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1.
Six 20,24-dimethylscalarane derivatives (, , , , , and ) have been isolated from the Neo Guinean sponge Carteriospongia foliascens. Compound is identical with a C27 tetracyclic terpene previously isolated from an Australian specimen of the same sponge. The five other derivatives are new and their structures have been established on the basis of their spectral data. The structure of was confirmed by single-crystal X-ray diffraction and that of by chemical correlation with . The configuration at C-4 for all these compounds has been determined through 13C NMR data. Evidence leading to reverse the configuration at this centre in previously reported C27 tetracyclic terpenes is discussed. An ecological function is suggested for these molecules. 相似文献
2.
Aldehydes and ketones add to the cycloheptatriene ester anion and to the carboxylic acid dianion at C-7 (α-attack) or C-2 (C-5) (γ-attack), depending on the starting compounds. 相似文献
3.
Three new high molecular weight bromotyrosine-related metabolites, , and , were isolated from the sponge Aplysina ( Verongia) fistularis forma fulva, and their structures were determined from high resolution 1H NMR and other spectroscopic data. The new metabolites are formally derived by combination of major segments of two known Aplysina metabolites and . 相似文献
4.
The major metabolite of Chromodoris marislae, marislin () was identified from spectral data and converted into the sponge metabolite pleraplysillin-2 (). 相似文献
5.
The N-hydroxyazetidines and are prepared startinfrom 2,3-dihydroazete 1-oxides ( and 0 by reduction with sodium borohydride and by reaction with a nucleophile, respectively. The N-thydroxyazetidines and can be oxidized with mercury (II) oxide to the corresponding nitrones ; oxidation of the N-hydroxyazetidine (unsubstituted at C-4) with equivalent of lead tetraacetate tyields the N-tacetoxy β-lactam . 相似文献
6.
The model tripeptide Boc-Gly-S-Ala-Aib-OMe () and the two monothiated analogues Boc-Gly(1ψ2CSNH)-S-Ala-Aib-OMe () and Boc-Gly-S-Ala(2ψ3 CSNH)-Aib-OMe () were synthesized. Peptide was obtained by thiation of using 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, Lawesson's Reagent (LR), followed by deprotection of the Boc group and coupling with Boc-Gly-OH. Thiation of with LR regiospecifically transformed the protected tripeptide to the monothiated analogue . X-Ray diffraction analysis showed that the type-III β-turn formed by the reference peptide is preserved in the monothiated analogue ; conversely,the structure of the isomeric tripeptide is partially extended. 相似文献
7.
The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid (, ; ; , ) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-,,, (R)(–)-). 相似文献
8.
Swinholide-A (a) a novel 22-membered macrolide has been isolated from a Red Sea sponge. The structure of the tetraformate () has been determined on basis of spectral data using 2D-NMR correlations. 相似文献
9.
Ronald J. Quiann Richard P. Gregson Alan F. Cook Robert T. Bartlett 《Tetrahedron letters》1980,21(6):567-568
A new pharmacologically active agent isolated from the marine sponge has been identified as 1-methylisoguanosine () by spectral and degradative chemical methods and synthesis from a β-D-ribofuranosylimidazole (). 相似文献
10.
Two novel nucleosides, mycalisines A and B, have been isolated from a marine sponge and their structures elucidated as 4-amino-5-cyano-7-(3--methyl-5-deoxy-β-D--pent-4-enofuranosyl)-pyrrolo[2,3-]pyrimidine and 5-cyano-7-(3--methyl-5-deoxy-β-D--pent-4-enofuranosyl)-pyrrolo[2,3-]pyrimidine-4-one, respectively. Both compounds inhibit cell division of fertilized starfish eggs. 相似文献
11.
The structure of manoalide (), a new sesterterpenoid antibiotic isolated from a marine sponge, has been determined by spectral analysis and chemical transformations. 相似文献
12.
From the marine sponge a novel degraded C19 terpene diacetate () has been isolated and its structure elucidated by spectral analysis, including 2D-NMR, and chemical evidence. 相似文献
13.
