Showing papers in "Australian Journal of Chemistry in 1993"
TL;DR: In this paper, the structures of six new polyaromatic alkaloids from the marine ascidian Didemnum sp. were deduced by high-field n.m. spectroscopy including 13C-1H shift-correlated two-dimensional (2D) n.O.
Abstract: Six new polyaromatic alkaloids, lamellarin I (3), J (6), K (7), L (9), M (11) and the triacetate (13) of lamellarin N, and four known alkaloids, lamellarin A (I), B (15), C (16) and the triacetate (14) of lamellarin D, have been isolated from the marine ascidian Didemnum sp. The structures were deduced by high-field n.m.r. spectroscopy including 13C-1H shift-correlated two-dimensional (2D) n.m.r. experiments and n.O.e . measurements. The triacetates (8) and (10) of two of the compounds, lamellarin K (7) and lamellarin L (9), were dehydrogenated in high yield by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in ethanol heated under reflux. The products obtained were identical in all respects to the triacetates of lamellarin M and N, respectively. The re-isolation of lamellarins A-D, which were previously obtained from the prosobranch mollusc Lamellaria sp., lends further support for the idea that these molluscs sequester the compounds from ascidians as food sources.
94 citations
TL;DR: In this article, the powder neutron diffraction pattern of pyrolusite, β-MnO2 [P42/mnm, No. 136, a = 4.4041(1), c = 2.8765(1)Ǻ], has been refined by the Rietveld method to give values for both the oxygen position parameter u=0.3046(1).
Abstract: The powder neutron diffraction pattern of pyrolusite, β-MnO2 [P42/mnm, No. 136, a = 4.4041(1), c = 2.8765(1)Ǻ], has been refined by the Rietveld method to give values for both the oxygen position parameter u=0.3046(1) and the anisotropic thermal parameters. The data confirm the MnO6 octahedra to be elongated with two long [1.894(1)Ǻ] and four short [1.882(2)Ǻ] Mn-O bond distances. The effect of the stereochemistry on the thermal vibrations is discussed.
80 citations
TL;DR: The monotosylates obtained by treatment of α- and β- cyclodextrin with p- methylbenzenesulfonyl chloride reacted with ammonia to give the title compounds are of unusually low basicity, with pKa values of 8.70 and 8.72, respectively.
Abstract: The monotosylates obtained by treatment of α- and β- cyclodextrin with p- methylbenzenesulfonyl chloride reacted with ammonia to give the title compounds. These amines are of unusually low basicity , with pKa values of 8.70 and 8.72, respectively. In water at 25°, the hydrochloride salt of the amine derived from β- cyclodextrin is approximately 40 times more soluble than β-cyclodextrin and, through complexation, the salt increases the solubility of Nabumetone over 800 times.
61 citations
TL;DR: In this paper, the erbium complex has been shown to be monomeric with eight coordination of the metal and a trigonal bipyramidal arrangement of the centre (Cen) of the N-N bonds of three η2-3,5-diphenylpyrazolate groups.
Abstract: From reaction of lanthanoid metals with bis ( pentafluorophenyl )mercury and 3,5-diphenylpyrazole (HPh2pz) in 1,2-dimethoxyethane ( dme ) and treatment of the products with triphenylphosphine oxide, the complexes [ Ln (η2-Ph2pz)3(OPPh3)2].( dme )n ( Ln = Er or Nd , n = 1; Ln = La, n = 0.6) have been isolated. An X-ray crystal structure shows that the erbium complex [monoclinic, space group C2, a 22.08(3), b 14.30(1), c 13.37(1) Ǻ, β 124.09(7)°, Z 2 2730 'observed' data refined to R 0.046] is monomeric , with eight coordination of the metal. There is a trigonal bipyramidal arrangement of the centre ( Cen ) of the N-N bonds of three η2-3,5-diphenylpyrazolate groups ( ΣCen-Er-Cen 360°; ( Er -N) 2.344 Ǻ) and the oxygens of two equivalent trans triphenylphosphine oxide ligands [O- Er -O 176(1)°; Er -O 2.207(9)Ǻ]. Unit cell data indicate that the neodymium analogue [monoclinic, space group C2, a 23.01(3), b 14.94(2), c 13.82(2) Ǻ, β 123.65(8)°] is isostructural with the erbium complex. An analogous reaction of lanthanum or neodymium metal, Hg(C6F5)2, and HPh2pz in tetrahydrofuran ( thf ) gives [ Ln (η2-Ph2pz)3( thf )3]. thf ( Ln = La or Nd ). The X-ray crystal structure of the neodymium complex [orthorhombic, space group P212121, a 14.009(9), b 16.280(8), c 22.640(16)Ǻ, Z 4, 2967 'observed' data refined to R 0.046 reveals a nine-coordinate monomer with three η2-Ph2pz ligands [ Nd -N 2.420(10)-2.524(8)Ǻ] and three thf ligands [ Nd -O 2.497(8)-2.587(8)Ǻ]. There is a trigonal prismatic arrangement of the centres of the N-N bonds and the oxygen donor atoms.
