Treatment of hydrogen bonding in SINDO1

For the treatment of hydrogen bonding in SINDO1, 2p orbitals are introduced on hydrogen. The optimization of the orbital exponent together with the generation of approximate formulas for the core attraction integrals is sufficient to obtain good geometries and binding energies in hydrogen bonded systems. The method is applied to the dimers (H₂O)₂, (NH₃)₂, (HF)₂, (HCOOH)₂, (HCN)₂, (H₂S)₂, and (HCI)₂, mixed dimers NH₃ · H₂O and H₂O · HCN, and cyclic polymers (HF)_n(n = 3, 4, 6). © 1993 John Wiley & Sons, Inc.     

Darstellung und Struktur der Komplexverbindungen trans‐[CoIII(py)4F2][H2F3] und [Pd(py)4]F2 · 1,5 HF · 2 H2O

Synthesis and Crystal Structures of the Complexes trans ‐[Co^III(py)₄F₂][H₂F₃] and [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O The cobalt complex trans‐[Co(III)(py)₄F₂][H₂F₃] ( 1 ) has been prepared by electrochemical oxidation of CoF₂ in a pyridine/HF mixture and the palladium complex [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O ( 2 ) has been obtained via halogen exchange between Pd(py)₂Cl₂ and AgF₂ in pyridine. 1 and 2 crystallize in the space group C2/c with a = 27.928(14), b = 9.019(3), c = 18.335(8) Å, β = 113.41(3)° for 1 and a = 28.183(9), b = 9.399(3), c = 17.397(6) Å, β = 104.66(3)° for 2 , respectively. Concerning the shape and location of the M(py)₄ fragments 1 and 2 are isostructural. The metal atoms occupy special positions in their unit cells with the result that four complex atoms have C₂ symmetry and four complex cations have C_i symmetry giving a total of Z = 8. In 1 two F^– ions complete an octahedral coordination around the Co atoms (Co–F 1.820(2) to 1.834(3) Å). In 2 the shortest Pd–F distance is 3.031(2) Å. This precludes the existence of Pd–F bonds. In 1 one can identify H₂F₃^– groups. In 2 there are larger aggregates, consisting of F^–, HF, and H₂O subunits, connected by H‐bridges. In spite of these differences, both complexes belong to the same type of structure, which may be of a common type M^x+(py)₄F_x · y HF · z H₂O.     

Structure of heteroassociates formed in the HF-(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>2</Subscript>O liquid system

The aim of this work was to determine the structure of stable heteroassociates (HAs) with the stoichiometric ratios 1:2, 2:1, and 4:1 of molecules formed in the HF-(C₂H₅)₂O binary liquid system. The stretching frequencies of HF molecules found for each HA using a special procedure for processing IR spectra were compared with the calculated frequencies V HF of the stable molecular complexes (HF)_m ((C₂H₅)₂O)_n (m = 1, 2, 4, 8; n = 1, 2) with different topologies by the density functional method (B3LYP/6-31++G(d,p)). As a result, it was shown that the most stable (among H-bonded complexes with the same stoichiometric ratio of molecules) HAs HF((C₂H₅)₂O)₂, (HF)₄ ((C₂H₅)₂O)₂, and (HF)₈-((C₂H₅)₂O)₂ formed in HF solutions in diethyl ether. All of them had a cyclic structure and a common peculiarity of structure: only one lone electron pair of the oxygen atom of the (C₂H₅)₂O molecules is involved in hydrogen bonding.     

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.     

Two stereoisomeric pentacyclic oxin­dole alkaloids from Uncaria tomentosa: uncarine C and uncarine E

The chloro­form solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octa­hydro‐1′‐methyl‐2‐oxospiro­[3H‐indole‐3,6′(4′aH)‐[1H]­pyrano­[3,4‐f]indolizine]‐4′‐carboxyl­ic acid methyl ester, C₂₁H₂₄N₂O₄·CHCl₃, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C₂₁H₂₄N₂O₄, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the ox­indole, with N?O distances in the range 2.759 (4)–2.894 (5) Å.     

