Precursors to dodecahedrane

The title compounds, (2R,2′′S,3b′S,4a′R,7b′S,8a′R)‐per­hydro­di­spiro­[furan‐2,3′‐di­cyclo­penta­[a,e]­pentalene‐7′,2′′‐furan]‐5,5′′‐dione, C₂₀H₂₆O₄, and (3aR,3bR,4aR,4bS,5aS,8aR,8bR,9aR,9bS,10aS)‐per­hydro­dipentaleno­[2,1‐a:2′,1′‐e]­pentalene‐1,6‐dione, C₂₀H₂₆O₂, are intermediates identified during the synthesis of dodecahedrane. Crystallographic studies have established the ring‐junction stereochemistry for these important intermediates. All the ring junctions are cis‐fused, and the molecular packing is stabilized by van der Waals interactions.     

Diels–Alder adducts of maleic ­anhydride and dienes: new compounds by crystallization

We have determined the crystal structures of bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic anhydride, C₉H₈O₃, (I), 1,2,3,4,7,7‐hexa­chloro­bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic anhydride diethyl ether solvate, C₉H₂Cl₆O₃·0.16­C₄H₁₀O, (II), bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic acid, C₉H₁₀O₄, (III), 1,2,3,4,7,7‐hexa­chloro­bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic acid, C₉H₄Cl₆O₄, (IVa) and (IVb), and ethyl 1,2,3,4,7,7‐hexa­chloro‐6‐carboxybi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5‐carboxyl­ate monohydrate, C₁₁H₈Cl₆O₄·H₂O, (V). Compounds (I) and (II) were prepared by a standard Diels–Alder reaction from maleic anhydride and cyclo­penta­diene or hexa­chloro­cyclo­penta­diene, respectively. The crystal‐growing processes of these compounds led to surprising results: rapid recrystallization of (I) from diethyl ether and (II) from petroleum ether gave crystals of these compounds, however, crystallization by slow evaporation techniques using common solvents yielded new compounds in which the five‐membered heterocycle has been cleaved.     

Samaderin B and C from Samadera indica

Samaderin B, or (1R,2S,5R,5aR,7aS,11S,11aS,11bR,14S)‐1,7,7a,11,11a,11b‐hexa­hydro‐1,11‐di­hydroxy‐8,11a,14‐tri­methyl‐2H‐5a,2,5‐(methan­oxy­metheno)­naphth­[1,2‐d]­oxepine‐4,6,10(5H)‐trione, C₁₉H₂₂O₇, and samaderin C, or (1R,2S,5R,5aR,7aS,10S,11S,11aS,11bR,14S)‐7,7a,10,11,11a,11b‐hexa­hydro‐1,10,11‐tri­hydroxy‐8,11a,14‐tri­methyl‐2H‐5a,2,5‐(methan­oxy­metheno)­naphth­[1,2‐d]­oxepine‐4,6(1H,5H)‐dione, C₁₉H₂₄O₇, were isolated from the seed kernels of Samadera indica and were shown to exhibit antifeedant activity against Spodoptera litura third‐instar larvae. The replacement of the carbonyl group in samaderin B by a hydroxy group in samaderin C causes conformational changes at the substitution site, but the overall conformation is not affected; however, the compounds pack differently in the crystal lattice.     

2′,3′‐Dehydrosalannol

The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodeca­hydro‐3‐hydroxy‐2a,5a,6a,7‐tetra­methyl‐5‐(3‐methylbut‐2‐enoyl­oxy)‐2H,3H‐cyclo­penta­[4′,5′]­furo­[2′,3′:6,5]benzo[cd]­isobenzo­furan‐6‐acetate, C₃₂H₄₂O₈, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐des­acetyl­salannin, which was isolated from neem kernels. The mol­ecules are linked into chains by intermolecular O—H?O hydrogen bonds.     