56 citations
TL;DR: In this paper, the X-ray crystal structure of Yb (OC6H2But3-2,4,6)2( thf )3 is described.
Abstract: Lanthanoid (II) complexes of bulky aryl oxides, Ln (OC6H2But2-2,6-X-4)2 ( Ln = Yb or Eu ; X = H, Me or But) have been prepared by one or more of the following methods: ( i ) reaction of Ln (C6F5)2 with the appropriate phenol, (ii) reaction of the lanthanoid metal, Hg(C6F5)2 and the phenol, and (iii) reaction of the lanthanoid metal with the corresponding thallium(I) phenolate, in tetrahydrofuran ( thf ), and they have been isolated as Ln (OC6H2But2-2,6-X-4)2(thf)3 complexes. Crystallization of Yb (OC6H2But2-2,6-X-4)2( thf )3 (X = H or Me) from toluene yields Yb (OC6H2But2-2,6-X-4)2( thf )2. The X-ray crystal structure of [ Yb (OC6H2But3-2,4,6)2( thf )3]. thf [monoclinic, a 10.20(1), b 32.97(2), c 16.018(4) Ǻ, β 93.52(8)°, V 5375 Ǻ3, Z 4, 2734 'observed' data refined to R 0.070] shows distorted square pyramidal five coordination for ytterbium with an apical thf oxygen [ Yb -O 2.44(1)Ǻ], and transoid phenolate oxygens [ Yb -O 2.21(1), 2.22(1)Ǻ, O- Yb -O 149.0(6)°] and trans thf oxygens [ Yb -O 2.47(2), 2.48(1)Ǻ, O-Yb -O 177.3(5)°] in the square plane. Four methyl groups ( Yb…C 3.89-4.15 Ǻ) across the square plane away from the apical oxygen may block coordination of an additional ligand. X-Ray structures of Yb (OC6H2But2-2,6-Me-4)2(thf)n showing four coordination (n = 2) and five coordination (n = 3), given in a preliminary communication,1 are further discussed.
51 citations
TL;DR: The R3PAuSC(= NPh )OR′, R = Et, Ph or Cy and R′ = Me, Et, Pr, Pri or Cy, have been prepared and characterized by spectroscopic methods as mentioned in this paper.
Abstract: The title compounds, R3PAuSC(= NPh )OR′, R = Et, Ph or Cy and R′ = Me, Et, Pr, Pri or Cy, have been prepared and characterized by spectroscopic methods ( i.r., 1H and 13C n.m.r. and f.a.b . m.s .) and, in the case of the R = Ph and R′ = Me compound, by single-crystal X-ray diffraction methods. The spectroscopic data are consistent with the R3PAu moiety being coordinated by the sulfur atom of the thiolate ligand. This has been confirmed by an X-ray study on Ph3PAuSC(= NPh )OMe which shows the gold atom to be linearly coordinated by the phosphorus and sulfur atoms; Au-P(1) 2.258(1), Au-S(1) 2.301(1) Ǻ and P-Au-S 177.7(1)°. Crystals of Ph3PAuSC(= NPh ) OMe are triclinic, space group pī, with unit cell dimensions: a 10.825(1), b 12.553(2), c 8.914(2) Ǻ, α 97.86(2), β 93.79(1), γ 88.60(1)°, V 1197.1 Ǻ3, Z 2. The structure was refined by a full-matrix least-squares procedure to R 0.028 for 4409 reflections with I ≥ 2.5σ(I).
50 citations
TL;DR: In this paper, a single-beam microcrystal absorption spectrometer system is described that operates in the range 300-2600 nm, on crystals smaller than 50 μm, in the temperature range 5-300 K, with resolution better than 1 cm-1.
Abstract: A single-beam microcrystal absorption spectrometer system is described that operates in the range 300-2600 nm, on crystals smaller than 50 μm , in the temperature range 5-300 K, with resolution better than 1 cm-1. The computer control of data acquisition and baseline storage with interpolation generates data of exceptional quality, and simplifies operation. The salient features of the apparatus are discussed, and the optimal sample absorption is calculated. Examples of optical spectra with relevance to some current interests in inorganic chemistry are provided.
50 citations
TL;DR: In this paper, a new C25 highly branched alkadiene (5) has been isolated from the diatomaceous benthic microbial communities of Hamelin Pool, Western Australia.
