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11.
Reaction of N-tert-butyloxycarbonylasparagine (Boc-Asn) with 2 equiv of benzyl bromide in presence of cesium carbonate led to N-benzyl-3-Boc-amino-pyrrolidin-2,5-dione 1a (N-benzyl-3-Boc-aminosuccinimide). Borane dimethylsulfide reduced 3-Boc-aminopyrrolidine-2,5-dione 1a into 3-Boc-aminopyrrolidin-2-one 2a. The same procedure could also be used to prepare derivatives 1 and 2 substituted on the aromatic ring. 相似文献
12.
SYNTHESIS OF MESOPOROUS POLY(STYRENE-co-MALEIC ANHYDRIDE)/SILICA HYBRID MATERIALS VIA A NONSURFACTANT-TEMPLATED SOL-GEL PROCESS* 总被引:1,自引:0,他引:1
Jie-bin Pang Kun-yuan Qiu Yen Wei Department of Polymer Science Engineering College of Chemistry Molecular Engineering Peking University Beijing China. Department of Chemistry Drexel University Philadelphia Pennsylvania USA. 《高分子科学》2000,(5):469-472
Mesoporous poly (styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis wasachieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymerin the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template orpore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m~2/g) andpore volumes (e.g. 0.6 cm~3/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, porevolumes and pore diameters of the hybrid materials increase. 相似文献
13.
An enantiospecific synthesis of Schinzer's ketone 3 from (R)-(+)-pulegone via alpha-carbonyl radical cyclization was accomplished. This work also constitutes an enantiospecific formal syntheses of (-)-pinguisenol and (-)-alpha-pinguisene. The intermediate ketone 4 would be useful for the synthesis of other pinguisane-type sesquiterpenes. 相似文献
14.
A concise, stereodefined synthesis of compactin lactone is described. Samarium(II) iodide mediated intramolecular Reformatsky reaction is the key step in the synthesis. 相似文献
15.
Kaale E Govaerts C Hoogmartens J Schepdael AV 《Rapid communications in mass spectrometry : RCM》2005,19(20):2918-2922
Aminoglycoside antibiotics are widely used to treat serious Gram-negative and Gram-positive bacterial infections. The lack of a UV chromophore presents a problem in the analysis of aminoglycosides. Derivatization with 1,2-phthalic dicarboxaldehyde (OPA) in the presence of a thiol made it possible to introduce a UV chromophoric thioisoindole moiety. A qualitative mass spectrometry study was carried out to confirm the molecular identity of the products formed. The conditions described earlier to derivatize gentamicin and kanamycin yielded products in which all primary amino groups are fully derivatized. On the other hand, with tobramycin and amikacin, there was also formation of incompletely derivatized products that contained one thioisoindole group less than the fully derivatized product. This study has therefore brought an additional insight into the nature of the OPA-aminoglycoside derivatives studied. 相似文献
16.
Colloidal palladium nanocatalysts prepared by in situ reductions of palladium chloride were immobilized and protected by either of two water-soluble polymers. The particle sizes and size distributions of the palladium colloids were determined by transmission electron microscopy. Their selectivities as catalysts were determined by comparing the extents of hydrogenation of carefully chosen pairs of small-molecule olefins. There was found to be high hydrogenation selectivity with regard to cyclic vs. noncyclic olefins. Selectivity was relatively low, however, among olefins that differed only in size (such as hexene vs. octene), or olefins differing only with regard to the positions of the double bonds (such as 1-octene vs. 3-octene). Selectivity could be improved by careful choice of the immobilizing polymer, and by its use at relatively high concentrations. 相似文献
17.
Cycloaddition of 1,3-diphenyl-2-azaallyllithium to tolane, diphenylbutadiyne and 1,4-diphenylbutenyne E produces quantitatively 2,3,4,5-tetraphenylpyrrole, 3-phenylethynyl-2,4,5-triphenyl-3-pyrroline and 3-phenylethynyl-2,4,5-triphenylpyrrolidine, respectively. Treatment before hydrolysis with benzyl bromide or dimethl sulfide gives N-alkyl-substituted derivatives. The structure of 3-pyrrolines was established by spectral data and chemical correlations. Stereochemical courses of this new synthetic method for 3-pyrrolines are discussed. 相似文献
18.
Journal of Global Optimization - Improperly efficient solutions in the sense of Geoffrion in linear fractional vector optimization problems with unbounded constraint sets are studied systematically... 相似文献
19.
Total synthesis of polycavernoside A, a lethal toxin of the red alga Polycavernosa tsudai 总被引:1,自引:0,他引:1
Blakemore PR Browder CC Hong J Lincoln CM Nagornyy PA Robarge LA Wardrop DJ White JD 《The Journal of organic chemistry》2005,70(14):5449-5460
[structure: see text] Two approaches to the synthesis of the aglycon 120 of polycavernoside A (1) were developed, only one of which was completed. The successful "second-generation" route assembled the aglycon seco acids 102 and 106 via Nozaki-Hiyama-Kishi coupling of aldehyde 70, prepared from methyl (S)-3-hydroxy-2-methylpropionate (72) and (S)-pantolactone (73), with vinyl bromide 71. The latter was obtained from a sequence which commenced from the silyl ether 24 of 3-hydroxypropionaldehyde and entailed cyclization of (Z)-zeta-hydroxy-alpha,beta-unsaturated ester 82. Regioselective Yamaguchi lactonization of trihydroxycarboxylic acids 102 and 106 and subsequent functional-group adjustments led to macrolactone 120, to which the fucopyranosylxylopyranoside moiety was attached. Stille coupling of the glycosidated aglycon 128 with dienylstannane 129 furnished polycavernoside A in a synthesis for which the longest linear sequence was 25 steps. The overall yield to lactone 120 was 4.7%. 相似文献
20.
The light-initiated halogenation of bicyclo[3.2.1]octene-2, its 3-phenyl and 3-bromo derivatives with N-bromosuccinimide and t-butyl hypochlorite resulted in the exclusive formation of the exo-4-halobicyclo[3.2.1]octene-2-derivatives. 相似文献