(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.     

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.     

(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.     

Bergenin monohydrate from the rhizomae of Astilbe chinensis

The title compound, 4‐methoxy‐2‐[(1S,2R,3S,4S,5R)‐3,4,5,6‐tetrahydro‐3,4,5‐tri­hydroxy‐6‐(hydroxy­methyl)‐2H‐­pyran‐2‐yl]‐α‐resorcylic acid δ‐lactone monohydrate, C₁₄H₁₆O₉·H₂O, is a C‐glucoside of 4‐O‐methylgallic acid which has antiasthmatic, antitussive, anti‐inflammatory, antifungal, anti‐HIV and antihepatotoxic activity. The mol­ecule is composed of three six‐membered rings: an aromatic ring, a glucopyran­ose ring and an annellated δ‐lactone ring. The glucopyran­ose ring exhibits only small deviations from an ideal chair conformation. The annellated δ‐lactone ring possesses the expected half‐chair conformation. There is one intra‐ and six intermolecular hydrogen bonds which form an extensive hydrogen‐bonding network within the crystal.     

The 1:1 adduct of Kemp's triacid with 2‐aminopyridine

The crystal structure determination of the molecular proton‐transfer adduct of Kemp's triacid (cis‐cis‐1,3,5‐tri­methyl­cyclo­hexane‐1,3,5‐tri­carboxylic acid, KTA) with 2‐amino­pyridine (2‐APY), namely 2‐amino­pyridinium 3,5‐di­carboxy‐1,3,5‐tri­methyl­cyclo­hexane­carboxyl­ate, 2‐APY⁺·KTA^? or C₅H₇N₂⁺·C₁₂H₁₇O₆^?, has revealed a centrosymmetric hydrogen‐bonded cyclic KTA homodimer repeating unit [O?O 2.524 (4) Å] linked into a polymer structure through the pyridinium and amino groups of the 2‐APY mol­ecule [O?N 2.736 (4), 2.989 (4) and 2.999 (4) 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.     

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.     

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].     

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.     

Packing considerations of bis‐dimedone derivatives

We have determined the crystal structures of 2,2′‐(4‐fluoro­phenyl)­methyl­enebis(3‐hydroxy‐5,5‐di­methyl‐2‐cyclo­hexen‐1‐one), C₂₃H₂₇FO₄, (I), 2,2′‐(4‐chloro­phenyl)­methyl­enebis(3‐hy­droxy‐5,5‐dimethyl‐2‐cyclo­hexen‐1‐one), C₂₃H₂₇ClO₄, (II), 2,2′‐(4‐hydroxy­phenyl)­methyl­enebis(3‐hydroxy‐5,5‐di­methyl‐2‐cyclo­hexen‐1‐one), C₂₃H₂₈O₅, (III), 2,2′‐(4‐methyl­phenyl)­methyl­enebis(3‐hydroxy‐5,5‐di­methyl‐2‐cyclo­hexen‐1‐one), C₂₄H₃₀O₄, (IV), 2,2′‐(4‐methoxy­phenyl)­methyl­enebis(3‐hy­droxy‐5,5‐di­methyl‐2‐cyclo­hexen‐1‐one), C₂₄H₃₀O₅, (V), and 2,2′‐(4‐N,N′‐di­methyl­amino­phenyl)­methyl­enebis(3‐hydroxy‐5,5‐di­methyl‐2‐cyclo­hexen‐1‐one), C₂₅H₃₃NO₄, (VI). Structures (III) to (VI) of these bis‐dimedone derivatives show nearly the same packing pattern irrespective of the different substituent in the para position of the aromatic ring. However, (II) does not fit into this scheme, although the Cl atom is a substituent not too different from the others. The different packing of the fluoro compound, (I), can be explained by the fact that it crystallizes with two mol­ecules in the asymmetric unit, which show a different conformation of the dimedone ring. On the other hand, (I) shows a similar packing pattern to bis(2‐hydroxy‐4,4‐di­methyl‐6‐oxo‐1‐cyclo­hexenyl)­phenyl­methane, a compound containing an aromatic ring without any substituent and with Z′ = 2.     

