Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

Studies on the Catalytic Properties of Magnesia Supported on γ-Alumina

ＩｎｔｒｏｄｕｃｔｉｏｎＧｌｙｃｏｌｅｔｈｅｒｓａｒｅｉｍｐｏｒｔａｎｔｉｎｄｕｓｔｒｉａｌｄｅｒｉｖａｔｉｖｅｓｏｆｅｐｏｘｉｄｅｓ .Ｐｏｌｙｅｔｈｙｌｅｎｅ ｇｌｙｃｏｌｅｔｈｙｌｅｔｈｅｒｓａｎｄｐｏｌｙｐｒｏｐｙｌｅｎｅｇｌｙｃｏｌｅｔｈｙｌｅｔｈｅｒｓａｒｅｔｗｏｉｍｐｏｒｔａｎｔｓｅｒｉｅｓｏｆｐｒｏｄｕｃｔｓ .Ｇｌｙｃｏｌｅｔｈｅｒｓａｒｅｇｏｏｄｓｏｌｖｅｎｔｓｄｕｅｔｏｔｈｅｐｒｅｓｅｎｃｅｏｆ—Ｏ—ａｎｄ—ＯＨ ｇｒｏｕｐｓ.Ａｓａｒｅ ｓｕｌｔ ,ｔｈｅｙａｒｅｗｉｄｅｌｙｕｓｅ…     

Selective Deoxygenation of Nitrones Mediated by Sm/CoCl_26H_2O Reductive System

Aldimines are an important class compounds1 which can be prepared by selective deoxygenation of nitrones. Thus more attention was paid to the selective deoxygenation of nitrones in organic synthesis. The reducing reagents, include low-valent titanium2, acetic formic anhydride3, sodium hydrogen telluride4, tributyltin hydride4, terathiomolybdate5, metallic indium in aqueous media6, zinc-aluminum trichloride7, aluminum iodide8, triphenylphosphine9, etc. However, there are various limitations …     

Mild Hydrothermal Synthesis and Optical Properties of the Complex Fluoride KMgF_3 Doped with Eu

Perovskite complex fluorides have attracted great interests due to their particular physical properties such as antiferromagnetic characteristics1, photoluminescence behavior2. Complex fluorides are usually prepared by solid state reactions at high-temperature. In spite of inert atmosphere, it is inevitable to contain a bit of oxygen. This has great effect on the luminescent character of rare earth ions. There are also reports about synthesizing some binary fluorides by high-temperature hy…     

Two New Dammarane Glycosides from the Acid Hydrolysis Product of Panax Notoginseng

In our continuing research works on Panax notoginseng (Burk.) F. H. Chen, a famous traditional Chinese herb medicine1, two new dammarane glycosides named notoginsenosides T1 (1) and T2 (2) were isolated from the mild acid hydrolysis products of the root saponins. We report herein the structure elucidation of these two novel glycosides.Notoginsenosides T1(1) was obtained as white solid, [(] = +14.49 (0.50, MeOH). Its negative mode HR-FAB-MS spectrum showing the quasimolecular ion peak a…     

NaIO_4-Catalyzed Bromination of the Aromatic Ring of Lappaconitine

Lappaconitine 1, a bisnorditerpenoid alkaloid, was isolated from many plants of Aconitum species such as A. barbatum var. pulerulum and A. sinomontanum (Ranunculaceae)1-3, and used clinically for treatment of analgic disease as a nonaddicted drug in China4, and as an antiarrythmic in Uzbekistan5. In order to search for high activity, low toxicity compounds, we have carried out the structure modifications of lappaconitine. In this case, an attempt to induce the oxygenated group at C-10 in 1 b…     

A New Norditerpene from Miliusa balansae Finet et Gagnep

The plant Miliusa balansae Finet et Gagnep. is used in Chinese folk medicine for different symptom such as gastropathy and glomerulonephropathy. There is no report about its chemical investigation. In this study a new norditerpene with novel skeleton, named miliusate (1) was isolated, and its structure was established by spectral evidence.Compound 1 was obtained as white flaky crystal, mp 89-91(C; Its molecular formula C20H26O5 was provided by quasi-molecular ion [M+H]+ at m/z 347.17970 (c…     

An Improved Synthesis of trans-3,3b,4,9b,10,11-Hexahydro -6-methoxy-9b-methyl-7- (1-methylethyl) phenanthro {1,2-c[furan-1,5-dione]}

The diterpenoid triexpoxides lactone triptolide is a potent antileukemic, antiflammatory, immunosuppressive and antifertile principle of Tripterygium wilfordii Hook f.1,2. Many methods of synthesis of this compound have been reported in which trans-3,3b,4,9b,10, 11-hexahydro-6-methoxy-9b-methyl-7- (1-methylethyl) phenanthro {1,2-c [furan-1,5- dione]} 4 was an important intermediate. In one reported synthesis, compound 4 was obtained by CrO3/AcOH oxidation of triptophenolide methyl ether 1, b…     

Theoretical Study of the Sensitivity-Improvement Effect of Phosphoryl Group in Mass Spectrometry of Small Peptides

Mass spectrometry plays an important role in peptide sequencing since the invention of soft ionization techniques, such as fast atom bombardment (FAB), electrospray (ESI) and matrix-assisted laser desorption/ionization (MALDI). In our previous work, it was found that phosphorylation on the N-terminal of small peptides could enormously improve their sensitivity in FAB-MS1.To understand the sensitivity-improvement effect of phosphoryl group, the energies for the protonation of glycylglycin…     

Quantized Nanocrystalline CdTe Thin Films

Size quantized nanocrystalline semiconductor thin films have attracted considerable interest in the photoelectrochemical studies1,2. In this paper, we report a pronounced size quantization in nanocrystalline CdTe thin films which is less extensively studied.Nanocrystalline CdTe thin films were electrodeposited on conducting glass by asymmetric rectangular pulse in dimethylsulfoxide solution containing 6 mmol/L Te, 0.75 mmol/L Cd(ClO4)2, 18 mmol/L triphenylphosphine and 0.1 mol/L LiClO4 a…