Abstract: A new C25 highly branched alkadiene (5) has been isolated from the diatomaceous benthic microbial communities of Hamelin Pool, Western Australia. The structure (5) was determined by detailed n.m.r. and mass spectral analysis, as well as by chemical degradation. Carbon isotopic measurements on this and related isoprenoids were consistent with an origin from diatoms. The role of (5) and related metabolites as biological marker compounds is discussed.
45 citations
TL;DR: In this article, the structure determination of 2,6-bis(1,2,4-triazol-3-yl)pyridine is confirmed by coordination of the unsubstituted ligand through N4 of the triazolyl moieties.
Abstract: Iron(II) and nickel(II) bis ( ligand ) complexes of 2,6-bis(1,2,4-triazol-3-yl)pyridine and the substituted derivatives 2,6-bis(1(N)-methyl-1,2,4-triazol-3-yl)pyridine 2,6-bis(5-methyl-1,2,4-triazol-3-yl)pyridine and 2,6-bis(1,5-dimethyl-1,2,4-triazol-3-yl)pyridine have been prepared. Coordination of the unsubstituted ligand through N4 of the triazolyl moieties is confirmed by structure determination of [FeL2][NO3]2.4H2O and [NiL2]Cl2.3H2O. In both of these complex salts there is an extensive hydrogen-bonded network involving the N 1-H group, the anions and the water molecules. Bis [2,6-bis(1,2,4-triazol-3-yl)pyridine]nickel(II) dichloride trihydrate : monoclinic, space group C2/c, a 17.971(5), b 11.433(1), c 14.849(5) Ǻ, β 122.20(1)°, Z 4. Bis [2,6-bis(1,2,4-triazol-3-yl)pyridine]iron(II) dinitrate tetrahydrate : tetragonal, space group 141/a, a 11.488(2), c 21.055(7) Ǻ, Z 4. [FeL2]Cl2.3H2O is isostructural with the nickel complex and is high-spin but undergoes a partial transition to low-spin at low temperature. Conversion to low-spin is complete when the complex is dehydrated, and this change is associated with the effects of the hydrogen bonding. The solid iron complexes of the N-methyl-substituted ligands in which the hydrogen-bonding potential is reduced are entirely high-spin down to 77K. The complex of the 5-methyl derivative undergoes a continuous singlet ↔ quintet transition below room temperature.
43 citations
TL;DR: In this article, the X-ray crystal structure of bis [2-(pyridin-2′-yl)phenyl]mercury has been shown to have strong linear two-coordination.
Abstract: 2-(Pyridin-2'-yl) phenylmercuric acetate has been prepared by mercuration of 2-phenylpyridine. Symmetrization of the corresponding chloride by alkaline sodium stannite gave bis [2-(pyridin-2'-yl)phenyl]mercury, which was also prepared from 2-(2'-aminophenyl)pyridine by the diazo method and treatment of the initial product with copper powder and aqueous ammonia. Mercuration of benzo [h] quinoline and 3,4,5-trimethyl-1-phenylpyrazole with mercuric acetate followed by treatment with lithium chloride yielded benzo [h]quinolin-10-ylmercuric chloride and 2-(3',4',5'-trimethylpyrazol-1'-yl) phenylmercuric chloride respectively. Treatment of the former product with tribromide ions gave 10-bromobenzo[h] quinoline. The exchange Grignard reaction between 1-phenylpyrazole and ethylmagnesium bromide to give 2-(pyrazol-1'-yl) phenylmagnesium bromide has been monitored by reactions with benzonitrile and D2O to establish optimum conditions for reaction with mercuric bromide giving bis [2-(pyrazol-1'-yl)phenyl]mercury. The 199Hg n.m.r. chemical shifts of the majority of mercurials are shifted substantially downfield relative to the corresponding simple phenylmercurials consistent with weak intramolecular coordination by the heterocyclic nitrogen donor atoms, but a small upfield shift is observed for bis [2-(pyrazol-1'-yl)phenyl]mercury. The X-ray crystal structure of bis [2-(pyridin-2′-yl)phenyl]mercury [monoclinic, space group P21/n, a 12.746(2), b 11.660(2), c 5.698(1) Ǻ, β 92.81(1)′, V 845.8 Ǻ3] shows a centrosymmetric molecule with strong linear two coordination [Hg-C 2.098(8) Ǻ; C-Hg-C 180.0°] and significant but much weaker Hg-N interactions [Hg-N 2.798(7) Ǻ; N-Hg-N 180.0°] giving overall distorted square planar stereochemistry. The phenyl rings are mutually coplanar, whilst the two pyridin-2'-yl rings are parallel and inclined at 10.8° to the phenyl groups.