Transition state geometry in radical abstraction reactions: comparison of interatomic distances in the intersecting parabolas and Morse curves models with quantum-chemical calculations

Interatomic distances in the transition state were estimated for the reactions of radical abstraction: H^· + H₂, H^· + HCl, H^· + CH₄, N^·H₂ + NH₃, HO^· + H₂O, HO₂ ^· + HOOH, and C^·H₃ + SiH₄. The calculation was performed by the quantum-chemical density functional method or coupled clusters method (QCH), as well as by the methods of intersecting parabolas (IPM) and Morse curves (IMM), using experimental data (activation energies and reaction enthalpies). The results of the latter two methods are close to the quantum-chemical calculation and differ only by the increment a: r(IPM or IMM) = a + r(QCH), where a = –4.5·10^–12 m for IPM and a = +1.9·10^–12 m for IMM.     

Structural and theoretical study of four novel norcantharidine derivatives: two new cases of conditional isomorphism

Structural and theoretical studies of four novel 5,6‐dehydronorcantharidine ( DNCA )/norcantharidine ( NCA ) derivatives, namely (3aR,4S,7R,7aS)‐2‐phenyl‐3a,4,7,7a‐tetrahydro‐4,7‐epoxy‐1H‐isoindole‐1,3(2H)‐dione, C₁₄H₁₁NO₃ ( DNCA‐A ), (3aR,4S,7R,7aS)‐2‐(4‐nitrophenyl)‐3a,4,7,7a‐tetrahydro‐4,7‐epoxy‐1H‐isoindole‐1,3(2H)‐dione, C₁₄H₁₀N₂O₅ ( DNCA‐NA ), (3aR,4S,7R,7aS)‐2‐(4‐nitrophenyl)‐3a,4,5,6,7,7a‐hexahydro‐1H‐4,7‐epoxyisoindole‐1,3(2H)‐dione, C₁₄H₁₂N₂O₅ ( NCA‐NA ), and (3aR,4S,7R,7aS)‐2‐(2‐hydroxyethyl)‐3a,4,5,6,7,7a‐hexahydro‐1H‐4,7‐epoxyisoindole‐1,3(2H)‐dione, C₁₀H₁₃NO₄ ( NCA‐AE ), are reported. The supramolecular interactions and single‐crystal structural characteristics of these molecules, together with the crystal structures of four other similar molecules, i.e. NCA‐A (the 4‐phenyl derivative of NCA‐NA ), DNCA‐AE (the 5,6‐unsaturated derivative of NCA‐AE ), DNCA and NCA , were analysed. Surprisingly, DNCA‐A and NCA‐A , as well as DNCA–NA and NCA‐NA , proved to be isomorphic, while DNCA‐AE and NCA‐AE , as well as DNCA and NCA , have very different crystal structures. These are very rare isostructural examples between unsaturated and saturated oxanorbornene/oxanorbornane derivatives. To further explore how noncovalent interactions (NCIs) affect the degree of isomorphism in this particular series of rigid molecules where there is a fairly limited conformational degree of freedom, all four pairs of crystal structures were analyzed in parallel. The differentiation in NCIs which entails the packing mode of similar molecules is supported by energy calculations based on real or exchanged crystal structures. Our results show that minor structural differences may result in very different supramolecular interactions, and so lead to altered packing modes in the crystalline solids. Even if isostructurality sometimes occurs, the possibility of various molecular packing types cannot be ruled out. On the other hand, isomorphism may just be the result of kinetic possibilities instead of relative thermodynamic stabilities. Though crystal structure prediction is formidable, the comparison method based on existing crystal structures and quantum calculations can be used to predict the probability of isomorphism. This understanding will help us to design new norbornene derivatives with specified structures.     

Four novel spirooxazacamphorsultam derivatives

The chiral compounds (6aS,9S,10aR)‐11,11‐dimethyl‐5,5‐dioxo‐2,3,8,9‐tetrahydro‐6H‐6a,9‐methanooxazaolo[2,3‐i][2,1]benzisothiazol‐10(7H)‐one, C₁₂H₁₇NO₄S, (1), (7aS,10S,11aR)‐12,12‐dimethyl‐6,6‐dioxo‐3,4,9,10‐tetrahydro‐7H‐7a,10‐methano‐2H‐1,3‐oxazino[2,3‐i][2,1]benzisothiazol‐11(8H)‐one, C₁₃H₁₉NO₄S, (2), (6aS,9S,10R,10aR)‐11,11‐dimethyl‐5,5‐dioxo‐2,3,7,8,9,10‐hexahydro‐6H‐6a,9‐methanooxazolo[2,3‐i][2,1]benzisothiazol‐10‐ol, C₁₂H₁₉NO₄S, (3), and (7aS,10S,11R,11aR)‐12,12‐dimethyl‐6,6‐dioxo‐3,4,8,9,10,11‐hexahydro‐7H‐7a‐methano‐2H‐[1,3]oxazino[2,3‐i][2,1]benzisothiazol‐11‐ol, C₁₃H₂₁NO₄S, (4), consist of a camphor core with a five‐membered spirosultaoxazolidine or six‐membered spirosultaoxazine, as both their keto and hydroxy derivatives. In each structure, the molecules are linked via hydrogen bonding to the sulfonyl O atoms, forming chains in the unit‐cell b‐axis direction. The chains interconnect via weak C—H...O interactions. The keto compounds have very similar packing but represent the highest melting [507–508 K for (1)] and lowest melting [457–458 K for (2)] solids.     