Macrocalyxin I

The title compound, 2‐[1,2,3,4,4a,4b,5,6,7,8,8a,9‐dodeca­hydro‐7‐hydroxy‐4b,8,8‐tri­methyl­phenanthren‐2‐yl]­propenoic acid, C₂₀H₃₀O₃, is a naturally occurring diterpenoid which was isolated from Rabdosia macrocalyx. The hydroxy and carboxy groups, which are located at the two ends of the mol­ecule, both serve as simultaneous hydrogen‐bond donors and acceptors. Two intermolecular O—H?O hydrogen bonds are present and link each mol­ecule to four neighbours, thus forming an extensive hydrogen‐bond network within the crystal.     

Moxifloxacinium chloride–water–methanol (2/1/1), a novel anti­bacterial agent

Moxifloxacin, a novel fluoro­quinolone with a broad spectrum of anti­bacterial activity, is available as the solvated monohydro­chloride salt 7‐[(S,S)‐2‐aza‐8‐azoniabicyclo­[4.3.0]non‐8‐yl]‐1‐cyclo­propyl‐6‐fluoro‐8‐meth­oxy‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylic acid chloride–water–methanol (2/1/1), C₂₁H₂₅FN₃O₄⁺·Cl⁻·0.5H₂O·0.5CH₃OH. The asymmetric unit contains two cations, two chloride ions, a mol­ecule of water and one methanol mol­ecule. The two cations adopt conformations that differ by an almost 180° rotation with respect to the piperidinopyrrolidine side chain. The cyclo­propyl ring and the meth­oxy group are not coplanar with the quinoline ring system. The carboxylic acid function, the protonated terminal piperidyl N atom, the water mol­ecule, the chloride ion and the methanol mol­ecule participate in O—H⋯O, O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonding, linking the mol­ecules into extended two‐dimensional networks.     

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.     

Tetracycline hydrochloride: a synchrotron microcrystal study

The title compound, [(4S,4aS,5aS,6S,12aS)‐2‐amino­hydroxy­methyl­ene‐1,2,3,4,4a,5,5a,6,11,12a‐deca­hydro‐6,10,12,12a‐tetra­­hydroxy‐6‐methyl‐1,3,11‐trioxo­naphthacen‐4‐yl]­di­methyl­amm­onium chloride, C₂₂H₂₅N₂O₈⁺·Cl^?, a well known antibiotic, has been structurally characterized from an individual coarse powder grain by use of high‐intensity synchrotron radiation, in conjunction with an exercise in ab initio powder diffraction structure solution. Free refinement of all H atoms establishes the major tautomeric form of the protonated tetracycline mol­ecule without prejudice. The mol­ecule has extensive intramolecular hydrogen bonding involving most of the potential donors and acceptors, and all intermolecular hydrogen bonding uses the chloride anion as acceptor.     

Absolute configuration and conformational disorder of a tricyclic thio­semicarbazone derivative

The title compound, (1S,3R,8R)‐2,2‐dichloro‐3,7,7,10‐tetra­methyl­tricyclo­[6.4.0.0^1,3]­dodecan‐11‐one thio­semicarbazone, C₁₇H₂₅Cl₂N₃S, has two disordered conformations of the cyclo­heptane moiety and a screw‐boat conformation for the cyclo­hexene ring. The absolute configuration was established.     

(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.     

Ranitidine hydro­chloride,a polymorphic crystal form

In the title compound, di­methyl­({5‐[2‐(1‐methyl­amino‐2‐nitro­eth­enyl­amino)­ethyl­thio­methyl]‐2‐furyl}­methyl)­ammon­ium chloride, C₁₃H₂₃N₄O₃S⁺·­Cl^?, protonation occurs at the di­methyl­amino N atom. The ranitidine mol­ecule adopts an eclipsed conformation. Bond lengths indicate extensive electron delocalization in the N,N′‐di­methyl‐2‐nitro‐1,1‐ethenedi­amine system of the mol­ecule. The nitro and methyl­amino groups are trans across the side chain C=C double bond, while the ethyl­amino and nitro groups are cis. The Cl^? ions link mol­ecules through hydrogen bonds.     