Azadirachtol,a tetranortriterpenoid from neem kernels

The title compound, di­methyl (?)‐(2aR,3R,4R,4aS,5R,7aS,8R,10S,10aR)‐3,8,10‐tri­hydroxy‐4‐[(2R,6R)‐2‐hydroxy‐11‐methyl‐5,7,10‐trioxatetra­cyclo­[6.3.1.0^2,60^9,11]­dodec‐3‐en‐9‐yl]‐4‐methyl­per­hydro­isobenzo­furano­[5,4,3a‐cd]­isobenzofuran‐5,10a‐di­acetate, C₂₈H₃₆O₁₃, which exhibits higher antifeedant activity than azadirachtin‐A, a known potent antifeedant, was isolated from neem kernels. The asymmetric unit of the structure contains two independent mol­ecules, which differ in the conformations of their functional groups and also in the conformations of some of the rings. The relative orientation between the decalin and furan­yl moieties is similar to that observed in the majority of azadirachtin structures, but is different from that in azadirachtin‐A. The two symmetry‐independent mol­ecules are linked into dimeric units by intermolecular O—H?O hydrogen bonds.     

Preference for the Diels–Alder addition of dienes syn to the O atom in cross‐conjugated spiro­cyclic cyclo­hexadienones

In the Diels–Alder reaction, the preferred addition of dienes syn to the O atom in cross‐conjugated cyclo­hexadienones containing an oxa‐­spiro ring system is observed. The two structures reported here, namely rel‐(1R,4aR,9S,9aS,10R)‐4a,9,9a,10‐tetra­hydro‐9,10‐di­phenyl­spiro­[9,10‐epoxy­anthra­cene‐1(4H),2′‐oxiran]‐4‐one, C₂₇H₂₀O₃, and rel‐(1R,4aS,9R,9aS,10S)‐4a,9,9a,10‐tetra­hydro‐9,10‐di­phenyl­spiro­[9,10‐epoxy­anthracene‐1(4H),2′‐oxetane]‐4‐one, C₂₈H₂₂O₃, are the minor and sole products, respectively, of the reactions of di­phenyl­isobenzo­furan with two slightly different cyclo­hexadienones. These structures differ in the size of the oxa‐­spiro ring, by one C atom, and in the relative configuration at the spiro­cyclic ring C atom, leading to some minor conformational differences between the two compounds.     

Azido­[1,1′‐bis­(di­phenyl­phosphino)­ferrocene](penta­methyl­cyclo­penta­dienyl)­rhodium(III) hexa­fluoro­phosphate

In the title compound, azido‐2κN‐bis­[μ‐(1η⁵:2κP)‐di­phenyl­phosphino­cyclo­penta­dienyl][2(η⁵)‐penta­methyl­cyclo­penta­di­enyl]­iron(III)­rhodium(III) hexa­fluoro­phosphate, [{Rh(C₁₀H₁₅)(N₃)}{Fe(μ‐C₁₇H₁₄P)₂}]PF₆ or [FeRh(C₁₀H₁₅)(μ‐C₁₇H₁₄P)₂(N₃)]PF₆, the coordination sphere of Rh^III can be described as pseudo‐tetrahedral, composed of two P atoms from a 1,1′‐bis­(di­phenyl­phosphino)­ferrocene (dppf) ligand, an azido N atom and the centroid of the ring of a C₅Me₅ (Cp*) ligand. The two cyclo­penta­dienyl rings in the dppf moiety adopt an eclipsed conformation. The Rh⋯Fe distance is 4.340 (2) Å.     