Preparation and structural analysis of (±)‐cis‐ethyl 2‐sulfanylidenedecahydro‐1,6‐naphthyridine‐6‐carboxylate and (±)‐trans‐ethyl 2‐oxooctahydro‐1H‐pyrrolo[3,2‐c]pyridine‐5‐carboxylate

Bicycle ring closure on a mixture of (4aS,8aR)‐ and (4aR,8aS)‐ethyl 2‐oxodecahydro‐1,6‐naphthyridine‐6‐carboxylate, followed by conversion of the separated cis and trans isomers to the corresponding thioamide derivatives, gave (4aSR,8aRS)‐ethyl 2‐sulfanylidenedecahydro‐1,6‐naphthyridine‐6‐carboxylate, C₁₁H₁₈N₂O₂S. Structural analysis of this thioamide revealed a structure with two crystallographically independent conformers per asymmetric unit (Z′ = 2). The reciprocal bicycle ring closure on (3aRS,7aRS)‐ethyl 2‐oxooctahydro‐1H‐pyrrolo[3,2‐c]pyridine‐5‐carboxylate, C₁₀H₁₆N₂O₃, was also accomplished in good overall yield. Here the five‐membered ring is disordered over two positions, so that both enantiomers are represented in the asymmetric unit. The compounds act as key intermediates towards the synthesis of potential new polycyclic medicinal chemical structures.     

Stereochemical Course of the Formation of the C(7)‐Formyl Group from a Chiral Methyl Group during the Transformation of Chlorophyllide a into Chlorophyllide b

The biosynthesis of chlorophyll a and chlorophyll b from (2R,3R)‐ and (2S,3S)‐5‐amino[2,3‐¹⁴C₂,2,3‐²H₂,2,3‐³H₂]levulinic acid in greening barley has established that chlorophyllide a oxidase catalyses the transformation of the methyl group at C(7) of chlorophyllide a into the CHO group of chlorophyllide b with the loss of H^Si from the 7‐(hydroxymethyl)chlorophyllide intermediate.     

Einfluss von H‐Brückenbindungen auf die Jahn–Teller‐Verzerrung in den Kettenstrukturen von 2,2′‐bipyMn(H2PO4)F2·H2O und 2,2′‐bipyMn(H2PO4)2F

In the system 2,2′‐bipyridine/Mn^III/HF/H₃PO₄/H₂O two compounds with chain structures could be prepared and characterised by X‐ray structure analyses. 2,2′‐bipyMn(H₂PO₄)F₂·H₂O ( 1 ): monoclinic, twinned, space group P2₁/c, Z = 4, a = 6.7883(4), b = 10.9147(5), c = 17.8102(8) Å, β = 100.142(4)°, R = 0.0328. 2,2′‐bipyMn(H₂PO₄)₂F ( 2 ): triclinic, space group P , Z = 2, a = 6.675(1), b = 10.715(1), c = 11.013(1) Å, α = 107.595(9)°, β = 90.994(9)°, γ = 95.784(8)°, R = 0.0252. Both compounds show chain structures with trans‐bridging dihydrogenphosphate ligands and bipy and two fluorine ligands for ( 1 ), or bipy, fluorine and an additional dihydrogenphosphate, respectively, for ( 2 ) in equatorial positions. Due to the pseudo‐Jahn–Teller effect, Mn^III shows elongated octahedral coordination with ferrodistortive ordering along the chain direction. The distortion is remarkably higher in ( 1 ) than in ( 2 ). This is discussed in context with additional hydrogen bonds along the chain in ( 2 ).     

