Robert F. Bryan's research while affiliated with University of Virginia and other places
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Publications (137)
Three compounds containing the [Mo2O2(μ-E)2]2+ (E = O, S) cores ligated by [Fe2S2(CO)6]2- have been prepared and structurally characterized: (Ph4As)2{Mo2O2(μ-S)2[Fe2S2(CO)6]2} ((Ph4As)2I, triclinic, space group P1̄ (No. 2), a = 14.266(12) Å, b = 14.746(12) Å, c =16.643(15) Å, α = 101.9(2)°, β = 98.2(2)°, γ = 99.1(2)°, Z = 2, R = Rw = 0.058, 6196 re...
The authors prepared three compounds with [Mo{sub 2}O{sub 2}({mu}-E){sub 2}]{sup 2+} (E = O, S) core ligated by [Fe{sub 2}S{sub 2}(CO){sub 6}]{sup 2-}. These compounds were characterized by X-ray crystallography and infrared spectroscopy. The three principal compounds consist of bismolybdenum cores bridged by oxygen or sulfur and surrounded by a pa...
This paper reports the controlled synthesis, characterization, and study of a series of pyrrolyl- and phospholyl-containing transition-metal sandwich complexes stabilized by cyclic Et2C2B3H(n)n-7 (n = 3, 5) carborane units, including the first triple-decker complexes of N- or P-containing heterocyclic ligands. The reaction of the nido-Et2C2B4H5- io...
Reaction of [Mo(CO)4I3]- with 2-3 equiv of [Fe2S2(CO)6]2- in THF produces two new Mo-Fe-S-CO clusters, the [MoFe6S6(CO)16]2- (I) and [MoFe4S3(CO)14]2- (II) ions, both of which have been structurally characterized, the latter as its mono(triethylphosphine) substitution product, [MoFe4S3(CO)13(PEt3)]2- (II-P). Crystallographic data: (Ph4As)2(I), tric...
This paper reports the controlled synthesis, characterization, and study of a series of pyrrolyl- and phospholyl-containing transition-metal sandwich complexes stabilized by cyclic Et2C2B3Hnn-7 (n = 3, 5) carborane units, including the first triple-decker complexes of N- or P-containing heterocyclic ligands. The reaction of the nido-Et2C2B4H5- ion...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The conformation of the pyranoid ring of the l-idopyranosyluronic acid residues of heparin and dermatan sulfate is a matter of controversy. X-Ray crystallographic analysis of methyl 6-deoxy-α-d-idopyranoside (4), which has the same relative arrangement of substituents on the pyranose ring, shows that it adopts the 4C1 conformation having the four o...
The reaction of the diamines obtained from (I) with alloxan (II) yields the isoalloxazines (III) accompanied by a minor product.
The reaction of 2-amino-5-chloro-N,4-dimethylaniline with alloxan monohydrate in boric acid-acetic acid mixtures has been shown to produce 7-chloro-8-methylalloxazine (III) in addition to the expected 8-chlorolumiflavin (I). The position of heteroatom substitution in III and I has been verified by optical and 1H NMR studies and by single-crystal X-...
A series of [3]ferrocenophanes of general formula Fe(C5H4E)2Y, (E = S, Se; Y = PC6H5, AsC6H5) has been prepared by the reaction of ferrocene-1,1′-dithiol or ferrocene-1,1′-diselenol with chloride complexes of the Group V elements. The phosphorus containing compounds react with elemental sulfur and with iodomethane to form a phosphine sulfide and a...
A series of [3]ferrocenophanes of general formula Fe(C5H4X)2YCl2 and the spiro compounds [Fe(C5H4X)2]2Ge (X = S, Se; Y = Ge, Sn) have been prepared by the reaction of ferrocene 1,1′-dithiol and ferrocene 1,1′-diselenol with tetrahalides of germanium and tin. Spectroscopic properties of the compounds are reported. In solution, the compounds are flux...
Aus Datisca glomerata wurden die Datiscoside (lal-(lg) bzw. (IIa)-(IIc) isoliert.
