The natural diterpenoid kamebanin

Kamebanin, alternatively called rel‐(?)‐(1R,4R,8S,9R,10S,13S,16R)‐2,8,16‐tri­hydroxy‐5,5,9‐tri­methyl‐14‐methyl­enetetra­cyclo­[11.2.1.0^1,10.0^4,9]­hexadecan‐15‐one, C₂₀H₃₀O₄, is a natural diterpenoid which has cytotoxic and antibacterial activity. The mol­ecule is composed of three six‐membered rings, which all adopt chair conformations, and one five‐membered ring, which adopts an envelope conformation. The conjugated α‐­methyl­ene­cyclo­pentanone ring is the active part in the mol­ecule due to the ring strain. All three hydroxy groups serve as hydrogen‐bond donors and acceptors, forming a continuous two‐dimensional network.     

Stereochemistry of two new polyfunctionalized gem‐dihalo­cyclo­propanes

The two new gem‐dihalogeno­cyclo­propanes (1′S,3R)‐3‐(2′,2′‐di­chloro‐1′‐methyl­cyclo­propyl)‐6‐oxoheptanoic acid, C₁₁H₁₆­Cl₂O₃, (2), and (1′S,3R)‐3‐(2′,2′‐di­bromo‐1′‐methyl­cyclo­propyl)‐6‐oxoheptanoic acid, C₁₁H₁₆Br₂O₃, (3), are isostructural. Both present two stereogenic centers at C1′ and C3. The absolute configuration was determined by X‐ray methods. The cyclo­propyl rings are unsymmetrical, the shortest bond being distal with respect to the alkyl‐substituted C atom.     

[(1R,2R)‐1,2‐Di­amino­cyclo­hexane‐κ2N,N′](α‐di­imine‐κ2N,N′)­platinum(II) bis­(hexa­fluoro­phosphate), where α‐di­imine is 2,2′‐bi­pyridine and 1,10‐phen­anthroline

The title Pt^II complexes, viz. (2,2′‐bi­pyridine‐κ²N,N′)[(1R,2R)‐1,2‐di­amino­cyclo­hexane‐κ²N,N′]­platinum(II) bis­(hexa­fluoro­phosphate), [Pt(C₆H₁₄N₂)(C₁₀H₈N₂)](PF₆)₂, and [(1R,2R)‐1,2‐di­amino­cyclo­hexane‐κ²N,N′](1,10‐phenanthroline‐κ²N,N′)platinum(II) bis­(hexa­fluoro­phosphate), [Pt(C₆H₁₄N₂)(C₁₂H₈N₂)](PF₆)₂, containing an aromatic α‐di­imine and a non‐planar di­amino­cyclo­hexane, both form a ladder‐type structure, which is constructed via loose π–π stacking on the α‐di­imine ligands and hydrogen bonding between the cyclic amines and the counter‐anions. In the former compound, there are two independent complex cations, both of which have a twofold axis through the Pt atom.     

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.     

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.     

Hydrido‐sulfido‐bridged triangular Os3 cluster compounds with different phosphine ligand substitution patterns

In the course of our studies of trinuclear osmium cluster complexes with bridging sulfido and hydrido ligands, the new compounds Os₃(μ‐H)(μ‐SR)(CO)₉(PHCy₂) (Cy = cyclo­hexyl) with R = phenyl, (I) (nona­carbonyl‐1κ³C,2κ³C,3κ³C‐di­cyclo­hexyl­phosphine‐3κP‐μ‐hydrido‐1:2κ²H‐μ‐phenyl­thio‐1:2κ²S‐triangulo‐triosmium), [Os₃H(C₆H₅S)(C₁₂H₂₃P)(CO)₉], and R = naphthyl, (II) [nona­carbonyl‐1κ³C,2κ²C,3κ⁴C‐di­cyclo­hexyl­phosphine‐2κP‐μ‐hydrido‐1:2κ²H‐μ‐(2‐naphthyl­thio)‐1:2κ²S‐triangulo‐triosmium], [Os₃H(C₁₀H₇S)(C₁₂H₂₃P)(CO)₉], were prepared. We report on these two phosphine‐substituted complexes, which exhibit perceptible changes of the Os—Os bond parameters due to the ligand‐substitution pattern.     