Reactions of photogenerated fluorine atoms with molecules trapped in solid argon

Isolated radicals^.NH₂ and radical-molecule complexes^.NH₂−HF, which are products of the reactions of mobile fluorine atoms with NH₃ molecules in solid argon, were identified by EPR spectroscopy. The isotropic HFC constants of the complex (a _N=1.20,a _H=2.40, anda _F=0.70 mT) were determined experimentally. The constant of isotropic HFC with the nucleus of hydrogen atom of the HF molecule is less than 0.1 mT. This assignment was confirmed in the experiments on isotope substitution of atoms (H→D),¹⁴N→¹⁵N) in the NH₃ molecule. According to quantum-chemical calculations, the free complex^.NH₂−HF has a planar structure withC ₂, summetry and a binding energy of 12 kcal mol⁻¹. Optimization of the arrangement of the complex in the crystal showed that its structure is only slightly distorted in the Ar lattice so that the equilibrium configuration is close to that obtained from gas-phase calculations. Different ratios of relative intensities of the proton triplet lines in the EPR spectra of isolated^.NH₂ radicals and^.NH₂−HF complexes were qualitatively explained by different heights of the barriers to rotation of the NH₂ fragment in the Ar lattice.     

Synthesis of nitrogen-containing drimane sesquiterpenoids from 11-dihomodrim-8(9)-en-12-one

Products from the reaction of 11-dihomodriman-8α-ol-12-one with several reagents such as MeSO₃SiMe₃, CF₃SO₃SiMe₃, Sc(CF₃SO₃)₃, conc. H₂SO₄ in EtOH (30% solution), and Amberlist-15 ion-exchange resin were studied. 11-Dihomodrim-8(9)-en-12-one and its oxime were synthesized. The reaction of its oxime with H₃PO₄ (86%) or CF₃CO₂H produced (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho [1,2-e]-3-methyl-4,5-dihydro-[1,2,6]-oxazine; with p-TsCl in Py, (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1,2-d]-2-methylpyrroline-N-oxide; and with PCl₅ in Et₂O, 11-acetylaminodrim-8(9)-ene and 11-methylaminooxodrim-8(9)-ene.     

Electron correlation in the interacting quantum atoms partition via coupled‐cluster lagrangian densities

The electronic energy partition established by the Interacting Quantum Atoms (IQA) approach is an important method of wavefunction analyses which has yielded valuable insights about different phenomena in physical chemistry. Most of the IQA applications have relied upon approximations, which do not include either dynamical correlation (DC) such as Hartree‐Fock (HF) or external DC like CASSCF theory. Recently, DC was included in the IQA method by means of HF/Coupled‐Cluster (CC) transition densities (Chávez‐Calvillo et al., Comput. Theory Chem. 2015, 1053, 90). Despite the potential utility of this approach, it has a few drawbacks, for example, it is not consistent with the calculation of CC properties different from the total electronic energy. To improve this situation, we have implemented the IQA energy partition based on CC Lagrangian one‐ and two‐electron orbital density matrices. The development presented in this article is tested and illustrated with the H₂, LiH, H₂O, H₂S, N₂, and CO molecules for which the IQA results obtained under the consideration of (i) the CC Lagrangian, (ii) HF/CC transition densities, and (iii) HF are critically analyzed and compared. Additionally, the effect of the DC in the different components of the electronic energy in the formation of the T‐shaped (H₂)₂ van der Waals cluster and the bimolecular nucleophilic substitution between F^– and CH₃F is examined. We anticipate that the approach put forward in this article will provide new understandings on subjects in physical chemistry wherein DC plays a crucial role like molecular interactions along with chemical bonding and reactivity. © 2016 Wiley Periodicals, Inc.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-containing drimane sesquiterpenoids from 11-dihomodriman-8α-ol-12-one

Beckmann reaction products of 11-dihomodriman-8α-ol-12-one oxime with Ac₂O in pyridine, 86% H₃PO₄, p-TsCl in pyridine, and PCl₅ in ether were investigated. It has been found that the major product from treatment of the oxime with Ac₂O is the oxime acetate. Reaction of the oxime with 86% H₃PO₄ gave (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1, 2][5, 6]-3-methyl-4,5-dihydro[1, 2, 6]oxazine; with p-TsCl, (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1, 2][5, 6]-2-methyl-4,5dihydro[1, 3, 6]oxazine; with PCl₅, a mixture of products containing 11-acetylamino- and 11-methylaminooxodrimenes that were isomeric at the double bond, norambreinolide, and a 1,3,6-oxazine.     