Datisca glomerata has been systematically fractionated by following cellular toxicity in an effort to identify previously uncharacterized cytotoxic principles. Several new cucurbitacin glycosides, including datiscosides B(8), C(3), D(9), E(4), F(5), G(6), and H(10) and the known compound datiscoside (1), as well as cucurbitacins B(11), D(2), and F(...
The crystalline phases of certain classes of highly anisotropic organic molecules do not pass directly to isotropic liquids on heating but instead pass through one or more intermediate transitions to yield so-called liquid-crystalli ne mesophases in which the molecular ordering is intermediate between that of a solid and of a true liquid. The relat...
A series of 1,3-diselena-[3] ferrocenophanes of general formula Fe(C5H4Se)2 Y, (Y = CH2, C(C6H5)2, Si(CH3)2, Si(C6H5)CH3, Sn(CH3)2 or Sn(C6H5)2) and a spiro compound [Fe(C5H4Se)2]2Sn have been prepared by reaction of ferrocene-1,1′-diselenol and halide complexes of the Group IV elements. Spectroscopic properties of the compounds are reported. In so...
The crystal structure of the title compound has been determined from 1 380 reflections measured by diffractometer. Crystals are orthorhombic, space group Pbca, with a= 10.811(3), b= 12.137(3), c= 15.233(4)Å, Z= 8. The structure was solved by direct methods and refined by least-squares to give R 0.041. The acid is present in the crystal in a non-pla...
The effect upon molecular packing of increasing chain length in a homologous series of mesogens has been examined in the case of the p-n-alkoxycinnamic acids by determination of the crystal structures of the four nematogenic acids having two, four, six, and eight carbon atoms in the alkyl chain. The chains have the all-trans extended conformation,...
A series of [3]ferrocenophanes with the symmetrical trichalcogen chains: Se3, SSeS, STeS, SeSSe, SeTeSe, as bridging groups has been synthesized. In solution these compounds are fluxional by a bridge-reversal process. The crystal structure of 1,3-dithia-2-selena-[3]ferrocenophane, which is isomorphous with that of the known 1,2,3-trithia-...
The conformation of 1,3,5-trithiane 1-oxide (3) observed in the crystal, as determined by single-crystal X-ray diffraction, has the sulfoxide oxygen axial. Previous studies involving proton and carbon nuclear magnetic resonance spectroscopy, as well as molecular mechanics calculations, indicated that the equatorial oxide is highly preferred in solu...
The molecular packing in p-hydroxy-cinnamic acid has been determined by single-crystal x-ray analysis in order to establish the role played by hydrogen bonding in inhibiting mesophase formation. The molecules exist in the crystal as centrosymmetric hydrogen-bonded dimers whose long axes are inclined at ± 84.7° to the crystal b-axis and lie almost i...
The crystal structures of two nematogens, p-[(p'-ethoxybenzylidene)aminolbenzonitrile (EOBABN) and p-[(p'-methoxybenzylidene)amino]phenyl acetate (MOBAPA), have been determined as part of a study of the relations between crystal structure and liquid crystallinity. In EOBABN the molecules are arranged in a head-to-tail fashion in rows parallel to th...
X-ray structure analyses have been carried out at room temperature for a crystalline modification of p-n-hexoxybenzoic acid (60BAC) which undergoes four solid-solid transitions on heating before yielding a nematic phase, and for a form of p-n-octoxybenzoic acid, different from that previously reported, which undergoes a single solid-solid transitio...
The isotypic crystal structures of three smectogenic p-n-alkoxybenzoic acids having eight, nine and ten carbon atoms in the alkyl chain are reported together with the crystal structure of a second modification of p-n-octoxybenzoic acid. The isotypic forms are identical in type to that previously reported for p-n-heptoxybenzoic acid (Bryan, Miller,...
The crystal structures of p-n-propoxy- and p-n-pentoxy-benzoic acids (3OBAC and 5OBAC) have been determined at room temperature by single-crystal x-ray analysis. Both crystals have sheet structures. Within each sheet the molecules are arranged as hydrogen-bonded dimers in head-to-tail fashion in parallel staggered rows. The long axes of the aromati...
