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101.
This paper describes the stereoselective outcome of the intramolecular Diels-Alder furan (IMDAF) reaction of substituted (2S,3S)-ethanolamides 9-13, which were synthesised from a furyl substituted cyanohydrin. The latter was obtained from 2-furaldehyde with high enantioselectivity by an oxynitrilase catalysed addition of hydrogen cyanide. The stereochemistry of the IMDAF products was shown to be dependent on the size of the ethanolamide substituents R. Small substituents (H, Me, CN) gave exclusively exo-cycloaddition, whereas more bulky ones (Ph, Et) gave both evo- and endo-addition, the larger phenyl substituent giving a high endo-exo-ratio.  相似文献   
102.
Summary Epoxidation of the acridone alkaloid acronycine (1) resulted in hydroxylation at the aromatic ring giving 5-hydroxyacronycine (3). The same reaction on 1,3-dimethoxy-10-methyl-9(10H)-acridinone (5) gave 1,3-dimethoxy-2-hydroxy-10-methyl-9(10H)-acridinone (6), 1,3-dimethoxy-2-hydroxy-4-peroxy-10-methyl-9(10H)-acridinone (8), and 1,3-dimethoxy-2,4-diperoxy-10-methyl-9(10H)-acridinone (9).
Naturstoffchemie, 137. Mitt.: Oxidierung von Acridonalkaloiden: Synthese des 5-Methoxyacronycins (Kurze Mitt.)
Zusammenfassung Die Epoxidierung des Acridonalkaloids Acronycin führte zu einer Hydroxylierung des aromatischen Rings, wobei 5-Hydroxyacronycin (3) entstand. Die gleiche Reaktion mit 1,3-Dimethoxy-10-methyl-9(10H)acridinon (5) ergab 1,3-Dimethoxy-2-hydroxy-10-methyl-9(10H)acridinon (6), 1,3-Dimethoxy-2-hydroxy-4-peroxy-10-methyl-9(10H)acridinon (8) und 1,3-Dimethoxy-2,4-diperoxy-10-methyl-9(10H)acridinon (9).
  相似文献   
103.
Penicillamine Complexes of Nickel, Chromium, and Molybdenum — Structural Particularity and Biological/Medical Relevance The compounds Tl2[NiII(H2O)6][NiII(D-pen)(L-pen)]2[NiII(SCN)2(H2O)4] 1 , Tl[NiII(D-pen)2H] · H2O 2 , Tl[CrIII(D-pen)2] 3 , and Na2[MoO4(pen)2] · 3 CH3OH · 3 H2O 4 have been prepared by the reaction of nickel nitrate (for 1 ), nickel acetate (for 2 ), potassium chromate (for 3 ), and sodium molybdate (for 4 ) with D- and D, L-penicillamine, respectively. They were characterized by single-crystal X-ray structure analysis and other physical methods. Whereas penicillamine acts as a bidentate (N, S)-ligand in 1 and 2 , CrIII (in 3 ), and MoV (in 4 ) are coordinated to the three ligand atoms N, O, and S. The presence of three different types of NiII-complexes a cationic, a neutral, and an anionic one in 1 is remarkable. For crystal data see Inhaltsübersicht.  相似文献   
104.
The K-Selectride reduction at low temperature (-45°C) of 7-oxo-5α-holestan-3β-yl acetate and methyl 7-oxo-3α-hydroxy-5(β-cholanoate resulted in almost quantitative yield of the 7α-alcohol in the 5α-compound but only moderate yield of the 5β-analog. The simultaneous reduction of two carbonyl groups in the 3 and 7 positions afforded good to excellent yields of the diaxial diol in planar steroids (methyl 3,7-dioxo-5α-cholanoate, 3,7-dioxo-5α-cholestane and methyl 3,7-dioxo-5α-cholestan-27-oate) and only 14% of 3α,7α-(OH)2 from methyl 3,7-dioxo-5β-cholanoate.  相似文献   
105.
The synthesis of a novel unnatural carbocyclic analog of the acetylcholine esterase inhibitor galanthamine with a K3[Fe(CN)6] promoted oxidative tandem cyclization as the key step is reported.  相似文献   
106.
107.
A synthesis of new boron containingMannich bases of salicylamide by reaction of salicylamide, formaldehyde and boron-heterocycles is reported.
VIII. Mitteilung:Stump, R. K., Zimmerman jr., H. K., Schleppnik, A. A., Gutsche, C. D., Liebigs Ann. Chem.667, 18 (1963).  相似文献   
108.
We present investigations on noncovalent bonding and supramolecular self-assembly of two related molecular building blocks at a noble metal surface: 4-[trans-2-(pyrid-4-yl-vinyl)]benzoic acid (PVBA) and 4-[(pyrid-4-yl-ethynyl)]benzoic acid (PEBA). These rigid, rodlike molecules comprising the same complementary moieties for hydrogen bond formation are comparable in shape and size. For PVBA, the ethenylene moiety accounts for two-dimensional (2-D) chirality upon confinement to a surface; PEBA is linear and thus 2-D achiral. Molecular films were deposited on a Ag(111) surface by organic molecular beam epitaxy and characterized by scanning tunneling microscopy. At low temperatures (around 150 K), both species form irregular networks of flat lying molecules linked via their endgroups in a diffusion-limited aggregation process. In the absence of kinetic limitations (adsorption or annealing at room temperature), hydrogen-bonded supramolecular assemblies form which are markedly different. With PVBA, enantiomorphic twin chains in two mirror-symmetric species running along a high-symmetry direction of the substrate lattice form by diastereoselective self-assembly of one enantiomer. The chirality signature is strictly correlated between neighboring twin chains. Enantiopure one-dimensional (1-D) supramolecular nanogratings with tunable periodicity evolve at intermediate coverages, reflecting chiral resolution in micrometer domains. In contrast, PEBA assembles in 2-D hydrogen-bonded islands, which are enantiomorphic because of the orientation of the supramolecular arrangements along low-symmetry directions of the substrate. Thus, for PVBA, chiral molecules form 1-D enantiomorphic supramolecular structures because of mesoscopic resolution of a 2-D chiral species, whereas with PEBA, the packing of an achiral species causes 2-D enantiomorphic arrangements. Model simulations of supramolecular ordering provide a deeper understanding of the stability of these systems.  相似文献   
109.
Chlorocarbenium salts - of the Vilsmeier-Arnold type react with the silylated isocyanuric acid to give 1-oxa-3-azabutatrienium salts under mild conditions. From reactions of diarylchloromethenium salts - with and ketones or tertiary carboxamides high yields of 2-azaallenium salts were obtained. A few chloro substituted 2-azaallenium salts were prepared from and carbonyl compounds. The mechanisms of the new reactions are discussed.  相似文献   
110.
Polyurethane (PU) cationomers have been synthesized by quaternizing tertiary amine-containing linear polyurethanes using different quaternizers containing acid groups. The effect of chemical structure of PU cationomers on the physical properties was studied. The mechanical properties of PU cationomers were improved with decreasing molecular weight of poly(caprolactone) glycol, and increasing concentration of quaternary ammonium. Decreasing the carbon number in the alkyl group of the N-alkyl diethanol-amine chain-extenders, and using rigid symmetrical diisocyanates, the mechanical properties of the PU cationomers were increased. The effects of these factors on the glass transition temperature of PU cationomers were also examined. The mechanical properties of the PU cationomers decreased by immersion in water and recovered after removal of the water.  相似文献   
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