XRD and VCD: a marriage of love or convenience? Honeymoon around a cyclic urea derivative

The structures and absolute configurations of the enantiomers (3aR,8aR)‐2,2‐dimethyl‐4,4,8,8‐tetraphenyl‐4,5,6,7,8,8a‐hexahydro‐3aH‐1,3‐dioxolo[4,5‐e][1,3]diazepin‐6‐one 0.33‐hydrate, C₃₂H₃₀N₂O₃·0.33H₂O, (Ia), and (3aS,8aS)‐2,2‐dimethyl‐4,4,8,8‐tetraphenyl‐4,5,6,7,8,8a‐hexahydro‐3aH‐1,3‐dioxolo[4,5‐e][1,3]diazepin‐6‐one 0.39‐hydrate, C₃₂H₃₀N₂O₃·0.39H₂O, (Ib), have been elucidated unambiguously using the complementary power of single‐crystal X‐ray diffraction (XRD) and vibrational circular dichroism (VCD). The enantiomers crystallize in the Sohncke space group P2₁2₁2 and pack as dimers stabilized by two symmetric hydrogen bonds involving one amide group each of the cyclic urea moiety. This double interaction is capped by a water molecule that partially occupies a site lying on the twofold axis and forms an uncommon hydrogen bond between the two monomers. A comparison between the solid‐state VCD characterizations and the Bayesian statistics on Bijvoet differences determined from the XRD measurements reveals a tendency towards the correct determination of the absolute configuration by this latter method.     

Tuning the Adsorption Selectivity of ZIF-8 by Amorphization

Amorphous metal–organic frameworks (a_mMOFs) with a partially collapsed structure are a new category of porous hybrid materials. Here, solid-state amorphization of ZIF-8 was achieved by mechanical compression at 0.75 GPa. The compression-induced amorphous ZIF-8 (a_mZIF-8) had a collapsed structure, but retained partial porosity. Benefiting from the deformed channel, the resultant a_mZIF-8 exhibited preferable adsorption of C₃H₆, resulting in higher thermodynamic adsorption selectivity of C₃H₆/C₃H₈ (6.72) than the crystalline counterparts (1.06). Further, a_mZIF-8 achieved complete separation of an equimolar C₃H₆/C₃H₈ mixture with the first breakthrough of C₃H₈. a_mZIF-8 also displayed an enhancement in CO₂/N₂ and CO₂/CH₄ adsorption selectivities. More importantly, a self-standing a_mZIF-8 membrane with boundary-free microstructure was constructed for the first time, and exhibited separation potential for H₂/CH₄, CO₂/N₂, CO₂/CH₄, and C₃H₆/C₃H₈ with ideal selectivities of 14.79, 12.83, 16.23, and 2.67, respectively.     

Three related benzoannelated diazapolyether macrocycles: effects of macrocycle ring size and position of benzo groups on hydrogen bonding of the amine H atoms

The benzoannelated diazapolyether macrocycles 6,7,9,10,17,18‐hexahydro‐5H,11H‐8,16,19‐trioxa‐5,11‐diazadibenzo[a,g]cyclopentadecene, C₁₈H₂₂N₂O₃, (I), 6,7,9,10,12,13,20,21‐octahydro‐5H,14H‐8,11,19,22‐tetraoxa‐5,14‐diazadibenzo[a,g]cyclooctadecene, C₂₀H₂₆N₂O₄, (II), and 6,7,9,10,17,18,20,21‐octahydro‐16H,22H‐5,8,11,19‐tetraoxa‐16,22‐diazadibenzo[a,j]cyclooctadecene 0.3‐hydrate, C₂₀H₂₆N₂O₄·0.304H₂O, (III), show different patterns of hydrogen bonding. In (I), the amine H atoms participate only in intramolecular hydrogen bonds with ether O atoms. In (II), the amine H atoms form intramolecular hydrogen bonds with the phenoxy ether O atoms and intermolecular hydrogen bonds with alkyl ether O atoms in an adjacent molecule, forming a chain linking the macrocycles together via an R₂²(10) motif. Molecules of (II) were found on a crystallographic twofold axis. In (III), the amine H atoms participate in a hydrogen‐bond network with adjacent ether O atoms and with a water molecule [having a partial occupancy of 0.304 (6)] that links the molecules together via a C₂²(7) motif.     

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.