The isotypic crystal form for the smectogenic p-n-alkoxybenzoic acids has been determined by room-temperature single-crystal x-ray diffraction analyses for the acids having 7, 8, 9, and 10 carbon atoms in the alkyl chain. The molecules are present in the crystals as centrosymmetric hydrogen-bonded dimers. The alkyl chains adopt an all-trans extende...
The lower melting 1,3-dioxide of 2,2-diphenyl-1,3-dithiane has been determined to be the cis diastereomer by 1H and 13C NMR spectroscopy and by single-crystal X-ray diffraction rather than trans as reported in the literature. The molecule exists in the conformation in the crystal which has both sulfoxide oxygens axial in spite of the significant el...
Condensation of 3-(lithiomethyl)pyridine with ethyl indole-2-carboxylate or the 1-methyl or 5-methoxy derivatives yields the corresponding substituted 2-indolyl (3-pyridyl)methyl ketone. Catalytic reduction, chloroacetylation, and ketalization with ethylene glycol yield the dioxolane derivatives of the corresponding substituted 2-indolyl [1-(chloro...
The crystal structure of the title compound (2) has been determined in order to establish the role of hydrogen-bond formation in inhibiting thermal mesomorphism. Hydrogen bonds link the molecules in the crystal in infinite interlocking zig-zag chains with the terminal hydroxy-groups acting as donors and the central nitrogen atoms as acceptors (O–H...
The crystal structures of 2-methyl-2-triphenylsilyl-1,3-dithiane (1) and trans-2-triphenylsilyl-1,3-dithiane 1-oxide (2) have been determined to establish their conformations and the effect upon ring geometry of a 2-triphenylsilyl substituent. Crystals of 1 conform to space group C2/c, with a = 28.780 (6), b = 11.901 (3), c = 15.909 (3) Å, β = 130....
1,3-Dithiane 1-oxide (1) has been resolved into its enantiomers by two methods, both based on separation of D(+)-camphor adducts followed by base-catalyzed cleavage back to 1 and camphor. Reaction of the lithio derivative of (±)-1 with D(+)-camphor gives a mixture of diastereomeric adducts 2 and 3, either of which may be isolated depending on the t...
The isolation and elucidation of the structure and stereochemistry of megaphone (1), a new cytotoxic neolignan from Aniba megaphylla Mez., are reported. Chemical and spectral evidence supported structure 1 for megaphone, and a direct x-ray crystallographic analysis confirmed the structure and established the stereochemistry. Two additional new cyto...
Single-crystal x-ray structure analyses have been carried out for trans-2-phenyl-1,3-dithiane 1-oxide (5), cis-2-phenyl-1,3-dithiane 1-oxide (6), and 2-phenyl-1,3-dithiane trans-1,trans-3-dioxide (7) to examine the effects of oxygen substitution on the geometry of the 1,3-dithiane ring. For 5, a = 12.206 (2), b = 5.749 (1), c = 14.809 (2) Å, β = 97...
Reduction of the carborane (CH3)4C4B8H8 with sodium in tetrahydrofuran produces the apparent (CH3)4C4B8H82- dianion, which in turn reacts with FeCl2 and NaC5H5 to generate a series of iron tetracarbon metallocarboranes. These include four isomers of a 14-vertex system, (η5-C5H5)2Fe2(CH 3)4C4B8H8, and one isomer of a nido 12-vertex species, (η5-C5H5...
The isolation and structural elucidation of elaeodendroside A (1), a novel cytotoxic cardiac glycoside containing a doubly linked sugar substituent, from Elaeodendron glaucum Pers. are reported.
The crystal structure of the tumor-inhibitory bisbenzylisoquinoline alkaloid tetrandrine has been determined by direct x-ray analysis. Crystals are orthorhombic, space group P212121, with a = 38.368 (6), b = 7.230 (2), c = 12.046 (2) Å, and Z = 4. All atoms, including hydrogen, were located and least-squares refinement gave R = 0.041 for 2633 nonze...