42 citations
TL;DR: The structures of Bi3Ru3O11, a = 9.3050(2)Ǻ, Pn3, and Bi2Ru2O7, a= 10.2957(1)ǚ, Fd3m, have been determined by Rietveld analysis of powder neutron diffraction data.
Abstract: The structures of Bi3Ru3O11, a = 9.3050(2)Ǻ, Pn3, and Bi2Ru2O7, a = 10.2957(1)Ǻ, Fd3m, have been redetermined by Rietveld analysis of powder neutron diffraction data. For both compounds there is no evidence for appreciable oxygen non- stoichiometry . X-Ray photoelectron spectra of both compounds show unusual line shapes. In the case of Bi3Ru3O11 this is a result of the mixed valency and surface oxidation. In Bi2Ru2O7 final state effects appear to be important.
TL;DR: In this article, the fresh leaves of Ophiorrhiza filistipula (Rubiaceae) have yielded the alkaloids normalindine (2), 7methoxycamptothecin (6) and strictosidinic acid (II).
Abstract: Extraction of the fresh leaves of Ophiorrhiza filistipula ( Rubiaceae ) has yielded the alkaloids normalindine (2), 7-methoxycamptothecin (6) and strictosidinic acid (II). The configurations of the Strychnos alkaloids dolichantoside and isodolichantoside are revised.
TL;DR: In this paper, the pKa values of conjugate acids of substituted pyridine N-oxides in N,N-dimethylformamide (dmf ) and dimethyl sulfoxide (dmnso) solvents were determined potentiometrically for a variety of conjugs.
Abstract: Acidity constants have been determined potentiometrically for a variety of conjugate acids of substituted pyridine N-oxides in N,N- dimethylformamide ( dmf ) and dimethyl sulfoxide ( dmso ). The pKa values in these solvents varied in the same direction and correlated with the pKa values of these species in water and in the protophobic aprotic solvent acetonitrile. Further, a linear relationship has been established between the pKa values in the two protophilic aprotic solvents under study. The most basic substituted pyridine N-oxides exhibited a weak tendency towards cationic homoconjugation in dmf , whereas in the more basic dmso the homoconjugation equilibrium was not established for any of the heterocyclic N-oxides. The phenomenon of cationic homoconjugation was also not observed with pyridine as a representative of heterocyclic amines, both in dmf and dmso. This finding complies with the results obtained in other polar aprotic solvents.
TL;DR: In this article, the motives of chemists for engaging in synthesis are discussed, together with desirable developments in the art of synthesis and in the publication of its results, as well as desirable developments for the future of chemical synthesis.
Abstract: Chemical synthesis is defined as the intentional construction of molecules by means of chemical reactions. The motives of chemists for engaging in synthesis are discussed, together with desirable developments in the art of synthesis and in the publication of its results.
TL;DR: In this article, a tetrahydrocannabinol derivative (6) was identified based on one-and two-dimensional n.m.r. experiments at 300 MHz.
Abstract: Extracts of the colonial ascidian Synoicum castellatum have yielded four compounds derived from prenylated hydroquinones . These included a new tetrahydrocannabinol derivative (6), the first to be isolated from a marine source. Its structure was identified on the basis of one- and two-dimensional n.m.r. experiments at 300 MHz. The known quinone (3), the hydroquinone (4) and the chromene (5) were readily identified by spectral comparison with literature values. Cytotoxicity for (6) against a panel of cultured cell lines is reported.
TL;DR: In this article, three new imidazole alkaloids, naamidines Eand F and clathridine C, have been isolated from a sponge Leucetta sp., together with the known imidaze alkaloid naamidine A, pyronaamidine, clathidine and kealiiquinone.
Abstract: Three new imidazole alkaloids, naamidines Eand F and clathridine C, have been isolated from a sponge Leucetta sp., together with the known imidazole alkaloids naamidine A, pyronaamidine, clathridine and kealiiquinone. The predatory nudibranch Notodoris gardineri, which was found feeding on the sponge, contained the known metabolite clathridine. The structures of all compounds were delineated on the basis of one-dimensional and two-dimensional n.m.r. experiments at 300 MHz.
TL;DR: In this article, the isolation and structure elucidation of four new drimane sesquiterpenes (14)-(17) from a southern Australian marine sponge Dysidea sp. were secured by detailed spectroscopic analysis, chemical interconversion and derivatization.
