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Dale C Swenson

Publications and source records attributed to Dale C Swenson.

18 recordsLinked to original sources
PubMed2006

Heliconols A-C: antimicrobial hemiketals from the freshwater aquatic fungus Helicodendron giganteum.

[Structure: see text] Cultures of the freshwater aquatic fungus Helicodendron giganteum afforded three new compounds, heliconols A-C (1-3), that contain an unusual reduced furanocyclopentane unit. The structures of these metabolites were assigned by analysis of 1D and 2D NMR data. The absolute configuration of heliconol A (1) was assigned by single-crystal X-ray crystallographic analysis of its dibromobenzoate derivative. Heliconol A showed antifungal and antibacterial activities in disk diffusion assays.

Anti-Bacterial Agents↗
PubMed2006

Penifulvin A: a sesquiterpenoid-derived metabolite containing a novel dioxa[5,5,5,6]fenestrane ring system from a fungicolous isolate of Penicillium griseofulvum.

[structure: see text] Penifulvin A (1), a new fungal metabolite with a previously undescribed ring system, has been isolated from cultures of an isolate of Penicillium griseofulvum (NRRL 35584) obtained from a white mycelial growth on a dead hardwood branch collected in a Hawaiian forest. The structure was assigned by analysis of NMR data and confirmed by single-crystal X-ray diffraction analysis. Penifulvin A (1) shows significant activity in dietary assays against the fall armyworm Spodoptera frugiperda.

Animals↗
PubMed2006

Caryophyllene sesquiterpenoids from a fungicolous isolate of Pestalotiopsis disseminata.

Three new caryophyllene-type sesquiterpene alcohols, 6-hydroxypunctaporonin E (1), 6-hydroxypunctaporonin B (2), and 6-hydroxypunctaporonin A (3), have been isolated from cultures of the fungicolous fungus Pestalotiopsis disseminata. The structures of 1-3 were determined mainly by analysis of 1D and 2D NMR data. The structure and absolute configuration of 6-hydroxypunctaporonin E (1) was confirmed through X-ray crystallographic analysis of its mono-bromobenzoate derivative. Compounds 1 and 2 showed activity against Gram-positive bacteria.

Ascomycota↗
PubMed2006

Chloriolide, a 12-membered macrolide from Chloridium virescens var. chlamydosporum (NRRL 37636).

A new 12-membered macrolide (chloriolide; 1) was obtained from solid-substrate fermentation cultures of Chloridium virescens var. chlamydosporum that was originally isolated from decayed wood. The structure of 1 was determined by analysis of 1D NMR, 2D NMR, and MS data and confirmed by X-ray crystallographic analysis. The absolute configuration of 1 was assigned by application of the modified Mosher method using the (R)- and (S)-MTPA derivatives of a rearrangement product obtained under standard acylation conditions. The assignment made by analysis of the corresponding Deltadelta values was verified by X-ray crystallographic analysis of the (S)-MTPA derivative.

Ascomycota↗
PubMed2006

Decaspirones A-E, bioactive spirodioxynaphthalenes from the freshwater aquatic fungus Decaisnella thyridioides.

Decaspirones A-E (1-5), five new compounds related to the palmarumycins, were isolated from cultures of the freshwater aquatic fungal species Decaisnella thyridioides. The known compound palmarumycin CP1 (6) was also obtained. The structures of 1-5 were determined by analysis of NMR and MS data, and their relative configurations were assigned by analysis of 1H NMR J-values and NOESY data. The structure of the lead compound 1 was confirmed by X-ray crystallographic analysis. Compounds 1-5 possess a trans ring fusion not previously reported in members of this structural class. The absolute configuration of 1 was assigned using the modified Mosher method. Compounds 1-5 showed potent antifungal and antibacterial activity.

Anti-Bacterial Agents↗
PubMed2005

Malettinins B-D: new polyketide metabolites from an unidentified fungal colonist of Hypoxylon Stromata (NRRL 29110).

Malettinins B-D (2-4), three new antimicrobial polyketide-derived metabolites related to the previously reported malettinin A (1), have been obtained from nonsporulating cultures of an isolate of Mycelia sterilia MYC-155 (= NRRL 29110) collected from colonies of Hypoxylon stromata. Malettinins B (2) and C (3) are partially reduced analogues of malettinin A and were identified by analysis of NMR and MS data. Malettinin D (4) is biogenetically similar, but possesses a new ring system, and the structure of 4 was established by single-crystal X-ray diffraction analysis.