The isolation and elucidation of the structure and stereochemistry of an antileukemic macrocyclic diterpenoid, jatrophone (1), are reported. Mass spectrometry and elemental analysis supported a C 20H 24O 3 formula. Ketalization of 1 afforded ketal 3 which established the presence of a 2,3-dihydrofuran-3-one ring system in 1. On treatment with dry h...
A crystal structure analysis has been carried out on a sample of the lignan (–)-syringaresinol, C22H26O8, isolated from Tripterygium wilfordii. Crystals conform to space group P212121 with a= 13.051 (2), b= 18.106(4). c= 8.565(1)Å. and Z= 4. Intensities of 1 073 independent reflections were measured by counter diffractometry. The structure was solv...
The isolation spectral properties, and X-ray structure determination of gnidicoumarin(1), a novel pentacyclic dicoumarin, are reported.
Zusammenfassung Nachweis, dass Podolid, ein neues antileukämisches norditerpinisches Dilacton ausPodocarpus gracilior Pilg. die Struktur (1) besitzt.
The crystal structure of podolide, (I), C19H22O5, an antileukemic norditerpene dilactone isolated from Podocarpus gracilior, has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21, with a= 12.165(3), b= 7.771(1), c= 9.708(4)Å, β= 113.76(3)°, and Z= 2. The structure was solved by direct methods and refined by leas...
The crystal structure of the title compound has been determined from 1951 diffractometer data. Crystals are triclinic, a= 7.744(1), b= 10.676(2), c= 14.278(2)Å, α= 95.54(2), β= 108.42(1), γ= 102.63(1)°, space group P1, Z= 4. The structure was solved by Patterson methods, and refined by least-squares methods to R0.050. The molecules form hydrogen-bo...
The crystal structure of the title compound has been determined from 740 reflections measured by diffractometer. Crystals are monoclinic, a = 27.148(4), b = 4.013(1), c = 21.787(3) Å, β = 135.97(1)°, space group C2/c, Z = 8. The structure was solved by a fit of the weighted reciprocal lattice to the calculated Fourier transform for the molecule, an...
p-Methoxycinnamic acid (I) is nematogenic but cinnamic acid (II), although as a hydrogen-bonded dimer it has the necessary molecular anisotropy, is not. The crystal structures of the two compounds have been determined at room temperature, and this difference can be directly attributed to differences in molecular packing. Crystals of (II) are monocl...
The isolation and structural elucidation of a new antileukemic iridoid lactone, allamandin (1), and the new companion iridoids, allamandicin (3) and allamdin (4), are reported. Elemental analysis and mass spectrometry established a C15H16O7 molecular formula for allamandin (1), and the structure was established by spectral studies and dehydration t...
Complexes of a series of imidazoles including imidazole, 1-methylimidazole, 4-methylimidazole, 4,5-dimethylimidazole, and benzimidazole with pentaammineruthenium in the II and III oxidation states are described. Except for 4,5-dimethylimidazole, good yields of complexes having imidazole bound to ruthenium through the N-3 nitrogen are obtained by re...
The title compound crystallizes in the triclinic space group P, with Z= 2 in a unit cell with a= 10·557(1), b= 10·043(1), c= 11·230(1)Å, α= 114·22(1), β= 91·95(1), γ= 92·25(1)°. The structure was solved by the heavy-atom method, from 3217 independent reflections measured by counter diffractometry. Refinement by least-squares methods gave R 0·024.To...
Papaverin (I) wird bei der Oxidation mit VOF3 in Trifluoressigsäure intermolekular zu dem Bis-Molekül (II) gekuppelt, (i)-Laudanosin (IIIa) dagegen durch intramolekulare Kupplung zu (i)-Glaucin (IVa) cyclisiert.
The molecular structure and absolute configuration of datiscoside (Ia) have been determined from a three-dimensional, single-crystal. X-ray analysis of its bis-(p-iodobenzoate) dihydrate (Ib). Crystals have orthorhombic symmetry, space group P212121, with a = 19.609(7),b = 31.485(17),c = 8.743(3) Å, Z = 4. The structure was solved by the heavy-atom...