Three ginkgolide hydrates from Ginkgo biloba L.: ginkgolide A monohydrate,ginkgolide C sesquihydrate and ginkgolide J dihydrate,all determined at 120 K

A low‐temperature structure of ginkgolide A monohydrate, (1R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐dimethylethyl)‐hexa­hydro‐4,7b‐di­hydroxy‐8‐methyl‐9H‐1,7a‐epoxymethano‐1H,6aH‐cyclo­penta­[c]­furo­[2,3‐b]­furo­[3′,2′:3,4]­cyclopenta­[1,2‐d]­furan‐5,9,12(4H)‐trione monohydrate, C₂₀H₂₄O₉·H₂O, obtained from Mo Kα data, is a factor of three more precise than the previous room‐temperature determination. A refinement of the ginkgolide A monohydrate structure with Cu Kα data has allowed the assignment of the absolute configuration of the series of compounds. Ginkgolide C sesquihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11S,11aR)‐3‐(1,1‐di­methyl­ethyl)‐hexa­hydro‐2,4,7b,11‐tetrahydroxy‐8‐methyl‐9H‐1,7a‐epoxy­methano‐1H,6aH‐cyclopenta­[c]­furo­[2,3‐b]­furo­[3′,2′:3,4]­cyclo­penta­[1,2‐d]­furan‐5,9,12(4H)‐trione sesquihydrate, C₂₀H₂₄O₁₁·1.5H₂O, has two independent diterpene mol­ecules, both of which exhibit intramolecular hydrogen bonding between OH groups. Ginkgolide J dihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐di­methyl­ethyl)‐hexa­hydro‐2,4,7b‐tri­hydroxy‐8‐methyl‐9H‐1,7a‐epoxy­methano‐1H,6aH‐cyclo­penta­[c]­furo­[2,3‐b]furo[3′,2′:3,4]­cyclo­penta­[1,2‐d]­furan‐5,9,12(4H)‐trione dihydrate, C₂₀H₂₄O₁₀·2H₂O, has the same basic skeleton as the other ginkgolides, with its three OH groups having the same configurations as those in ginkgolide C. The conformations of the six five‐membered rings are quite similar across ­ginkgolides A–C and J, except for the A and F rings of ginkgolide A.     

(1R,3S)‐1‐Mono­amido­camphoric acid

The title compound, (1S,3R)‐3‐carbamoyl‐2,2,3‐tri­methyl­cyclo­pentane‐1‐carboxyl­ic acid, C₁₀H₁₇NO₃, was synthesized and characterized by IR, EA, ES–MS (electrospray ionization mass spectra), ¹H NMR, ¹³C NMR and X‐ray diffraction techniques. The two independent mol­ecules form a two‐dimensional network via O—H⃛O and N—H⃛O hydrogen‐bonding interactions between their carbox­ylic acid and carbamoyl groups.     

(1R,8R,11R)‐3,3,11‐Tri­methyl‐6,6‐ethyl­ene­dioxy­bi­cyclo­[6.3.0]­undecan‐2‐one and (1R,2R,8R,11R)‐3,3,11‐tri­methyl‐6,6‐ethylenedioxybicyclo[6.3.0]undecan‐2‐ol

The reduction of (1R,8R,11R)‐3,3,11‐tri­methyl‐6,6‐ethyl­ene­dioxy­bi­cyclo­[6.3.0]­undecan‐2‐one, C₁₆H₂₆O₃, (I), gave exclusively an alcohol, C₁₆H₂₈O₃, (II). The stereochemistry of the hydroxyl group in (II) was shown as R. The conformation around the eight‐membered carbocycle in (I) differs markedly from that in (II).     

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.     

An intermediate in a new synthesis approach to β‐substituted β‐hydroxy­aspartame

The crystal and molecular structure of 1‐tert‐butyl 4‐ethyl (2′R,3′R,5′R,2S,3S)‐3‐bromo­methyl‐3‐hydroxy‐2‐[(2′‐hydroxy‐2′,6′,6′‐tri­methyl­bi­cyclo­[3.1.1]­hept‐3′‐yl­idene)­amino]­succinate, C₂₁H₃₄BrNO₆, is presented. This compound is an intermediate in the new synthetic route to β‐substituted β‐hydroxy­aspartates, which are blockers of glutamate transport.     

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.     