Agaricales↗
PubMed2004

Synthesis and structure of 2,5,8-triazido-s-heptazine: an energetic and luminescent precursor to nitrogen-rich carbon nitrides.

Derivatized s-triazine (C3N3) precursors have seen significant recent use in the production of carbon nitride materials. Larger polycyclic molecular precursors, such as those containing an s-heptazine core (C6N7 or tri-s-triazine), may improve stability and order in carbon nitride products. In this Communication, we describe the synthesis and crystal structure of 2,5,8-triazido-s-heptazine (2). Synthesis of 2 was achieved from melon, an oligomeric s-heptazine synthesized by the pyrolysis of NH4SCN. Melon was converted to molecular 2,5,8-trichloro-s-heptazine, which was then transformed to the triazide upon reaction with (CH3)3SiN3. The crystal structure of 2 verifies that the s-heptazine is planar and the azides adopt a pinwheel-like C3h arrangement around the periphery. The s-heptazine core shows pi delocalization in the C-N bonds around the periphery (av. 1.33 A), while the internal planar C-N bonds are longer (1.40 A). The heptazine units pack into parallel, but offset, layered sheets in the crystal. The triazide 2 exhibits photoluminescence at 430 nm and rapidly and exothermically decomposes upon heating at 185 degrees C to produce a tan thermally stable carbon nitride powder with a formula near C3N4.

Journal Article↗
PubMed2003

Novel antiinsectan oxalicine alkaloids from two undescribed fungicolous Penicillium spp.

15-Deoxyoxalicine B (1) and decaturins A (2) and B (3) have been isolated from Penicillium decaturense and Penicillium thiersii, two previously undescribed species obtained as colonists of wood-decay fungi. The structures were determined by 2D NMR experiments and/or single-crystal X-ray diffraction analysis. These compounds are members of a rare structural class, and decaturins A and B feature a new polycyclic ring system. Decaturin B (3) exhibited potent antiinsectan activity against the fall armyworm (Spodoptera frugiperda).

Alkaloids↗
PubMed2003

A planar tetracoordinate carbon and unusual bonding in an organodimetallic propynylidene complex arising from double C-H activation of an allene ligand.

Reduction of the organoditantalum allene complex (eta-C5Me4R)2Ta2(mu-X)X3(mu-eta1,eta3-C3H4) (R = Me (Cp*), Et; X = Cl, Br) with sodium amalgam leads to the propynylidene complex (eta-C5Me4R)2Ta2(mu-H)2X2(mu-HCCCH) by a formal double 1,3-C-H activation of the allene ligand. The solid-state molecular structure contains a planar HCCCH ligand bridging, in parallel coordination mode, the two tantalum atoms, with the HCCCH and Ta atoms coplanar. Key structural features are a Ta-Ta distance of 2.8817(7) A, propynylidene C-C-C angle of 153.7(13) degrees , C-C distance of 1.370(8) A, Ta-C(central) distance of 2.194(9) A, and Ta-C(terminal) distance of 1.970(9) A. Molecular orbital calculations on the complex at the RHF/SBK(d) and B3LYP/LanL2dz levels of theory demonstrate that the propynylidene ligand is best viewed formally as an allenediylidene(4-) ligand bonded to two d0 tantalum atoms via two Ta=C(terminal) double bonds and an unusual three-center, two-electron bridge bond involving both tantalum atoms and a lone pair on the planar, tetracoordinate central carbon. There is no net Ta-Ta bonding based on the orbital analysis.

Journal Article↗
PubMed2003

New bioactive rosigenin analogues and aromatic polyketide metabolites from the freshwater aquatic fungus Massarina tunicata.

Four new rosigenin analogues (massarigenins A-D; 1-4) and two new aromatic polyketide-derived secondary metabolites (massarinins A and B; 6, 7) and have been isolated from the freshwater aquatic fungus Massarina tunicata. The structures of these compounds were determined primarily by analysis of NMR data, and that of compound 1 was verified by X-ray crystallography. The known compound 4-(2-hydroxybutynoxy)benzoic acid (11) was also obtained, and its absolute stereochemistry was assigned. Several of these metabolites showed antibiotic activity against Gram-positive bacteria.

Ascomycota↗
PubMed2003

Lowdenic acid: a new antifungal polyketide-derived metabolite from a new fungicolous Verticillium sp.

