(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.     

X‐ray investigations of bicyclic α‐methyl­ene‐δ‐valerolactones. II. (4aS,8aS)‐4a‐Methyl‐3‐methyl­eneper­hydro­chromen‐2‐one

The title compound, C₁₁H₁₆O₂, adopts a semifolded conformation with the δ‐lactone and cyclo­hexane rings almost perpendicular to one another. The β‐methyl substituent occupies an axial position with respect to the cyclo­hexane ring. The δ‐lactone moiety adopts a slightly distorted half‐chair arrangement, while the cyclo­hexane ring exists in an almost ideal chair conformation.     

X‐ray investigations of bicyclic α‐methyl­ene‐δ‐valerolactones. III. trans‐(4aR,8aR)‐4a‐Methoxy‐3‐methyleneperhydro­chromen‐2‐one

The title compound, C₁₁H₁₆O₃, adopts a conformation in which the δ‐valerolactone and cyclo­hexane rings are almost coplanar with one another. The β‐methoxy substituent occupies an axial position with respect to the cyclo­hexane ring. The δ‐valerolactone moiety adopts a half‐chair arrangement, while the cyclo­hexane ring exists in a chair conformation.     

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.     

1,6‐Anhydro‐2,3‐di‐O‐benzyl‐5C‐[(R)‐ethoxycarbonyl(hydroxy)methyl]‐β‐l‐altrofuranose

The crystal structure of the title compound, C₂₄H₂₈O₈, has been determined. The conformation of the furan­ose ring can be described as 58% ideal envelope ^OE conformer and 42% ideal twisted ^OT₁ conformer. The 1,3‐dioxane ring adopts a chair conformation with the anhydro‐O atom pointing upwards. Both phenyl rings are quasi‐perpendicular to the mean plane of the furan­ose ring. The hydrogen bonding is intermolecular and consists of infinite chains parallel to the a axis.     

Two intermediates in the synthesis of deca­hydro­iso­quinolines with NMDA and AMPA receptor antagonist activity

In 6‐methyl‐N‐(4‐nitro­benzoyl)‐5,6‐di­hydropyridin‐2(1H)‐one, C₁₃H₁₂N₂O₄, (I), the piperidone ring is in a distorted half‐chair conformation. In 8‐methoxy‐3‐methyl‐N‐(4‐nitro­benzoyl)‐1,2,3,4,5,6,7,8‐octa­hydro­iso­quinoline‐1,6‐dione, C₁₈H₂₀N₂O₆, (II), the heterocyclic ring is in a slightly distorted half‐boat conformation, while the other six‐membered ring is in a distorted chair conformation. Compound (II) presents a strong intramolecular C—H?O hydrogen bond. In both (I) and (II), the mol­ecules interact through C—H?O interactions.     

A comparison of the ring conformational properties of two derivatives prepared from the same diene ­diacetate precursor

Results of single‐crystal X‐ray experiments performed for the title compounds, (1S,2R,3S,4R,5R)‐4‐benzyl­oxy‐2‐[1‐(benzyl­oxy)­allyl]‐5‐hydroxy­methyl‐2,3,4,5‐tetra­hydro­furan‐3‐ol, C₂₂H₂₆O₅, (I), and (3R,5S,6S,7S,8S)‐3,6‐bis­(benzyl­oxy)‐5‐iodo­methyl‐2,3,4,5‐tetra­hydro­furo­[3,2‐b]­furan‐2‐one, C₂₁H₂₁IO₅, (II), demonstrate that the tetra­hydro­furan ring that is common to both structures adopts a different conformation in each mol­ecule. Structural analyses of (I) and (II), which were prepared from the same precursor, indicate that their different conformations are caused by hydrogen‐bonding interactions in the case of (I) and the presence of a fused bicyclic ring system in the case of (II). Density functional theory calculations on simplified analogs of (I) and (II) are also presented.     

7,7‐Di­chloro‐1,6‐di­methyl‐2‐oxa‐5‐thia­bi­cyclo­[4.1.0]­heptane 5,5‐dioxide and 6‐chloro‐2,3‐di­hydro‐7‐methyl‐5‐methyl­ene‐2H,3H,5H‐1,4‐dithiepine 1,1,4,4‐tetraoxide

The structures of a 2‐oxa‐5‐thia­bi­cyclo­[4.1.0]­heptane derivative, C₇H₁₀Cl₂O₃S, (I), and a 2H,3H,5H‐1,4‐dithiepine derivative, C₇H₉ClO₄S₂, (II), are reported. The six‐membered ring in (I) has an envelope conformation and the seven‐membered ring in (II) adopts a chair conformation. There are no untoward intermolecular interactions in (I), but two Cl atoms make a short intermolecular contact across an inversion centre in (II), with a Cl?Cl distance of 3.2784 (9) Å, some 0.22 Å less than the sum of the van der Waals radii.     

2,5‐O‐Methyl­ene‐d‐mannitol: two polymorphs and the NaI complex

Two polymorphs of the title compound, (4R,5R,6R,7R)‐4,7‐bis­(hydroxy­methyl)‐1,3‐dioxepane‐5,6‐diol, C₇H₁₄O₆, both have Z′ = 2 at 100 K, and differ in their hydrogen‐bonding patterns. The sodium iodide complex, NaI·C₇H₁₄O₆, is isomorphous with the NaCl complex, and has the mannitol, cation and anion all lying on twofold axes. The dioxepane rings of all three mol­ecules are in the twist‐chair conformation.     