2‐{[Tris(hydroxymethyl)methyl]aminomethylene}cyclohexa‐3,5‐dien‐1(2H)‐one and its 6‐hydroxy and 6‐methoxy derivatives

The title compounds, 2‐{[tris­(hydroxy­methyl)­methyl]­amino­methyl­ene}cyclo­hexa‐3,5‐dien‐1(2H)‐one, C₁₁H₁₅NO₄, (I), 6‐hydroxy‐2‐{[tris­(hydroxy­methyl)­methyl]­amino­methyl­ene}­cyclo­hexa‐3,5‐dien‐1(2H)‐one, C₁₁H₁₅NO₅, (II), and 6‐methoxy‐2‐{[tris­(hydroxy­methyl)­methyl]­amino­methyl­ene}­cyclo­hexa‐3,5‐dien‐1(2H)‐one, C₁₂H₁₇NO₅, (III), adopt the keto–amine tautomeric form, with the formal hydroxy H atom located on the N atom, and the NH group and oxo O atom display a strong intramolecular N—H⋯O hydrogen bond. The N—H⋯O hydrogen‐bonded rings are almost planar and coupled with the cyclo­hexa­diene rings. The carbonyl O atoms accept two other H atoms from the alcohol groups of adjacent mol­ecules in (I), and one from the alcohol and one from the phenol group in (II), but from only one alcohol H atom in (III).     

Hexa­methyl­enetetra­mine–4‐nitro­catechol–water (1/2/1)

In the title adduct, 1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]dec­ane–4‐nitro­benzene‐1,2‐diol–water (1/2/1), C₆H₁₂N₄·2C₆H₅NO₄·H₂O, the hexa­methyl­ene­tetra­mine mol­ecule acts as an acceptor of intermolecular O—H?N hydrogen‐bonding interactions from the water mol­ecule and the hydroxy groups of one of the two symmetry‐independent 4‐nitro­catechol mol­ecules. The structure is built from molecular layers which are stabilized by three intermolecular O—H?O, two intermolecular O—H?N and four intermolecular C—H?O hydrogen bonds. The layers are further interconnected by one additional intermolecular O—H?N and two intermolecular C—H?O hydrogen bonds.     

Two (+)‐α,4‐dimethyl‐2‐oxocyclo­hexaneacetic acids: hydrogen bonding in a terpenoid γ‐keto acid and in a diastereomeric lactol

The (+)‐(αS,1S,4R)‐diastereomer of the title structure, C₁₀H₁₆O₃, aggregates in the solid as non‐symmetric dimers with disorder in both carboxyl groups [O·O = 2.710 (5) and 2.638 (5) Å]. The two mol­ecules constituting the asymmetric unit pair around a pseudo‐twofold rotational axis and differ only slightly in their distances and angles, but one methyl group displays rotational disorder absent in the other mol­ecule. Five inter­molecular C—H·O close contacts exist, involving both ketone groups. The (+)‐(αR,1R,4R)‐diastereomer exists in the crystal in its closed‐ring lactol form, (3R,3aR,6R,7aR)‐2,3,3a,4,5,6,7,7a‐octa­hydro‐7a‐hydroxy‐3,6‐dimethyl­benzo[b]furan‐2‐one, C₁₀H₁₆O₃, and aggregates as hydrogen‐bonded catemers that extend from the hydroxyl group of one mol­ecule to the carbonyl group of a neighbor screw‐related along b [O·O = 2.830 (3) Å and O—H·O = 169°]. One close inter­molecular C—H·O contact exists involving the carbonyl group.