The title compound, C(45)H(34)O(4), is the product of a tandem 'pincer' Diels-Alder reaction consisting of two consecutive [4 + 2] cyclo-additions between two 2-benzofuran units and ethyl propiolate. The mol-ecule comprises a fused hexa-cyclic system containing four five-membered rings, which are in the usual envelope conformation, and two six-membered rings. In addition, four phenyl rings are ...

The title compound, C(20)H(30)O(2), is an ent-atisane diterpenoid which was isolated from the roots of Euphorbia kansuensis. The mol-ecule contains five six-membered rings, among which three six-membered rings of the bicyclo-[2.2.2]octane unit adopt boat conformations and two cyclo-hexane rings adopt chair conformations. In the crystal structure, mol-ecules are connected by inter-molecular O-H⋯...

The title compound, C(30)H(50)O(3), which was isolated from a marine endophytic fungus, is a new friedelan derivative. The mol-ecule contains five six-membered rings, which exhibit boat (ring A), distorted boat (ring B) and chair (rings C-E) conformations. The crystal structure is stabilized by inter-molecular O-H⋯O hydrogen bonds, which link neighbouring mol-ecules into 12-membered rings.

In the title compound, C24H18S, the dihedral angles between the phenyl ring and the two benzene rings of the anthracene moiety are 51.92 (9) and 68.24 (9)°, whereas the dihedral angle between the two anthracene benzene rings is 120.13 (9)°. The three non-aromatic six-membered rings are in boat conformations, while the five-membered ring has an envelope conformation on the S atom. In the crystal...

THE TITLE COMPOUND (SYSTEMATIC NAME 8β-acet-oxy-14α-benzo-yloxy-N-ethyl-13β,15α-dihydr-oxy-1α,6α,16β-trimeth-oxy-4β-methoxy-methyl-eneaconitane), C(34)H(47)NO(10), is a typical aconitine-type C(19)-diterpenoid alkaloid, and was isolated from the roots of the Aconitum carmichaeli Debx. The mol-ecule has an aconitine carbon skeleton with four six-membered rings and two five-membered rings, whose ...

In the mol-ecule of the title compound, C(17)H(20)FN(3)O(4)S, the pyrimidine and benzene rings are oriented at a dihedral angle of 35.59 (3)°. Intra-molecular C-H⋯N and C-H⋯O hydrogen bonds result in the formation of one five- and two six-membered non-planar rings. One of the six-membered rings adopts a chair conformation, while the other six-membered ring and the five-membered ring exhibit env...

An efficient method for the asymmetric gold(I)-catalyzed preparation of medium sized rings has been developed. The method provides 7- to 9-membered rings in excellent yield. High enantioselectivities can be achieved for 7- and 8-membered ring products employing chiral gold(I) complexes. The results provide insight into the mechanism, showing the fluxional nature of gold(I)-stabilized vinyl carb...

Benzyne is shown to add elemental sulfur and give rise to a series of polysulfane compounds. A computational and experimental study is presented. Odd-membered o-C6H4Sx rings (x = 1-8), except x = 1, which suffers from ring strain, have enhanced stability compared to even-membered rings. The acquisition of "odd-even" data may shed new light, revealing patterns on polysulfane stability and struct...

The gold(I)-catalyzed intramolecular reaction of allenes with oxoalkenes leads to bicyclo[6.3.0]undecane ring systems, although in the case of terminally disubstituted allenes, seven-membered rings are formed. The related intermolecular addition of aldehydes to allenenes also gives seven-membered rings.

The title steroid, C(29)H(44)O(7), is a new androgen derivative and a key inter-mediate for synthesizing novel anti-HIV steroid agents. There are four trans-fused rings in the structure. The three six-membered rings exhibit chair conformations, while the five-membered ring adopts an envelope conformation.