N1,N1-Diethyl-N2-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)acet­amidine

The solid-state conformation of the title compound, C₂₀H₃₂N₂O₉, has been determined at 150 K. The pyran­ose ring has a distorted chair conformation. Among the possible conformations of the C—N glycosidic bond, that of the E rotamer is observed and a short intramolecular C_methyl⋯O contact may partly stabilize this conformation. Crystal cohesion is stabilized by an extensive network of weak C—H⋯O hydrogen bonds and close contacts.     

(1R,2R)‐1,2‐Di­phenyl‐1,2‐bis(8‐quinoline­sulfonyl­amino)ethyl­enedi­amine–acetone (1/1)

The crystal structure of the new chiral complex (1R,2R)‐1,2‐di­phenyl‐1,2‐bis(8‐quinoline­sulfonyl­amino)‐ ethyl­enedi­amine–acetone (1/1), C₃₂H₂₆N₄O₄S₂^.C₃H₆O, is reported. The conformation of the C₃₂H₂₆N₄O₄S₂ (BQSDA) mol­ecule is determined by a bifurcated N—H?N hydrogen‐bond system. The acetone of solvation is linked to the BQSDA mol­ecule by an N—H?O hydrogen bond.     

Triterpenoide. XIX. 3β‐Hydroxy‐11‐oxo‐18α‐olean‐12‐en‐28‐säure‐methyl­ester und 3,11‐Dioxo‐18α‐olean‐12‐en‐28‐säure‐methyl­ester

The X‐ray crystal structure analyses of 3β‐hydroxy‐11‐oxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester ethanol solvate, C₃₁H₄₈O₄·C₂H₆O, (I), and 3,11‐dioxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester, C₃₁H₄₆O₄, (II), are described. These two compounds differ only in the structure of ring A. In (I), ring A has a chair conformation, while in (II), it has a twisted boat conformation. In both compounds, ring C has a slightly distorted sofa conformation, rings B, D and E are in chair conformations, and rings D and E are trans‐fused. The asymmetric unit of (I) contains one mol­ecule of ethanol linked by hydrogen bonds with two different mol­ecules of (I).     

The fungal metabolite austdiol

The title compound, (7R,8S)‐7,8‐di­hydroxy‐3,7‐di­methyl‐6‐oxo‐7,8‐di­hydro‐6H‐isochromene‐5‐carb­aldehyde, C₁₂H₁₂O₅, is a trans‐vicinal diol. Of the two fused rings, which lie approximately in the same plane, the pyran ring is almost perfectly planar, while the cyclo­hexenone ring adopts a slightly distorted half‐chair conformation. The crystal packing is dictated by two strong intermolecular O—H⃛O interactions, one involving hydroxy and keto groups, the other involving two hydroxy groups. Molecules are linked together through twofold axes, forming zigzag ribbons extended along the a axis.     

cis,cis,cis‐1,2,4,5‐Cyclo­hexane­tetra­carboxyl­ic acid and its dianhydride

cis,cis,cis‐1,2,4,5‐Cyclo­hexane­tetra­carboxyl­ic acid, C₁₀H₁₂O₈, (I), contains a mirror plane and the cyclo­hexane ring exhibits a chair conformation. Two crystallographically independent hydrogen bonds form (14), (16) and (16) ring motifs, and propagation of these two hydrogen bonds along the c and b axes generates (16) and (7) chains. cis,cis,cis‐1,2:4,5‐Cyclo­hexane­tetra­carboxyl­ic dianhydride, C₁₀H₈O₆, (II), was prepared by the reaction of (I) with acetic anhydride. The cyclo­hexane ring of (II) exhibits a boat conformation and the dihedral angle between the two an­hydro rings is 117.5 (1)°.     

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.     

3β‐(1‐Allyl‐1‐pyrrolidinio)‐16‐(2‐pyridylmethylene)androst‐5‐en‐17β‐ol bromide hemihydrate

The title compound, C₃₂H₄₅N₂O⁺·Br^?·0.5H₂O, has the outer two six‐membered rings in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐mem­bered ring of the steroid nucleus adopts a slightly deformed 14α‐envelope conformation. The pyridyl­methyl­ene moiety has an E configuration with respect to the hydroxyl group at position 17. The structure is stabilized by a network of O—H?Br‐type intermolecular hydrogen bonds.     

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.     

6‐Deoxy­jacareubin

The natural compound 5,10‐di­hydroxy‐2,2‐di­methylpyrano­[3,2‐b]­xanthen‐6(2H)‐one (6‐deoxy­jacareubin), C₁₈H₁₄O₅, was isolated from leaves of Vismia latifolia (Guttiferae family). The compound has four six‐membered rings. The mol­ecule has two planar benzeno­id and one planar pyran­oid ring, plus a pyran­oid ring in a distorted chair conformation. The crystal is stabilized by one intra‐ and one intermolecular hydrogen bond.     

A semi‐synthetic analog of the cembranoid sarcophine

The title mol­ecule, 2(R)‐[(1E,3E,7S,8S,11E,13R)‐13‐hydroxy‐4,8,12‐tri­methyl‐7,8‐epoxy­cyclo­tetradeca‐1,3,11‐trien‐1‐yl]­propane‐1,2‐diol, C₂₀H₃₂O₄, is a semi‐synthetic analog of sarcophine, the natural cembranoid of marine origin, isolated from the soft coral Sarcophyton glaucum. The conformation of the 14‐membered ring differs substantially from that of sarcophine. The two OH groups of the propane‐1,2‐diol moiety form an unusual weak intramolecular hydrogen bond with an O⋯O distance of 2.788 (2) Å, and the mol­ecules are linked into double chains by intermolecular hydrogen bonds with O⋯O distances of 2.772 (2) and 2.849 (2) Å.