The progress in enantioselective organocatalysis have enabled efficient and highly stereoselective syntheses of cyclobutane derivatives, through (2+2) annulation reactions, overcoming the geometrical constraints inherent to these small cyclic molecules. More importantly, taking advantage their strain-releasing fragmentation, some especially cyclobutanones cyclobutenones, can now be regarded as ...

The title compound, C(27)H(40)O(4), was obtained from the oxidation of (25R)-3b-hydr-oxy-5a-spiro-stan-12-one (Hecogenin) by Jone's reagent. The mol-ecule contains six alicyclic and heterocyclic rings, all trans-fused, among which four six-membered rings adopt similar chair conformations while two five-membered rings assume an envelope conformation.

The title compound, C16H22Cl2O, was synthesized from β-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-...

The title compound, C16H23Br3, was synthesized from β-himachalene (3,5,5,9-tetra-methyl-2,4a,5,6,7,8-hexa-hydro-1H-benzocyclo-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 from the reaction of himachalene with dibromo-carbene. The six-membered rin...

THE TITLE COMPOUND (SYSTEMATIC NAME 5,6β-dihy-droxy-1α,14α,16β-trimeth-oxy-4-methyl-7β,8-methyl-enedi-oxy-20-ethyl-aconitan-6-yl acetate acetone monosolvate), C(27)H(41)NO(8)·C(3)H(6)O, was isolated from Delphinium bonvalotii Franch, and is a typical C(19)-diterpenoid alkaloid. The mol-ecule has a lycoctonine carbon skeleton with four six-membered rings and three five-membered rings. Three six-...

The title compound, C(26)H(28)N(2)O(9)·1.5H(2)O, the product of an acid-catalysed Wagner-Meerwein skeletal rearrangement, crystallizes as a sesquihydrate with the O atom of one of the two independent water mol-ecules occupying a special position on a twofold axis. The organic mol-ecule comprises a fused penta-cyclic system containing two five-membered rings (cyclo-pentane and tetra-hydro-furan)...

The title compound, C(24)H(39)NO(6) [systematic name: (1α,6α,14α,16β)-N-ethyl-6,16-dimeth-oxy-4-meth-oxy-methylaconitane-1,8,14-triol], is a C(19)-diterpenoid alkaloid from the roots of Aconitum flavum Hand. The mol-ecule has an aconitane carbon skeleton with four six-membered rings and two five-membered rings. Both five-membered rings adopt envelope conformations. Two six-membered rings adopt ...

THE TITLE COMPOUND [SYSTEMATIC NAME: (1α,3α,6α,8β,13β,14α,16β)-20-ethyl-8-eth-oxy-3,13-dihy-droxy-1,6,16-trimeth-oxy-4-(meth-oxy-meth-yl)aconitan-14-yl 4-meth-oxy-benzoate], C(35)H(51)NO(10), was isolated from roots of Aconitum carmichaeli Debx., which is a typical C(19)-diterpenoid alkaloid. The mol-ecule has an aconitane carbon skeleton with four six-membered rings and two five-membered rings...

In the mol-ecule of the title compound, C(27)H(21)ClN(2)O(4), the dihedral angle between the furan rings is 67.00 (3)°. The chloro-phenyl ring is oriented at dihedral angles of 76.61 (3) and 69.36 (3)° with respect to the furan rings. An intra-molecular N-H⋯O inter-action results in the formation of an eight-membered ring with a twisted conformation. In the crystal structure, inter-molecular N-...

In the title compound, C18H23N5O4·CH2Cl2, the di-chloro-methane solvent mol-ecule is disordered over two sets of sites in a 0.630 (13):0.370 (13) ratio. The dihedral angle between the uracil and phenyl rings is 30.2 (1)°. In the crystal, the principal inter-actions are N-H⋯O hydrogen bonds, which link uracil units across centres of symmetry, forming eight-membered rings with an R (2) 2(8) graph...