Abstract: This report describes the isolation and structure elucidation of four new drimane sesquiterpenes (14)-(17) from a southern Australian marine sponge Dysidea sp. The structures for (14)-(17) were secured by detailed spectroscopic analysis, chemical interconversion and derivatization. Also reported are the known metabolites (+)- euryfuran (7), dihydropallescensin-2 (18), (-)- pallescensin-A (19) and (-)-7-deacetoxyolepupane (6). The rare co-occurrence of two antipodes, (7) and (19), in the same specimen highlights the dangers in assigning absolute stereochemistry based on 'unproven' biosynthetic relationships. The absolute stereochemistry for (6) has been unambiguously established for the first time by chemical interconversion to (7). Furthermore, the absolute stereochemistry of the new marine metabolites listed above, (14)-(17), were determined by chemical correlation to (6). A biosynthetic and ecological relationship is proposed between the metabolites from Dysidea sp. with the known marine and terrestrial antifeedant polygodial (8). Chemical investigations are reported that support this proposition.
TL;DR: In this article, the macrocyclic ligand trans-6,13-dimethyl and 6,13dinitro-1,4,8,11-tetraazacyclotetradecane (dino) was used to form NiII compounds with the square planar diprotonated ligand.
Abstract: Compounds of NiII with the macrocyclic ligand trans-6,13-dimethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane ( dino ), which is formed by condensation of bis (ethane-1,2-diamine)nickel(II) salts, nitroethane and formaldehyde, are described, together with homologues formed by substituting propane-1,2-diamine and/or 1-nitropropane. The nitro functions of [Ni( dino )]2+ were reduced by catalytic hydrogenation to form (trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II), [Ni( diam )]2+, isolated as approximately equal amounts of two isomeric forms; designated α (with the R,S,R,S configuration of the chiral nitrogen centres, overall configuration 1α,4α,6β,8α,11α,13α), and β (with the R,R,S,S, 1α,4β,6α,8β,11α,13β configuration). The α-isomer is metastable, and in solution isomerizes to the β-isomer, with rate constant of 5.0(5)×10-5 s-1 in 2 mol l.-1. NaCl solution at 50°C, the rate of this reaction increasing in both acid and base. Protonation constants (pK at 25°C in 0.1 mol l.-1 NaClO4) for diam are 11.2(1), 9.7(1), 6.2(1), 5.3(1), and for the isomeric nickel(II) cations are α 4.94(2), 2.4(5); and β 4.5(1), 4.0(1). Compounds of diam with the β-configuration were prepared with triplet ground state NiII with diam in hexadentate coordination (e.g. β-[Ni(diam-N4)] Cln ) and in tetradentate coordination with the neutral (e.g. trans-β-[Ni(diam-N4)(NCS)2]) or diprotonated ligand (e.g. trans-β-[Ni(diamH2-N4)(NCS)2](CNS)2). Compounds prepared with the α-configuration with triplet ground-state NiII had pentadentate diam with the neutral (e.g. trans-α-[Ni(diam-N5)(H2O)]Cl2) or monoprotonated ligand (e.g. trans-α-[Ni(diamH-N5) Cl ] (ClO4)2). Singlet ground-state NiII compounds with the square planar diprotonated ligand were prepared for both configurations. Structures are reported for β-[Ni(diam-N6)](ClO4)2(H2O), R 0.062 for 5708 reflections; β-[Ni(diam-N6)] [ZnCl4].1.5H2O, R 0.064 for 4332 reflections; β-[Ni(diam-N6)]Cl2.6H2O, R 0.044 for 2001 reflections; trans-β-[Ni(diam-N4)(NCS)2] R 0.056 for 1521 reflections; and trans-α-[Ni(diamH-N5) Cl ](ClO4)2(H2O), R 0.047 for 2667 reflections.
TL;DR: A chemical investigation of a large purple sponge, Spongia sp.,* from the Great Australian Bight, resulted in the isolation of a new sesquiterpene/quinone (8), together with the known compounds dehydrocyclospongiaquinone-1 (4) and spongia quinone (2), the last compound was also isolated as the potassium salt as discussed by the authors.
Abstract: A chemical investigation of a large purple sponge, Spongia sp.,* from the Great Australian Bight, resulted in the isolation of a new sesquiterpene/quinone (8), together with the known compounds dehydrocyclospongiaquinone-1 (4) and spongiaquinone (2). The last compound was also isolated as the potassium salt (9), this being the first recorded account of a naturally occurring marine sesquiterpene/quinone salt. The structure for (8) was assigned by detailed spectroscopic analysis. A re-investigation into the stereostructure of spongiaquinone (2) resulted in the first unambiguous assignment of absolute stereochemistry, and uncovered the peculiar chiroptical properties of spongiaquinone (2) and its potassium salt (9).
