Essediya Lassaba

2α,3α:6α,7α-Diépoxyhimachalane

The stereochemistry of the minor isomer, 3,4: 9,9a-diepoxy-3,5,5,9-tetramethyldecahydro- 1H-benzocyclo-heptene, C15H2402, resulting from the epoxidation of β-himachalene has been established. The atoms C10 and the gem-dimethyl groups C14 and C15 adopt two positions leading to two conformations for the seven-membered ring, boat-shaped (occupation factor 70%) and chair-shaped (30%). Modelling of these conformations agrees with the statistical distribution in the crystal.

2α,3α:7α,8α-Diépoxy-cis-himachalane

The stereochemistry of the major isomer resulting from the epoxidation of γ-cis-himachalene has been established as 2α,3α:7α,8α-diepoxy-γ-cis-himachalene, C 15 H 24 O 2 . Hence, the configurations of the two resulting derivatives have been deduced. The seven-membered ring is twist-chair shaped while the six-membered ring adopts a 1,2-diplanar conformation.

(1S,3R,8R)-2,2-Dibromo-3,7,7,10-tetra­methyl­tricyclo­[6.4.0.01,3]dodec-9-ene

The title compound, C16H24Br2, was synthesized from β-himachalene (3,5,5,9-tetramethyl-2,4a,5,6,7,8-hexahydro-1H-benzocycloheptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The molecule is built up from two fused six- and seven-membered rings and an additional three-membered ring from the reaction of β-himachalene with dibromocarbene. The six-membered ring shows a screw-boat conformation, whereas the seven-membered ring displays a boat conformation; the dihedral angle between the mean planes through the rings is 57.9 (4)°. The absolute structure was established unambiguously from anomalous dispersion effects.

Cyclopropanation reactions on α-cis-himachalene and a β-himachalene

The crystallographic structures of 2a,3a,7a,15a-tetrabromocarbene-himachalane, C17H24Br4, (3), 2a,3a,7a,15a-tetrachlorocarbene-himachalane, C17H24Cl4, (4), and 6a,7a-dichlorocarbene-himachal-2-ene, C16H24Cl2, (5), resulting from cyclopropanation reactions of the C═C double bonds of α-cis-himachalene and β-himachalene, are reported.

Cyclopropanation of a β-himachalene monoepoxide derivative

The stereochemistry of the title compound, (1S,2R,7S-8S, 10R)-9,9-dichloro-1,2-epoxy-2,6,6,10-tetramethyltricyclo[5.5.0.0. 8,10 ]dodecane, C 16 H 24 Cl 2 O, a derivative of β-himachalene, has been established. The epoxide bridge located at positions 1 and 2 on the seven-membered ring adopts a cis conformation with respect to the cyclopropane bridge located at positions 8 and 10 on the six-membered ring.

2α,3α:7β,13β-Diépoxy-trans-himachalane

The stereochemistry of the major isomer resulting from the epoxidation of α-trans-himachalene has been established. Hence, the configurations of the three resulting derivatives have been deduced. The seven-membered ring in the title compound, C 15 H 24 O 2 , is twist-chair shaped while the six-membered ring adopts a 1,2-diplanar conformation.

7-Hy­droxy-8-isopropyl-1,1,4a-trimethyl-4a,9,10,10a-tetra­hydro-phenanthren-2(1H)-one

The title compound, C20H26O2, was isolated from a chloroform extract of Tetraclinis articulata wood. The molecule contains three fused rings which exhibit different conformations. The non-aromatic oxo-substituted ring has a screw-boat conformation, while the central ring has a half-chair conformation. In the crystal, molecules are linked to each other by intermolecular O—H⋯O hydrogen bonds involving the carbonyl and hydroxy groups.

2-Acetyl-3,5,5,9-tetra­methyl-6,7,8,9-tetra­hydro-5H-benzocyclo­hepten-7-one

The title compound, C17H22O2, was semi-synthesized from a mixture of α-atlantone (Z) and α-atlantone (E), which were isolated from the essential oil of the Atlas cedar (cedrus atlantica). The molecule consists of fused six- and seven-membered rings. The seven-membered ring is in a screw-boat conformation.

3β-Acetoxy-elemo-lanost-8-en-24-one

The sodium periodate is prepared in situ with a equimolecular quantity of soda NaOH (0.5g; 12.50 mmol) and periodic acid H5IO6 (2.85g; 12.50 mmol), the mixture is stirred at 0°C. After 15 min, 5 ml of CCl4, 5 ml of H3CCN and 93.03mg (0.12mmol) of ruthenium trichloride1,2 were added.[...]

4α,14α,Dimethyl-5α-cholest-8-en-3-one thiadiazoline

The compound 2 (0.21g, 0.25mmol) was dissolved in 1ml of pyridine and 1ml of acetic anhydride1,2.[...]