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Lee, Ji-Hye,Lee, Taek-Kyun,Kang, Rae-Seon,Shin, Hee-Jae,Lee, Hyi-Seung Korean Magnetic Resonance Society 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.1
A series of bromophenols and corresponding debrominated phenolic compounds was prepared by isolation from red alga Tichocarpus crinitus and by structural modification of natural bromophenols. Their structures were determined by extensive NMR analysis and the antioxidant activities were established through the determination of their abilities to inhibit free radicals using DPPH as the stable radical. The most active free radical scavengers were the debrominated phenolic derivatives 3,4-dihydroxybenzyl alcohol and 3,3',4,4'-tetrahydroxydiphenylmethane.
Nortriterpene glycosides of the sarasinoside class from the sponge Lipastrotethya sp.
Lee, Jung-Ho,Jeon, Ju-eun,Lee, Yeon-Ju,Lee, Hyi-Seung,Sim, Chung J,Oh, Ki-Bong,Shin, Jongheon American Society of Pharmacognosy ; American Chemi 2012 Journal of natural products Vol.75 No.7
<P>Five new nortriterpene glycosides, along with eight known compounds of the sarasinoside class, were isolated from the tropical sponge Lipastrotethya sp. collected from Chuuk, Micronesia. The structures of these new compounds, designated as sarasinosides N-R (9-13), were determined by combined spectroscopic and chemical methods. The aglycone portions of 10-13 were found to be unprecedented among nortriterpeneoids on the basis of extensive NMR analyses. Several of these compounds exhibited cytotoxicity against A549 and K562 cell lines as well as weak inhibitory activity against Na(+)/K(+)-ATPase.</P>
Lee, Jong-Seok,Kim, Byung-Sook,Shin, Jun-Ho,Lee, Yeon-Ju,Shin, Hee-Jae,Lee, Hyi-Seung Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
A novel and efficient tetrahydrofuranyl ring opening method was developed using the highly reactive TFAT reagent in the presence of an acid scavenger, 2,6-di-tert-butyl-4-methylpyridine. Various acid sensitive groups are compatible with the reaction condition, making it generally applicable to many tetrahydrofuranyl steroids. Moreover, it is a synthetic equivalent of 'Marker degradation' affording an efficient synthesis of C17-OH rockogenin acetate.
Total Synthesis and Configurational Validation of (+)‐Violapyrone C
Lee, Jong Seok,Shin, Junho,Shin, Hee Jae,Lee, Hwa‐,Sun,Lee, Yeon‐,Ju,Lee, Hyi‐,Seung,Won, Hoshik WILEY‐VCH Verlag 2014 EUROPEAN JOURNAL OF ORGANIC CHEMISTRY Vol.2014 No.21
<P><B>Abstract</B></P><P>Gold(I)‐catalyzed intramolecular 6‐<I>endo</I>‐<I>dig</I> cyclization of <I>tert</I>‐butyl ynoates afforded α‐pyrone cores of violapyrones. Moreover, this reaction was successfully applied to the stereospecific syntheses of (+)‐ and (–)‐violapyrone C, which allowed the absolute configuration of natural (+)‐violapyrone C to be assigned by comparison of the optical rotations. This first total synthesis, which proceeded in 22 % yield over 10 steps from (<I>S</I>)‐(–)‐2‐methylbutanol, features silver(I) oxide promoted monobenzylation of 1,4‐butanediol, Wittig olefination, Claisen condensation, Corey–Fuchs reaction, and gold(I)‐catalyzed α‐pyrone synthesis.</P>
Lee, Yeon-Ju,Han, Saem,Lee, Hyi-Seung,Kang, Jong Soon,Yun, Jieun,Sim, Chung J.,Shin, Hee Jae,Lee, Jong Seok American Chemical Society and American Society of 2013 Journal of natural products Vol.76 No.9
<P>Seventeen bromotyrosine-derived metabolites, including eight new compounds, were isolated from a Micronesian sponge of the genus <I>Suberea</I>. Four of the new compounds were psammaplysin derivatives (<B>10</B>–<B>13</B>), and the other four were ceratinamine derivatives (<B>14</B>–<B>17</B>). Of the compounds obtained, the psammaplysins exhibited cytotoxicity against human cancer cell lines (GI<SUB>50</SUB> values down to 0.8 μM), while the ceratinamine and moloka’iamine analogues showed almost no activity. These results suggest that the spirooxepinisoxazoline ring system is a requirement for cytotoxicity and, therefore, may serve as an attractive molecular scaffold for the development of a potent anticancer agent.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jnprdf/2013/jnprdf.2013.76.issue-9/np400448y/production/images/medium/np-2013-00448y_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np400448y'>ACS Electronic Supporting Info</A></P>
Lee, Jung-Ho,Jang, KyoungHwa,Lee, Yeon-Ju,Lee, Hyi-Seung,Sim, Chung J.,Oh, Ki-Bong,Shin, Jongheon American ChemicalSociety and AmericanSociety of Ph 2011 Journal of natural products Vol.74 No.12
<P>Nine new triterpene galactosides and aglycones, along with three known compounds from the rare pouoside class, were isolated from the tropical sponge Lipastrotethya sp. collected from Micronesia. The structures of these new compounds were determined by combined spectroscopic methods and designated as pouosides F-I (4, 8, 10, and 12) and pouogenins A-E (5-7, 9, and 11). The absolute configurations of the asymmetric centers and the cyclohexenone moiety, which had been previously undetermined, were assigned by NOESY analyses and Mosher's methods. Several of these compounds exhibited weak cytotoxicity against the K562 cell line.</P>