TL;DR: In this article, the presence and position of Asn, Arg and Lys residues in dipeptides were determined from a consideration of the collisional activation mass spectra of the (M-H)- ions formed by fast atom bombardment.
Abstract: The presence and position of Asn, Arg and Lys residues in dipeptides may be determined from a consideration of the collisional activation mass spectra of the (M-H)- ions formed by fast atom bombardment. All spectra show the basic dipeptide cleavage, i.e. NH2CH(R1)CONHCH(R2)CO2- → NH2C(R1)CONHCH(R2)CO2H → NH2C(R1)=C=O + -NHCH(R2)CO2H. There are a number of fragmentations characteristic of a particular α side chain: for example, Arg loses HN=C=NH (42 u).
TL;DR: By use of t-butyl 3-[ chloro ( methoxy ) phosphorothioylamino ] propanoate (1), a general method was developed that allowed the preparation of analogues of specific organothiophosphates ; these analogues are suitable for use as haptens in the development of tests for detection of the individual organophosphate as discussed by the authors.
Abstract: By use of t-butyl 3-[ chloro ( methoxy ) phosphorothioylamino ] propanoate (1), a general method was developed that allowed the preparation of analogues of specific organothiophosphates ; these analogues are suitable for use as haptens in the development of tests for detection of the individual organophosphates. The bifunctional reagent (1) was conveniently prepared from readily available starting materials.
TL;DR: In this paper, the synthesis of chiral (2S)- and (2R)-4-methyleneoxazolidin-5-ones, in high enantiomeric purity from (S)-S- methylcysteine, and their highly exo-selective Diels-Alder reactions with cyclic dienes are described.
Abstract: The synthesis of chiral (2S)- and (2R)-4-methyleneoxazolidin-5-ones, in high enantiomeric purity from (S)-S- methylcysteine, and their highly exo-selective Diels -Alder reactions with cyclic dienes are described. (1R,2S,4S)-2-Aminobicyclo[2.2.1]heptane-2-carboxylic acid has been prepared in 92% e.e. by these methods. A number of the products have been characterized by single-crystal X-ray methods, and their structure systematics examined.
TL;DR: In this paper, an X-ray crystal structure analysis on the calixarene tetraphosphate was performed and it was shown that it has a somewhat distorted conformation with an unusual orientation of one of the t-butyl substituents into the cone cavity.
Abstract: The hydroxide ion catalysed phosphorylation of p-t- butylcalix [4] arene by diethyl chlorophosphate under heterogeneous conditions shows a marked sensitivity to the nature of the phase transfer catalyst used. Thus, substitution of tetraethylammonium bromide for the tetrabutylammonium bromide prescribed for the synthesis of the calixarene tetraphosphate leads to a major reaction product becoming a bis (phosphate) in which the calixarene binds as a unidentate ligand to one phosphorus and as a bidentate ligand to the other. An X-ray crystal structure analysis on this new compound shows the calixarene to adopt a somewhat distorted 'cone' conformation with an unusual orientation of one of the t-butyl substituents into the cone cavity. It also reveals that a significant diastereoselectivity must operate in the formation reaction. The only other reaction product detected in this system appears to be the calixarene tetraphosphate in a partial cone conformation.
TL;DR: In this paper, a number of α-methylene-γ-butyrolactone derivatives underwent 1,3-dipolar cycloaddition with propionitrile oxide to give spiro Δ2-isoxazolines.
Abstract: A number of γ-substituted α-methylene-γ-butyrolactone derivatives underwent 1,3-dipolar cycloaddition with propionitrile oxide to give spiro Δ2-isoxazolines. The reaction proceeded regiospecifically and with high diastereoselectivity. The products of anti addition predominated. The regiochemistry of addition and relative stereochemistry of the products were determined by a combination of n.O.e ., HETCOR and DOUBTFUL n.m.r. experiments. The assignment was confirmed in one case by X-ray crystallography.
TL;DR: The ligand sarcophagine ( sar = 3,6,10,13,16,19-hexaazabicyclo[6.6] icosane ) rapidly reacts with [ Mn (OH2)6]2+ to form the nearly colourless [Mn ( sar )]2+ ion, which can readily be oxidized to the bright orange [mn( sar )]3+ ion (E°′+0.53 V v. n.h.