(1R,3S)‐Camphoramic acid

The title chiral compound, 3‐amino­carbonyl‐1,2,2‐tri­methyl­cyclo­pentane‐1‐carboxylic acid, C₁₀H₁₇NO₃, was prepared from (1R,3S)‐camphoric acid. The five‐membered ring adopts a conformation which is intermediate between a twist and an envelope. Elongations of the C—C bonds and contractions of the C—C—C bond angles are observed within the five‐membered ring. A ¹H NMR spectrum was recorded to assist in distinguishing the amide group from the carboxyl group.     

(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.     

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.     

Precursor of a β‐lactamase inhibitor: allyl (4S,8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.03,8]­undec‐2‐ene‐2‐carboxyl­ate

The molecular structure of the title tricyclic compound, C₁₇H₂₁NO₄, which is the immediate precursor of a potent synthetic inhibitor {Lek157: sodium (8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.0^3,8]­undec‐2‐ene‐2‐carboxyl­ate} with remarkable potency, provides experimental evidence for the previously modelled relative position of the fused cyclo­hexyl ring and the carbonyl group of the β‐lactam ring, which takes part in the formation of the initial tetrahedral acyl–enzyme complex. In this hydro­phobic mol­ecule, the overall geometry is influenced by C—H?O intramolecular hydrogen bonds [3.046 (4) and 3.538 (6) Å, with corresponding normalized H?O distances of 2.30 and 2.46 Å], whereas the mol­ecules are interconnected through intermolecular C—H?O hydrogen bonds [3.335 (4)–3.575 (5) Å].     

Dibothrioclinin I and II,epimers from Gerbera piloselloides (L.) Cass

Dibothrioclinin I and II, namely (+)‐(11R,12S,25R,27S)‐ and (±)‐­(11RS,12RS,25RS,27SR)‐3,3,7,17,21‐penta­methyl‐4,12,18,26‐tetraoxahepta­cyclo­[15.11.1.0^2,15.0^5,14.0^6,11.0^19,28.0^20,25]­nona­cosa‐5(14),6,8,10,19(28),20,22,24‐octaene‐13,27‐dione, respectively, are C₃₀H₂₈O₆ epimers which are derived from two bothrioclinin moieties joined so as to create an additional six‐membered ring. Structurally, the epimers differ only by inversion at one C atom of a central ring junction and the corresponding six‐membered rings have similar conformations in each mol­ecule, except for one ring adjacent to this inversion site.     

Two 2,2‐dihalo‐N‐(1‐phenyl­ethyl)­cyclo­propane‐1‐carbox­amides

The crystal structures of (1R,1′S)‐2′,2′‐di­chloro‐N‐(1‐phenyl­ethyl)­cyclo­propane‐1′‐carbox­amide, C₁₂H₁₃Cl₂NO, (I), and (1R,1′R)‐2′,2′‐di­fluoro‐N‐(1‐phenyl­ethyl)­cyclo­propane‐1′‐car­box­amide, C₁₂H₁₃F₂NO, (II), have been determined. Both crystals contain two independent mol­ecules with different conformations of the phenyl­ethyl groups. In the crystals of both compounds, the mol­ecules are linked together by N—H⃛O hydrogen bonds, thus forming chains in the a direction.     

2,4‐Diamino‐5‐(1‐naphthyl)‐3,5‐diaza‐1‐azoniaspiro[5.5]undeca‐1,3‐diene chloride

The title salt, C₁₈H₂₂N₅⁺·Cl^?, is a member of a new series of lipophilic 4,6‐di­amino spiro‐s‐triazines which are potent in­hib­itors of di­hydro­folate reductase. The protonated triazine ring deviates from planarity, whereas the cyclo­hexane ring adopts a chair conformation. A rather unusual hydrogen‐bonding scheme exists in the crystal. There is a centrosymmetric arrangement involving two amino groups and two triazine ring N atoms, with graph‐set R(8) and an N?N distance of 3.098 (3) Å, flanked by two additional R(8) systems, involving two amino groups, a triazine ring N atom and a Cl^? anion, with N?Cl distances in the range 3.179 (2)–3.278 (2) Å. Furthermore, the Cl^? anion, the protonated triazine ring N atom and an amino group form a hydrogen‐bonding system with graph‐set R(6).     

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.