(4R,4aR,6S,7S,7aS)‐6‐Hydro­xy‐7‐hy­droxy­methyl‐4‐methyl­per­hydro­cyclo­penta­[c]­pyran‐1‐one chloro­form solvate from Valeriana laxiflora

The structure of an iridolactone isolated from Valeriana laxiflora was established as (4R,4aR,6S,7S,7aS)‐6‐hydroxy‐7‐hydroxy­methyl‐4‐methyl­per­hydro­cyclo­penta­[c]­pyran‐1‐one chloro­form solvate, C₁₀H₁₆O₄·CHCl₃. The two rings are cis‐fused. The δ‐lactone ring adopts a slightly twisted half‐chair conformation with approximate planarity of the lactone group and the cyclo­pentane ring adopts an envelope conformation. The hydroxy group, the hydroxymethyl group and the methyl group all have β orientations. The absolute configuration was determined using anomalous dispersion data enhanced by the adventitious inclusion of a chloro­form solvent mol­ecule. Hydro­gen bonding, crystal packing and ring conformations are discussed in detail.     

Chiral and meso‐bis([2.2]­para­cyclo­phan‐4‐yl)­methane and meso‐bis­([2.2]­para­cyclo­phan‐4‐yl) sulfide

The [2.2]­para­cyclo­phane groups of the title compounds, chiral and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl)­methane (the former as a racemate), C₃₃H₃₂, and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl) sulfide, C₃₂H₃₀S, show the characteristic structural features of the parent compound [2.2]­para­cyclo­phane and the related compound di­methylbis([2.2]­para­cyclo­phan‐4‐yl)­silane, C₃₄­H₃₆­Si: the aromatic rings are puckered, resulting in a boat conformation. The planes of the four coplanar C atoms are slightly twisted with respect to each other. The Csp³—Csp³ bond lengths of the ethyl­ene bridges are elongated by the electronic and steric effects of the skeleton.     

Diels–Alder adducts of medium-ring carbocyclic dienes prepared by rearrangement of catalytically generated cyclic oxonium ylides

The novel bicyclic and tricyclic systems di­methyl (4aS*,6S*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexa­hydro-2H-benzo­cyclo­hept­ene-3,4-di­carboxyl­ate, C₁₆H₂₀O₆, (I), di­methyl (4aS*,6R*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexa­hydro-2H-benzo­cyclo­hept­ene-3,4-di­carboxyl­ate, C₁₆H₂₀O₆, (II), (3aS*,9R*,10aS*,10bR*)-9-methoxy-2-oxa-1,3a,4,6,7,8,9,10,10a,10b-deca­hydro-3H-cyclo­hepta­[e]­indene-1,3,8-trione, C₁₄H₁₆O₅, (III), and (1S*,2R*,9S*,10aR*)-9-methoxy-8-oxo-1,2,3,5,6,7,8,9,10,10a-deca­hydrobenzo­cyclo­octene-1,2-di­carboxyl­ic acid, C₁₅H₂₀O₆, (IV), have been crystallographically characterized, allowing the determination of the relative configuration of the stereogenic centres. The poor quality of the di­carboxyl­ic acid crystals necessitated the use of synchrotron radiation.     

Rotenone α‐oxime

The structure determination of the title compound, rotenone α‐oxime [systematic name: 1,2,12,12a‐tetra­hydro‐8,9‐di­meth­oxy‐2‐(1‐methyl­ethenyl)‐[1]­benzo­py­rano­[3,4‐b]­furo­[2,3‐h][1]benzo­pyran‐6(6H)‐one oxime], C₂₃H₂₃NO₆, confirms that the mol­ecule has an approximately V‐shaped structure. One of the rings has a typical cyclo­hexene‐like monoplanar conformation and the central ring adopts a 1,2‐diplanar conformation.     

A `tetrameric' 3,4‐di‐p‐tolyl‐1,2,5‐oxadiborole derivative

In the title compound, 1,1,6a,7,9a,10‐hexa­chloro‐2,3,5,6,8,9,11,12‐octa‐p‐tolyl‐1,6a,9a,12a‐tetraborata‐3a,4a,7,10‐tetrabora‐4a¹,6b,9b,12b‐tetraoxonia‐4‐oxatetra­cyclo­penta­[1,2‐a:2,1,5‐de:1,2‐g:1,2‐i]­naphthalene di­chloro­methane pentasolvate, C₆₄H₅₆B₈Cl₆O₅·5CH₂Cl₂, two condensed oxadiborole rings are attached to two further oxadiborole rings in a type of donor–acceptor bonding, thus forming a ten‐membered alternating (B—O)₅ naphthalene‐like arrangement as the central building block.     