Abstract: The ligand sarcophagine ( sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ) rapidly reacts with [ Mn (OH2)6]2+ to form the nearly colourless [ Mn ( sar )]2+ ion, which can readily be oxidized to the bright orange [Mn ( sar )]3+ ion (E°′+0.53 V v. n.h.e. in 0.1 mol l-1 CF3SO3H at 295 K). A single-crystal structure determination on [ Mn ( sar )](NO3)3, space group I 42d, a 15.549(6), c 19.014(6) Ǻ, R 0.051, Rw 0.049 for 608 'observed' reflections, shows the coordination geometry of the manganese(III) ion, with site symmetry 2, to be subject to a Jahn-Teller distortion, giving three pairs of Mn -N bond lengths of 2.18(1), 2.13(1) and 2.08(1)Ǻ. The [ Mn ( sar )]3+ ion is stable in strongly acidic aqueous solutions, but in solutions of pH > 3 undergoes deprotonation and subsequent disproportionation reactions. The manganese(II) complex ion is less stable in acidic solutions, undergoing hydrolysis at a rate showing a first-order dependence on both proton and chloride ion concentrations. Both [ Mn ( sar )]2+ and [ Mn ( sar )]3+ can be obtained in chiral forms, and the rate constant for electron self-exchange obtained by polarimetric measurements on solutions of mixtures of [ Mn ( sar )]2+ and [ Mn ( sar )]3+ of opposite chirality is 30 dm3 mol-1s-1 at 298 K, I = 0.1 M.
TL;DR: In this paper, the synthesis and characterization of eight new 14 to 17-membered macrocycles incorporating O2N2-donor sets in the rings and pendant 2-pyridylmethyl or diethylaminoethyl groups, attached at one or both ring nitrogens, are reported.
Abstract: The syntheses and characterization of eight new 14 to 17-membered macrocycles incorporating O2N2-donor sets in the rings and pendant 2-pyridylmethyl or diethylaminoethyl groups, attached at one or both ring nitrogens , are reported. The X-ray structure of the mono(2-pyridylmethyl) derivative of the 15-membered macrocycle at c. 120 K is also described.
TL;DR: For example, this paper showed that the structure of the podand ligand complexes Λ-[Co(NO2sen)]Cl3.2H2O [orthorhombic, space group P 212121, a 18.10(2)°; R 0.051 for No 26441 show very close configurational and conformational similarities to those of the cage complexes.
Abstract: On the basis of structural comparisons involving intermediates and side products of encapsulation reactions as well as several cage complexes, the efficiency of the base- catalysed reaction between formaldehyde, nitromethane and [Co(en)3]3+ (en = ethane-1,2-diamine) to give [Co((NO2)2sar)]3+ appears to be explicable in terms of the 'interlocking' of constituent parts without appreciable concomitant bond length or bond angle distortions. Thus, the structures of the podand ligand complexes Λ-[Co(NO2sen)]Cl3.2H2O [orthorhombic, space group P 212121, a 18.755(6), b 11.598(4), c 9.164(3) Ǻ; R 0.038 for No 1735 'observed' reflections] and Δ,Λ-[Co(Nt-Me,NO2sen)]Cl3.4H2O [monoclinic, P21/n, a 18.613(5), b 9.301(3), c 13.779(4) Ǻ, β 107.10(2)°; R 0.051 for No 26441 show very close configurational and conformational similarities to those of the cage complexes Δ,Λ-[Co(NO2azasar)]Cl3.3H2O [monoclinic, P 21/c, a 9.339(3), b 15.479(9), c 17.360(7)Ǻ, β 114.15(3)°; R 0.048 for No 2612], Δ,Λ-[Co((NO2)2sar)]Cl3.2H2O [triclinic, Pī , a 13.592(3), b 10.024(3), c 9.772(3)Ǻ, α 62.89(2),β 82.96(3), γ 85.15(2)°; R 0.045 for No 5646] and Δ,Λ-[Co((OH)2sar)]Cl3.3H2O [monoclinic, P21/c, a 15.97(1), b 8.758(4), c 16.760(4)Ǻ, β 98.72(4)°; R 0.052 for No 2400], as well as to published structures of [Co(en)3]3+, [Co(tame)2]3+ [tame = 1,1,1-tris- ( aminomethyl )ethane = ethylidynetris ( methanamine )] and other cage complexes. Some of these similarities may be associated with common hydrogen-bonding patterns in the solids resulting from anion ' chelation' by adjacent NH moieties in the metal ion coordination spheres. Necessary caution in relating structural and electronic properties is implied by the structure determination for Δ,Λ [Co(Cl,ClCH2absar)](NO3)3 [monoclinic, P 21/c, a 14.750(6), b 9.264(3), c 17.959(7) Ǻ, β 95.80(3)°; R 0.061 for No 1431], one of the products of molecular rearrangement following nitrosation of [Co((NH2)2sar)]3+. Despite marked electronic spectral and electrochemical differences with its parent complex, [Co(Cl,ClCH2absar)](NO3)3 contains cobalt(III) in a coordination environment which remains similar to those in more symmetrical cage complexes.
