrus atlantica) essential oil, after reaction with di-bromo-carbene. The asymmetric unit contains two independent mol-ecules with similar conformations. Each mol-ecule is built up from fused six-and seven-membered rings and two three-membered rings. In both mol-ecules, the six-membered ring has an envelope conformation with the flap provided by the C atom of the ep-oxy ring, whereas the seven-membered ring displays a chair conformation. The crystal packing is governed only by van der Waals inter-actions. The absolute configuration was established from anomalous dispersion effects.

(1S,3R,8R)-2,2-Di-chloro-3,7,7,10-tetra-methyl-tri-cyclo-[6.4.0.0(1,3)]dodec-9-en-11-one.

The title compound, C16H22Cl2O, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The mol-ecule is built up from fused six- and seven-membered rings and an additional three-membered ring arising from the reaction of himachalene with di-chloro-carbene. The six-membered ring has an envelope conformation, with the C atom belonging to the three-membered ring forming the flap, whereas the seven-membered ring displays a screw-boat conformation; the dihedral angle between the rings (all atoms) is 59.65 (14)°.

(1S,3S,8R,9S,11R)-10,10-Di-chloro-3,7,7,11-tetra-methyl-tetra-cyclo[6.5.0.0(1,3).0(9,11)]trideca-ne.

The title compound, C17H26Cl2, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The asymmetric unit contains two independent mol-ecules with similar conformations. Each mol-ecule is built up from fused six- and seven-membered rings and two three-membered rings from the reaction of ß-himachalene with di-chloro-carbene. In both mol-ecules, the six-membered ring has a half-chair conformation, whereas the seven-membered ring displays a boat conformation. The absolute configuration was established from anomalous dispersion effects.

(1S,3R,8R,9S,11R)-2,2-Di-bromo-10,10-di-chloro-3,7,7,11-tetra-methyl-tetra-cyclo-[6.5.0.0(1,3).0(9,11)]trideca-ne.

The title compound, C17H24Br2Cl2, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The mol-ecule contains fused six-, seven- and two three-membered rings. The six-membered ring has a half-chair conformation, while the seven-membered ring displays a boat conformation. The absolute structure was unambiguously established from anomalous dispersion effects. The crystal packing exhibits no short inter-molecular contacts.

(1S,3R,8R,9S,11R)-10,10-Di-bromo-2,2-di-chloro-3,7,7,11-tetra-methyl-tetra-cyclo-[6.5.0.0(1,3).0(9,11)]trideca-ne.

The title compound, C17H24Br2Cl2, was synthesized from ß-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzo-cyclo-heptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The asymmetric unit contains two independent mol-ecules. Each mol-ecule is built up from fused six-, seven- and two three-membered rings. In both mol-ecules, the six-membered ring has a half-chair conformation, whereas the seven-membered ring displays a boat conformation. No specific inter-molecular inter-actions are noted in the crystal packing.