The molecular structure and absolute configuration of maytansine (Ia) have been found from a three-dimensional single-crystal X-ray analysis of its (3-bromopropyl) ether (Ib). Crystals are orthorhombic, space group P212121 with a= 24·239(4), b= 16·044(4), c= 10·415(2)Å, and Z= 4. The structure was solved by the heavy-atom method and refined by Four...
The crystal and molecular structures and absolute configuration of the title compounds, have been determined by three-dimensional, single-crystal, X-ray analysis. Crystals of triptolide (Ia) are monoclinic, space group P21, with a= 13·420(1), b= 6·256(1), c= 11·593(1)Å, β= 118·09(1)°, and Z= 2. Crystals of tripdiolide (Ib) have the same space group...
The isolation and structural elucidation of liatrin, a novel sesquiterpene lactone from Liatris chapmanii, are reported. Liatrin has significant antileukemic activity in mice and possesses the unusual germacranolide cis,cis-diene structure 1. Reduction of liatrin with sodium borohydride gave the diol 5, which was converted to a crystalline mono-o-b...
A three-dimensional, single-crystal, X-ray analysis of the title compound has confirmed its molecular structure and absolute configuration, and thus the stereochemistry and absolute configurations of the related alkaloids, zygadenine, germine, and protoverine. Crystals are monoclinic, a= 20·484(3), b= 8·828(1), c= 25·208(4)Å, β= 114·55(1)°, space g...
The isolation and structural elucidation of eriolangin (1) and eriolanin (2), novel antileukaemic 1,10-seco-eudesmanolides from Eriophyllum lanatum, are reported.
Die Reaktion von Trimethylgallium bzw. -indium mit 2,3-Dicarba-nido-hexaboran(8) führt zu den geschlossenen Polyedern (I) (30 bzw. 60% Ausbeute), in denen das Metallatom eine Spitze der pentagonalen Bipyramide besetzt.
The reaction of trimethylgallium or trimethylindium with 2,3-dicarba-nido-hexaborane(8) yields the closed polyhedral species 1-CH3GaC2B4H6 and 1-CH3InC2B4H6, respectively, in which the metal atom in each case forms one apex of a pentagonal-bipyramidal cage. These carboranes have been structurally characterized by boron-11 and proton nmr, mass spect...
Citations
... An uncharacterized CoA ligase transforms dicarboxylic acid into its CoA form to be utilized by Tri3 and Tri18 to afford the acylated product 54. Importantly, 55 also serves as the key precursor of many other acylated trichothecenes with diverse side chains, including crotocin (56) [59], baccharin (baccharinoid B5) (57) [60], roridin A (58) [61], and satratoxin H (39) [62] (Fig. 5C). ...
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... Parallel to the development of cyclopentadiene sandwiched triple-layer complexes, Grimes synthesized the first neutral triple-layer cobalt complexes with the carboranyl ring C 2 B 3 H 5 bridging the two CoCp moieties [44]. Since then, this group has characterized a series of triple-layer metallacarborane sandwiches containing transition metal atoms [4,5,[45][46][47][48]. The structure, reactivity and electrochemistry of closely related diborolene complexes, which contain C 3 B 2 rings, were studied by Siebert's group [49 -52]. ...
... Trichalcogenaferrocenophanes are a useful class of compounds for studying the trend in the SBI strengths of the group 16 elements (see Chart 1). While [FeIJC 5 H 4 E) 2 E′] (E, E′ = S, Se, Te) complexes have been known for a long time, crystal structures have been reported for only [Fe(C 5 H 4 S) 2 S] (1), 10 [Fe(C 5 H 4 S) 2 Se] (2), 11 [Fe(C 5 H 4 Se) 2 Se] (the monoclinic polymorph 5a and the orthorhombic polymorph 5b), 12 [Fe(C 5 H 4 Te) 2 Se] (8), 13 and [Fe(C 5 H 4 Te) 2 Te] (9). 14 Structures of some related complexes in which the cyclopentadienyl rings of ferrocene have been modified are also known. ...