TL;DR: In this article, the diterpenoids aplyviolene, norrisolide, spongian-16-one, chelonaplysin C, cheloviolene A-F and chelo-liolin were identified from New Zealand coastal waters.
Abstract: The sponge Chelonaplysilla violacea, collected from New Zealand coastal waters, contains as major constituents the diterpenoids aplyviolene (1a), norrisolide (2), dendrillolide A (3) aplyroseol-7 (4), spongian-16-one (5), chelonaplysin C (6), and a series of new compounds cheloviolene A-F and cheloviolin. Structures were assigned to cheloviolene A (7), [3aR-[3aα,4α(1R*,3aR*,8aS*),5β,6aα]]-5-hydroxy-4(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydrofuro [2,3- b] furan-2(3H)-one, cheloviolene B (8), [3aR-[3aα,4a(1R*,3aR*, 8aS*),5α,6aα]]-5-hydroxy-4-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydrofuro [2,3-b]furan-2(3H)-one, cheloviolene C (9), [1'ξ(1R*,3aS*,7aS*),4ξ]-4-[1′-( acetyloxymethyl )-2′-(4,4,7a-trimethyloctahydro-1H-inden-1-yl)prop-2′-enyl] dihydrofuran -2(3H)-one, cheloviolene D (10), methyl [3α,4α(1R*,3aR*,8aS*)]-5-oxo-4-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl)tetrahydrofuran-3-acetate, cheloviolene E (11), methyl [3α,4α-(1R*,3aS*,7aS*)]-5-oxo-4-[1′-(4,4,7a-trimethyloctahydro-1H-inden-1-yl) ethenyl ]tetrahydrofuran-3-acetate, and cheloviolene F (12), [4ξ,5ξ(1R*,3R*,8aS*)]-4-( acetyloxymethyl )-5-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydro-2H-pyran-2-one, by using spectroscopic methods; the structure (13) was deduced for cheloviolin, [1S-[1α,5α,6α,8R*(1aS*,3aS*,7aS*,7b-R*)]]-6-acetyloxy-8-(4,4,7a-trimethyldecahydrocylopropa[a] naphthalen-la-yl )-2,7-dioxabicyclo- [3.2.1]octan-3-one.
TL;DR: In this article, the synthesis of diaminosarcophagine and manganese(II) complexes of the cage amine ligand diamino-arcophage ( di-aminosarcophagus = (NH2)2sar = 1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6] icosane ) in its diprotonated form are recorded, together with their single-crystal X-ray structure determinations at c. 295 K.
Abstract: The syntheses of [ Mn ((NH3)2sar)](NO3)4.H2O and [ Mn ((NH3)2sar)](NO3)5.2H2O, manganese(II) and manganese(III) complexes of the cage amine ligand diaminosarcophagine ( di-aminosarcophagine = (NH2)2sar = 1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ) in its diprotonated form are recorded, together with their single-crystal X-ray structure determinations at c. 295 K. The monoclinic P21 array of the manganese(II) complex (a 12.386(5), b 12.431(4), c 8.598(4) Ǻ, β 93.89(4)°, V 1321(1) Ǻ3,Z 2) is archetypical for similar complexes of a wide variety of transition metals; for the present determination, R was 0.027 for 2013 'observed' (I > 3σ(I)) reflections. The manganese(III) complex is monoclinic C 2/c, a 10.744(2), b 13.294(4), c 20.462(9) Ǻ, β 102.38(3)°, Z 4; R was 0.055 for 1629 'observed' reflections. Both structures show the six secondary nitrogen atoms of the ligand to be bound to the manganese ion in a configuration approximately halfway between a trigonal prism and an octahedron. The ligand is in the lel3 conformation. In the first complex, Mn -N distances, appropriate to high-spin manganese(II), range from 2.228(3) to 2.253(3) Ǻ, mean 2.238 Ǻ; in the second, surprisingly, the distances are even more closely ranged (unlike those of the sarcophagine analogue of the previous paper), 2.115(4)-2.127(4) Ǻ, the mean (2.122 Ǻ) being closely comparable to that recorded for the sar analogue, and show no appreciable variation attributable to the expected Jahn-Teller effect.
TL;DR: In this paper, the structures of these compounds were delineated on the basis of one and two-dimensional n.m.r. experiments at 300 MHz, and confirmed by the total synthesis of one of them.
Abstract: Samples of colonial ascidians, Aplidium sp., have yielded three novel iodinated L-tyrosine alkaloids (1)-(3). The structures of these compounds were delineated on the basis of one and two-dimensional n.m.r. experiments at 300 MHz, and confirmed by the total synthesis of one of them (2).