Hamigerin A and a hamigerin D decomposition product

The sponge Hamigera tarangaensis has yielded eight new compounds and we report here the structure of one of these compounds, hamigeran A, C₂₀H₂₅BrO₅, or methyl 7‐bromo‐4β,6‐di­hydroxy‐1β‐iso­propyl‐3aα,8‐di­methyl‐5‐oxo‐1a,3a,4,5‐tetra­hydro­cyclo­penta­[a]­naphthalene‐4‐carboxyl­ate, and the decomposition product of hamigeran D, C₂₁H₂₈BrNO₄, namely 2‐(8‐bromo‐2β,7‐di­methyl‐4‐oxo‐1,3α‐benzox­aza­n‐5‐yl)‐3‐iso­propylcyclo­pentyl­acetic acid.     

A spiro‐linked pyrene–naphtho­quinone

The title mol­ecule, 2′‐pyrenyl­spiro­[2,3‐di­hydro‐1H‐cyclo­penta­[b]­naphthalene‐2,5′‐1′,3′‐dioxane]‐4,9‐dione, C₃₂H₂₂O₄, contains an electron‐donating pyrene group spiro‐linked to an electron‐accepting naphtho­quinone. The mol­ecules are V‐shaped in profile and stack to form columns along b with alternating, approximately coplanar, pyrene and naphtho­quinone fragments. Intermolecular contacts within a column are consistent with some degree of π contact and possible long‐range delocalization. Individual columns form a herringbone pattern when the crystal is viewed along b .     

Mikanolide from Jamaican Mikania micrantha

Mikanolide [systematic names: 1,10:2,3‐di­epoxy‐6,8‐di­hy­droxy‐11‐vinyl­germacr‐4‐ene 12,14‐di‐γ‐lactone and 7,10a‐di­methyl‐1a,1b,2a,6a,7,9a,10,10a‐octa­hydro‐4H‐6,3‐metheno­furo­[3,2‐c]­bisoxireno­[f,h]­oxa­cyclo­undecin‐4,8(6H)‐dione], C₁₅H₁₄O₆, derived from a variety of Mikania micrantha growing in Portland, Jamaica, contains a methyl­cyclo­decane ring fused to an unsaturated planar α,γ‐lactone, an envelope‐type near‐planar vinyl‐β,γ‐lactone and two epoxide moieties. The crystal packing shows stacks of mikanolide mol­ecules interlocked via a network of non‐classical C—H⋯O hydrogen bonds between the lactone units.     

Simvastatin

Simvastatin, or (1S,3R,7S,8S,8aR)‐8‐{2‐[(2R,4R)‐4‐hydroxy‐6‐oxo‐3,4,5,6‐tetra­hydro‐2H‐pyran‐2‐yl]­ethyl}‐3,7‐di­methyl‐1,2,3,7,8,8a‐hexa­hydro­naphthalen‐1‐yl 2,2‐di­methyl­butan­oate, C₂₅H₃₈O₅, is almost isostructural with lovastatin, and the general conformational features are closely related to those of other reported crystal structures of statins. The only hydrogen bond present facilitates the formation of infinite chains of mol­ecules along the b axis.     