... With the aim of developing new series of ferrocene-based phosphine organocatalysts, a few years ago we targeted 2phospha [3]ferrocenophanes as potentially suitable scaffolds [5,6]. We demonstrated that the planar chiral (S,S)-2-phospha [3]ferrocenophanes 1, called FerroPHANEs (Scheme 1), are highly efficient and robust nucleophilic organocatalysts for enantioselective cyclizations [7]. ...
... This is similar to the situation in the complex (Ph 3 Sb)Fe(CO) 4 , in which the Fe-CO bond trans to SbPh 3 is significantly shorter than the others (2.904 Å vs 2.924e2.936 Å) [5], and is indicative that 2 has a stronger trans influence than SbPh 3 and comparable to that of CO and a bridging SbPh 2 [6]. Although the solid-state structure of 3 shows that the ligand 2 occupies an axial position in the coordination sphere of the Fe atom (labeled as axial isomer), fast equilibration in solution between the axial and equatorial isomers is expected for such trigonal bipyramidal structures. ...
... CO2H, NO2, OH and C2HnNO, are also listed in Table 2. The crystal structure of the title compound is similar to other phenyl-ring-based structures (Bryan, Hartley, Peckler, Fujita, Nagao & Seno, 1980;Bums & Hagaman, 1993;Carpy, Goursolle & Leger, 1980;Gozlan & Riche, 1976;Kageyama, Iwamoto, Haisa & Kashino, 1993;Metzger, Laidlaw, Torres & Panetta, 1989;Metzger, Atwood, Lee, Rao, Lal & Loo, 1993;Nielsen & Larsen, 1993;Okabe, 1993;Okabe, Nakamura & Fukuda, 1993;Soundararajan, Duesler & Hageman, 1993). ...
... Une analyse d6taill6e des documents bibliographiques (Benedetti, Ganis, Bombieri, Caglioti & Germain, 1975;Bryan & Shen, 1978;Destro & Colombo, 1979;Harlow & Simonsen, 1976;Jeffrey, Rosenstein & Vlasse, 1967;Kok, De Clercq, Vandewalle, Declercq, Germain & Van Meerssche, 1979;Thiessen & Hope, 1970) montre que le cycle lactonique 0567-7408/81/101930-03501.00 se pr6sente g6n6ralement sous une conformation enveloppe, les atomes du groupement ester (C-O-CO-C) 6tant coplanaires; suivant la nature des substituants, l'angle* de plissement du cycle varie de 20 /l 60 °. ...
Reference: Phénoxy-2 γ-butyrolactone
... 1,10-secoeudesmanolide isolated from Eriophyllum lanatum Forbes (Compositae) by Kupchan, Baxter, Chiang, Gilmore & Bryan (1973). Structural elucidation of eriolanin was by a combination of spectral and X-ray diffraction studies, the latter work performed by Bryan & Gilmore (1975). They studied a mixed crystal of dehydroeriolanin (DE, *Present address: National Research Council of Canada, Department of Biological Sciences, Ottawa, Ontario, Canada K 1A 0RA. ...
Reference: (±)-6-epi-Eriolanin
... The dimensions of the coumarin nucleus in this molecule are in agreement with those found in a number of other systems (Valente, Trager & Jensen, 1975;Shimizu, Kashino & Haisa, 1975;Shen & Bryan, 1975;Boles, Taylor & Girven, 1975;Fayos, 1976). The C(17)-C(18) bond is, however, relatively short, 1.326 A. Some of this shortening may be caused by thermal motion, which is found to be relatively pronounced for these two atoms. ...
... The crude extract was also active against these bacteria, thereby supporting the notion of the chemical defense efficacies of these seed-borne compounds. The DPPH free radical scavenging properties of the isolated compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) were evaluated. The isolated compounds showed weak properties compared to the reference standard, Trolox (Table 5). ...