The LiPO3CeP3O9 and NaPO3CeP3O9 systems have been investigated for the first time by DTA, X-ray diffraction, and infrared spectroscopy. Each system forms a single 1:1 compound. LiCe(PO3)4 melts in a peritectic reaction at 980°C. NaCe(PO3)4 melts incongruently, too, at 865°C. These compounds have a monoclinic unit cell with the parameters: a = 16.415(6), b = 7,042(6), c = 9.772(7)Å; β = 126.03(5)°; Z = 4; space group for LiCe (PO3)4; and a = 9.981(4), b = 13.129(6), c = 7.226(5) Å, β = 89.93(4)°, Z = 4, space group for NaCe(PO3)4. It is established that both compounds are mixed polyphosphates with chain structure of the type |MIIMIIIII (PO3)4|∞MII: alkali metal, MIIIII: rare earth. 相似文献
14.
《Tetrahedron》1987,43(15):3471-3480
Biologically inactive but easily available chaparrin has been converted into potent antileukemic C-15 esters of glaucarubolone and quassinoid analogs in which the C-15 ester side chain has been replaced by an alkyl or alkenyl group.The synthetic methodology developed has been applied to the preparation of C-15 ester derivatives , , and quassinoid analogs , and . 相似文献
15.
Hideshi Nakamura Houming Wu Junichi Kobayashi Yoichi Nakamura Yasushi Ohizumi Yoshimasa Hirata 《Tetrahedron letters》1985,26(37):4517-4520
Purealin , a novel secondary metabolite, which modurates enzymic reactions of ATPases, has been isolated from the okinawan marine sponge and the structure has been determined by the 1H-1H homonuclear and 1H-13C heteronuclear NMR chemical shift correlations and CD spectra. 相似文献
16.
The crystal structure of NbS3 was determined from single-crystal diffractometer data obtained with MoKα radiation. The compound is triclinic, space group , with: a 4.963(2) Å; b = 6.730(2) Å; c = 9.144(4)Å; α = 90°; β = 97.17(1)°; γ = 90°. The structure is closely related to the ZrSe3 structure type; it shows that the compound can be formulated as Nb4+(S2)2?S2?, in agreement with XPS spectra. The main difference with ZrSe3 is that the Nb atoms are shifted from the mirror planes of the surrounding bicapped trigonal prisms of sulfur atoms to form NbNb pairs (NbNb = 3.04 Å); this causes a doubling of the b axis relative to ZrSe3 and a decrease of the symmetry to triclinic. 相似文献
17.
A brominated bisacetylenic acid, 18-bromooctadeca-9(E), 17(E)-dien-7, 15-diynoic acid, has been isolated from the marine sponge and its structure elucidated by NMR including 2D homonuclear spectroscopy. 相似文献
18.
Michele DAmbrosio Antonio Guerriero Pietro Traldi Francesco Pietra 《Tetrahedron letters》1982,23(42):4403-4406
Cavernicolin-1 and Cavernicolin-2, two epimeric compounds having a γ-lactam ring fused to a dibromocyclohexenone ring, have been isolated from the Mediterranean sponge . 相似文献
19.
Isomerization of -bicyclo[10.8.0]eicos-1(12)-ene () and -bicyclo[10.10.0]docos-1(12)-ene () to [10.8]- and [10.10]betweenanene ( and ) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 / and 95/5> /). 相似文献
20.
Pier L. Bellon Francesco Demartin Vladimiro Scatturin Bronislaw Czech 《Journal of organometallic chemistry》1984,265(1):65-71
The meso-diastereoisomer of 1,12-dimethyl-2,11-dithia-5,8-dioxa[12](1,1′)ferrocenophane crystallizes in space group P with a 8.879(2), b 10.135(2), c 12.030(2) Å, α 100.14(1), β 99.02(1), γ 103.93(1)°; the ferrocenyl moiety has an eclipsed conformation and the bridging chain a steric arrangement of the type aag+aag?g+aag?a. 相似文献