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1.
N-Acyl derivatives of D,L-acosamine and D,L-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters.  相似文献   

2.
J Leitich 《Tetrahedron letters》1980,21(32):3025-3028
The relative rates of formation of cis and trans [2+2]cycloadducts of benzyne to cis, trans- and cis, cis-1,5-cyclooctadiene, trans- and cis-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.  相似文献   

3.
The 1H and 13C nmr spectra of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d6 or alkaline D2O, clearly show that it exists in a boat-chair-conformation with equatorial carboxyl groups, thus being the first case of boat-chair preference of a bicyclo[3.3.1] nonan-9-one due to the presence of exo,exo-2,4- substituents.  相似文献   

4.
The new compounds 14 and 8 have been isolated from cultures of Aspergillusduricaulis  相似文献   

5.
A new ichthyotoxic toxin was isolated from the unialgal culture of the deleterious Florida red tide organism, Gymnodiniumbreve Davis (Syn. Ptychodiscusbrevis), and its structure was elucidated.  相似文献   

6.
Sterepolide and dihydrosterepolide, new sesquiterpenes isolated from the fungus Stereumpurpureum, are assigned structures 4 and 7, respectively. The assignments are based mainly on spectroscopic studies and similarities to isolactarorufin (5). A possible mode of biogenesis of these isolactarane type sesquiterpenes is discussed.  相似文献   

7.
1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10 (14H,3H,9H,12H)-tetraones (mixed flavins) were prepared by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)-amino-5-deazaflavins with Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral condition in sunlight and a remarkable autorecycling was observed.  相似文献   

8.
A new purine derivative with cytokinin activity was isolated from the cuckoo-pint fruits (Zantedeschiaaethiopica) and identified as 6-(o-hydroxybenzylamino)-2-methylthio-9-β-D-glucofuranosylpurine 1.  相似文献   

9.
Four novel fusicoccane diterpenoids, fusicoplagins A, B, C, and D, have been isolated from the liverwort Plagiochilaacanthophylla subsp. japonica and the structures determined by spectroscopic methods, chemical transformations, and X-ray crystallographic analysis.  相似文献   

10.
Two steroids, 3-oxo-chol-4-ene-24-oic acid (2) andi ts unsaturated analog 4 have been isolated from the dorid nudibranch Aldisasanguineacooperi, and the acid 2 has been shown to have antifeedant properties.  相似文献   

11.
Palladium catalysed alkoxycarbonylation of heterocyclic halides affords a simple and versatile synthesis of both N and S heterocyclic esters where a range of catalysts have been studied and a method to employ inexpensive inorganic bases has been found.  相似文献   

12.
Methods are described for the stereospecific conversion of hydrindenone 3 either to the corresponding trans fused or cis fused hydrindanone (1 or 2, respectively.)  相似文献   

13.
Pinacol E-1-trimethylsilyl-1-propene-3-boronate reacts with aldehydes to form (±)-(R*,S*)-3-trimethylsilyl-4-hydroxy-1-alkenes, which can be deoxysilylated stereoselectively to either 98% Z or 99% E 1,3-dienes, including the separate components of the red bollworm moth pheromone.  相似文献   

14.
The structures 1, 2, and 3 have been proposed for three new diterpenes from Dictyotadichotoma mainly on the basis of spectroscopic evidence.  相似文献   

15.
The EZ equilibrium of the cations of benzo hydroxamic acids, in mineral acid, was studied utilizing 1H NMR spectroscopy, NOEDS and MNDO claculations  相似文献   

16.
Kenji Mori  Hideto Mori 《Tetrahedron》1985,41(23):5487-5493
(1S,5R)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1S,5R)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from (S)-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic (ca. 1.3 % e.e.).  相似文献   

17.
6-Methoxy-2,2-dimethylchromene (I) and five new chromenes (II-VI) were isolated from Lactarius fuliginosus and L.picinus (Basidiomycetes). These unusual structures have been elucidated by spectroscopic methods. 2,2-Dimethylchromene (VII) was identified by GC-MS in L. picinus.  相似文献   

18.
Simarinolide 4a and Guanepolide 5a are new quassinoids with a C25 basic skeleton isolated from a member of the French Guyanan Simaroubaceae, Simaba cf orinocensis H.B.K. The structure 4a was established by spectral means and that of 5a by X-ray diffraction analysis. The previously known simarolide 1 was also isolated.  相似文献   

19.
The isolation of a new metabolite of mixed biogenesis, balearone 1from the brown alga Cystoscirabalearica is described. The structure was determined by an X-ray diffraction analysis.  相似文献   

20.
Two new diterpenelactones named plaunol A (2) and B (3) exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, Crotonsublyratus. Structure of 2 was determined by X-ray analysis of its p-bromobenzoate and structure of 3 was deduced from the results of chemical correlation and the spectral data.  相似文献   

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