Lowdenic acid (1), a new antifungal metabolite with an unusual structure and a mixed biogenetic origin, has been obtained from nonsporulating cultures of a previously undescribed Verticillium sp. (MYC-406 = NRRL 29280) that was isolated as a colonist of polypore basidiomata. The gross structure of 1 was proposed by analysis of NMR data and confirmed by X-ray diffraction analysis, which enabled assignment of relative stereochemistry. Compound 1 occurs as an equilibrium E/Z mixture. The known antifungal metabolite canescin A (2) was also isolated.

Antifungal Agents↗
PubMed2002

Gallium and gallium dichloride, new solid-state reductants in preparative transition metal chemistry. New, lower temperature syntheses and convenient isolation of hexatantalum tetradecachloride octahydrate, Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O, and synthesis and solid-state structure of a tetraalkylammonium derivative, [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)], of the reduced [Ta(6)(mu-Cl)(12)](2+) cluster core(1).

Reduction of TaCl(5) with either Ga or Ga(2)Cl(4), in the presence of NaCl, in a sealed borosilicate glass ampule at 500 degrees C, followed by aqueous Soxhlet extraction and treatment with SnCl(2) and hydrochloric acid, yielded Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O in 92% (Ga) or 96% (Ga(2)Cl(4)) yield. Ga(2)Cl(4), a probable intermediate in the Ga-based reduction, is a more convenient reductant than Ga because it is readily dispersed in the reaction mixture, and these mixtures do not require homogenizations in order to afford high yields. Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O was converted by ligand exchange to the first tetraalkylammonium derivative, [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)], of the reduced cluster core Ta(6)(mu-Cl)(12)(2+), in 88% yield. [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)] crystallizes from 1,2-dichloroethane/toluene mixtures in two crystalline morphologies, a nonsolvated cubic form and a solvated needle form. The solid-state molecular structures of both crystalline morphologies of [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)] consist of octahedral, 16 VEC hexatantalum cluster anions with an average Ta-Ta distance of 2.900[2] A, a Ta-Cl(bridge) distance of 2.463[2] A, a Ta-Cl(terminal) distance of 2.567[5] A, and a Ta-Cl-Ta angle of 72.1[1] degrees for the cubic form, and for the solvated needle morphology, an average Ta-Ta distance of 2.900[1] A, a Ta-Cl(bridge) distance of 2.461[1]A, a Ta-Cl(terminal) distance of 2.567[3] A, and a Ta-Cl-Ta angle of 72.19[7] degrees.

Chemistry, Inorganic↗
PubMed2002

Synthesis and characterization of an air-stable gallium hydride, [t-Bu(H)Ga(mu-NEt(2))](2), and related chloride derivatives.

The synthesis of [t-Bu(H)Ga(mu-NEt(2))](2) (1) was accomplished by the addition of 4 t-BuLi to [Cl(2)Ga(mu-NEt(2))](2). Evidence suggests that two tert-butyl groups are lost as isobutylene and result in Ga-H bond formation. The gallium hydride 1 is remarkably stable toward ambient air, oxygen, photolysis, and moderate heating; however, in CHCl(3) the hydride is replaced by chloride, producing [t-Bu(Cl)Ga(mu-NEt(2))](2) (2). Compound 1 may also be synthesized by sequential tert-butyl additions to [Cl(2)Ga(mu-NEt(2))](2). A singly substituted tert-butyl dimer, t-Bu(Cl)Ga(mu-NEt(2))(2)GaCl(2) (3), was also isolated, and interconversions between 1, 2, and 3 are described. Compound 1 was tested for utility in the chemical vapor deposition of GaN and produced gallium-rich films at low temperatures (<250 degrees C) with limited nitrogen incorporation due to facile Et(2)NH elimination.

Journal Article↗
PubMed2002

(+-)-Tartaric acid.

(+-)-Tartaric acid, C(4)H(6)O(6), crystallized from ethanol in space group P 1 macro. The structure is characterized by five hydrogen bonds, including the formation of a centrosymmetric carboxylic acid dimer which forms infinite chains along the body diagonal. These chains form sheets via hydrogen bonding between alpha-hydroxyl groups. The sheets are connected through a bifurcated hydrogen bond. Structural comparisons are made with homochiral (2R,3R)-(+)-tartaric acid.

Journal Article↗