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1.
Prasat Kittakoop Sombat Nopichai Nuntawan Thongon Panarat Charoenchai Yodhathai Thebtaranonth 《Helvetica chimica acta》2004,87(1):175-179
Two new antimycobacterial dibenzo[b,f]oxepins, bauhinoxepins A (=3,3,5‐trimethylbenzo[b]pyrano[g][1]benzoxepin‐6,11‐diol; 1 ) and B (=6‐methoxy‐7‐methyl‐2‐(3‐methylbut‐2‐enyl)dibenzo[b,f]oxepine‐1,8‐diol; 2 ), were isolated from the roots of Bauhinia saccocalyx, and their structures were elucidated by analysis of spectroscopic data. Bauhinoxepins A and B exhibited antimycobacterial activities with respective minimum‐inhibitory concentrations (MIC) of 6.25 and 12.5 μg/ml. They were inactive (at 20 μg/ml) against the malarial parasite, and also inactive (at 20 μg/ml) towards the Vero, KB, and BC cell lines. 相似文献
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Vinylogous Dieckmann condensations equivalent to enolexo-exo-trig and enolendo-exo-trig cyclisations have been investigated. Five membered rings were smoothly obtained from the former whereas the latter cyclisations occurred with six but not with five membered ring systems. 相似文献
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A ChaiyanurakkulR Jitchati M KaewpetS Rajviroongit Y Thebtaranonth P ThongyooW Watcharin 《Tetrahedron》2003,59(49):9825-9837
Deprotonation of an oxiranyl β-proton takes place in a stereoselective manner providing the corresponding oxiranyl ‘remote’ anion. The anion is stabilized by chelation between the lithium and the carbonyl moiety of an ester, lactone, imide, or keto-group in the form of a five-membered cyclic intermediate. Certain ester-stabilized oxiranyl anions are stable and can be left in THF solution at −78°C for several hours. The generated anions undergo a stereoselective alkylation reaction to provide products, which could be useful intermediates in the synthesis of bioactive naturally occurring α-methylene bis-γ-butyrolactones. 相似文献
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Isomeric exocyclic and endocyclic dienolates 5 and 6 were generated and while 6 reacted with electrophiles exclusively at the α -position the regiospecificity of 5 was found to be dependent on the type of electrophile employed. 相似文献
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Nucleophiles add in a Michael fashion to α-methylene cyclopentenones regiospecifically at the exocyclic cisoid-enone double bond. 相似文献
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J Lertvorachon Y Thebtaranonth T Thongpanchang P Thongyoo 《The Journal of organic chemistry》2001,66(13):4692-4694
Stereospecific deprotonation of the epoxy proton at the beta-position of the alpha,beta-epoxy esters 5 and 6 yielded oxiranyl "remote" anions 7 and 8, which could then be used for alkylation. The anions 7 and 8 underwent a consecutive aldol lactonization to give, respectively, epoxy lactones 11 and 13 with high stereoselectivity. Generation of the remote anions as well as their stereoselective reactions served as a new synthetic route to the naturally occurring alpha-methylenebis-gamma-butyrolactones, 1. 相似文献
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[reaction: see text] An unusually bridged epidithiodiketopiperazine, pretrichodermamide A (3), was isolated from the fungus Trichoderma sp. BCC 5926. During the extensive effort to crystallize 3 for X-ray crystallographic analysis, conversion of this compound to trichodermamide A with coproduction of S(8) occurred. 相似文献
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Chongdee NilanontaMasahiko Isaka Rachada ChanphenNuntawan Thong-orn Morakot TanticharoenYodhathai Thebtaranonth 《Tetrahedron》2003,59(7):1015-1020
Two new enniatins H (3) and I (4), whose substituents on 2-hydroxycarboxylic acid moieties were different from those of known compounds, were isolated, together with known enniatins B (1) and B4 (2), from the insect pathogenic fungus Verticillium hemipterigenum BCC 1449. Structures of these compounds were elucidated by spectroscopic means. Studies on precursor-directed biosynthesis with strain BCC 1449 led to the production and identification of three analogs, enniatins G (5), C (6) and MK1688 (7), as well as the stereochemical elucidation of 3 and 4. Enniatins 1-7 were evaluated for their antiplasmodial and antimycobacterial activities. 相似文献
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