A pair of epimeric 13‐hydroxy‐2,3,6,7‐tetra­methoxy‐8b,11,12,12a,13,13a‐hexa­hydro‐9H‐9a‐aza­cyclo­penta­[b]tri­phenyl­ene‐10‐ones

The structures of two compounds which are intermediates in the synthesis of phenanthroindolizidine alkaloids have been determined. (8bS,13aS,14R,14aR)‐8b,9,11,12,13,13a,14,14a‐Octa­hydro‐14‐hydroxy‐2,3,6,7‐tetra­methoxy­dibenzo­[f,h]pyrrolo[1,2‐b]­isoquinolin‐11‐one acetone solvate, C₂₄H₂₇NO₆·C₃H₆O, (II), crystallizes in a chiral space group with one solvent mol­ecule (acetone) present in the asymmetric unit. On the other hand, (8bS,13aS,14S,14aR)‐8b,9,11,12,13,13a,14,14a‐octa­hydro‐14‐hydroxy‐2,3,6,7‐tetra­methoxy­dibenzo­[f,h]pyrrolo[1,2‐b]­isoquinolin‐11‐one, C₂₄H₂₇NO₆, (III), crystallizes in a centrosymmetric space group with two mol­ecules in the asymmetric unit and with no solvent present. The two mol­ecules in the asymmetric unit of (III) are structurally the same. Compounds (II) and (III) are epimers at the C atom carrying the OH group; otherwise they are very similar in structure.     

An anthracene dimer with a fused 1,3‐dithiole ring at 193 K

The first butterfly‐shaped anthracene dimer including S atoms,8,9‐di­hydro‐3a,8[1′,2′]:9,13b[1′′,2′′]­di­benzeno­dibenzo­[3,4:7,8]cyclo­octa­[1,2‐d]‐1,3‐di­thiole, C₂₉H₂₀S₂, contains an exceptionally long Csp³—Csp³ bond of 1.672 (2) Å in the fused 1,3‐di­thiole ring. The length of the other bond bridging the anthracene moieties is 1.604 (3) Å.     

A fluoro­phenylboron‐functionalized zirconium silsesquioxane complex

Bis(η⁵‐cyclo­penta­dienyl)[rel‐(1R,5S,7R,14S)‐(1,3,5,7,9,11,14‐hepta­cyclo­pentyl‐7,14‐dioxidotri­cyclo­[7.3.3^1,9.1^5,11]­hepta­siloxan‐3‐yloxy)­bis­(penta­fluoro­phenyl)­borane(2−)]­zirconium, [Zr(C₅H₅)₂(C₄₇H₆₃BF₁₀O₁₂Si₇)], consists of [ZrCp₂] (Cp is cyclopentadienyl) and [(C₆F₅)₂B] moieties bound to a silsesquioxane core. The silsesquioxane binds to the Zr atom through two of its O atoms to form a distorted tetrahedron. The [(C₆F₅)₂B] moiety is bound to the silsesquioxane through an O atom, forming an Si—O—B bond angle of 168.4 (4)°. The steric and electronic effects of the Zr atom and the borate moieties force the silsesquioxane core to distort. These distortions can be seen by examination of the Si—O—Si bond angles.     

An ion pair formed by protonated Fe(cp*py)2 and the octanuclear cluster U8Cl24O4(cp*py)2 [cp*py is tetramethyl‐5‐(2‐pyridyl)cyclopentadiene]

In bis­[1,1′,2,2′,3,3′,4,4′‐octa­methyl‐5‐(2‐pyridinio)‐5′‐(2‐pyri­dyl)­ferrocene] di‐μ₃‐chloro‐hexadeca‐μ₂‐chloro‐hexa­chloro­di‐μ₄‐oxo‐di‐μ₃‐oxo‐bis­[(η⁵,κN)‐1,2,3,4‐tetra­methyl‐5‐(2‐pyridyl)­cyclo­penta­dienyl]octauranium(IV) di­chloro­methane tetrasolvate, [Fe(C₁₄H₁₇N)(C₁₄H₁₆N)]₂[U₈Cl₂₄O₄(C₁₄H₁₆N)₂]·4CH₂Cl₂, (I), two protonated Fe(cp*py)₂ units [cp*py is tetra­methyl‐5‐(2‐pyridyl)­cyclo­penta­diene] form an ion pair with the dianionic centrosymmetric cluster U₈Cl₂₄O₄(cp*py)₂. The latter is the highest nuclearity assemblage in the chemistry of uranium (non‐uranyl) compounds reported to date.