- Phorbasins G-I: Three new diterpenoids from the sponge Phorbas gukulensis
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Phorbasins G-I (1-3) were isolated from the sponge Phorbas gukulensis collected from Gagu-Do, Korea. The complete structure of the compounds was determined by NMR and MS spectroscopy, along with chemical reaction. Phorbasin G (1) was found to be a diterpene possessing a taurine residue.
- Lee, Hyi-Seung,Park, Su Young,Sim, Chung Ja,Rho, Jung-Rae
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- Stellettazole D, a cytotoxic imidazole alkaloid from the marine sponge Jaspis duoaster
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A new cytotoxic imidazole alkaloid, stellettazole D, containing norsesquiterpene and aminopropylimidazolium units, has been isolated from the marine sponge Jaspis duoaster. The structure of stellettazole D was assigned on the basis of NMR, mass spectrometry, and IR spectral data. Stellettazole D has moderate cytotoxicity against a limited number of tumor cells.
- Sato, Seizo,Iwata, Fumie,Takeo, Jiro,Kawahara, Hiroyuki,Kuramoto, Makoto,Uno, Hidemitsu
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- Cytotoxic pyrrolo- and furanoterpenoids from the sponge Sarcotragus species
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Reexamination of the configuration of sarcotins A-C, first isolated from the marine sponge Sarcotragus sp., revealed that the proposed stereochemistry of the tetronic acid moiety needs to be revised as shown in 1-3. Additional new pyrrolosesterterpenes (5-11), furanosesterpene derivatives (4, 12-14, 19), and furanoterpenoids, including two trinorsesterterpenes (15, 16) and two diterpenes (17, 18), were isolated from the same sponge by bioactivity-guided fractionation. The planar structures were established on the basis of NMR and MS analysis. The stereochemistry was defined by combined use of NMR, CD spectroscopy, and chemical degradation. The compounds were evaluated for cytotoxicity against five human tumor cell lines and were found to exhibit moderate to significant activity.
- Liu, Yonghong,Hong, Jongki,Lee, Chong-O.,Im, Kwang Sik,Kim, Nam Deuk,Choi, Jae Sue,Jung, Jee H.
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- First Direct Synthesis of Optically Active 3-Methylcyclopentene
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(-)-(S)- and (+)-(R)-3-methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis.The (S)-configuration for (-)-1 was confirmed by correlation with (-)-(S)-1-methylindane.
- Sliwka, Hans-Richard,Hansen, Hans-Juergen
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- Asymmetric hydrodimerization of styrene by a chiral zirconium complex containing a tetradentate [OSSO]-type bis(phenolato) ligand
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The chiral non racemic (Λ,R,R)-[OSSO]Zr(CH2Ph) 2 (1a) activated by methylaluminoxane (MAO) and in presence of H 2 produces the chiral hydrodimer (S)-1,3-diphenylbutane with good selectivity respect to the achiral 1,4-diphenylbutane. The absolute configuration of the chiral dimer and the effect of the hydrogen pressure on the ratio between 1,3-diphenylbutane and 1,4-diphenylbutane give useful information about the regiochemistry and stereochemistry of insertion of the styrene into the Zr-H bond.
- Galdi, Nunzia,Santoro, Orlando,Oliva, Leone,Proto, Antonio,Capacchione, Carmine
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scheme or table
p. 1113 - 1117
(2012/02/03)
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- Enantioselective and diastereoselective Mukaiyama-Michael reactions catalyzed by bis(oxazoline) copper(II) complexes
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The scope of highly enantioselective and diastereoselective Michael additions of enolsilanes to unsaturated imide derivatives has been developed with use of [Cu((S,S)-t-Bu-box)](SbF6)2 (1a) as a Lewis acid catalyst. The products of t
- Evans,Scheidt,Johnston,Willis
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p. 4480 - 4491
(2007/10/03)
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