Three new trimeric stilbenes from Gnetum gnemon

Three stilbene trimers (gnemonols D, E, F) were isolated from the root of Gnetum gnemon. The structures were determined by spectroscopic analysis. In addition, the antioxidant activity of the compounds on lipid peroxide inhibition and super oxide scavenging activity were also investigated.     

A new synthesis, including asymmetric synthesis, of alkylidenecyclopropanes by 1,2-CC insertion of cyclobutylmagnesium carbenoides as the key reaction

Treatment of 1-chlorovinyl p-tolyl sulfoxides, derived from ketones and chloromethyl p-tolyl sulfoxide, with lithium enolate of carboxylic acid tert-butyl esters gave adducts in high yields. The adducts were converted to 1-chlorocyclobutyl p-tolyl sulfoxides in four steps in high overall yields. Treatment of the 1-chlorocyclobutyl p-tolyl sulfoxides with cyclopentylmagnesium chloride in THF at −40 °C resulted in the formation of cyclobutylmagnesium carbenoids. The magnesium carbenoid 1,2-CC insertion reaction took place smoothly from the cyclobutylmagnesium carbenoids to afford alkylidenecyclopropanes in good to high yields. An asymmetric synthesis of optically active alkylidenecyclopropane was successfully achieved starting from optically active 1-chlorovinyl p-tolyl sulfoxide.     

Synthesis and Polymerization of 2-(β-Substituted Acryloyl)-1 -Met hacryloyloxy naphthalenes

Some 2-(β-substituted acryloyl)-l-methacryloyloxy-naphthalenes (II) were synthesized by the reaction of the corresponding 2-(β-substituted acryloyl)-l-naphthols with methacryloyl chloride. These monomers were polymerized with 2, 2′-azoisobutyronitrile. The properties of the resulting oligomers as photosensitive resins are described.     

Syntheses and properties of a series of amphiphilic polyacrylamides bearing two long alkyl chains and phosphatidylcholine analogous groups in the side chains

A novel vinyl monomer 2-{(3-acrylamidopropyl)dimethyl ammonio}ethyl 2′-isopropyl phosphate (AAPI) having phosphatidylcholine analogous moiety and a series of new acrylamide monomers containing two long alkyl chains [stearyloleylacrylamide (SOAAm), distearylacrylamide (SSAAm), and n-docosyloleylacrylamide (DOAAm)] were synthesized and characterized. The polyacrylamides ( Va, Vb , and Vc ) were obtained from radical copolymerization of SOAAm, SSAAm, or DOAAm with AAPI in the presence of AIBN as an initiator. The investigations of these copolymers were carried out by x-ray analysis method, DSC, TG-DTA, and viscosity measurement, respectively. The copolymer Vb containing distearyl groups as hydrophobic side chains shows a crystalline state at room temperature, and the ordered structure disappears at high temperature. The phase transition from a crystalline state to a liquid-crystalline state was observed obviously only for copolymer Vb . In addition, the II-A isotherms and A-T isobars of these copolymers were measured and their stable LB films were also prepared. © 1996 John Wiley & Sons, Inc.     

Five Stilbene Glucosides from Gnetum gnemonoides and Gnetum africanum

Five new stilbene glucosides, gnemonosides F, G, H, I, and J were isolated from the stem lianas of Gnetum gnemonoides Brongn and Gnetum africanum Welw along with nine known stilbenoids. The structures of the new compounds were elucidated as gnetin E 4a,4b,4c‐O‐β‐triglucopyranoside ( 2 ), gnetin E 4a,4c‐O‐β‐diglucopyranoside ( 3 ), gnetin C 4a,4b,11a‐O‐β‐triglucopyranoside ( 4 ), gnetin D 4a,4b‐O‐β‐diglucopyranoside ( 5 ), and gnetuhainin A 4a,4b‐O‐β‐diglucopyranoside ( 6 ) on the basis of spectroscopic evidence.     

Vinyl Polymerization. 282. Vinyl Polymerization Initiated by Dimethylhydroxylamine-Titanous(lll) Chloride Redox System

Abstract

The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]^0.5 for DHA concentrations of less than 2.06 × 10^?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] ^0.58 and to [MMA] ^1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made.     

Coupling‐Reagent‐Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids

A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl‐glycyl‐glycine, present in IMREG‐1, also.     

One-pot synthesis of large FePt nanoparticles from metal salts and their thermal stability

One-pot synthesis of FePt nanoparticles larger than 5 nm with controlled composition has been developed by the polyol reduction of platinum acetylacetonate and iron acetylacetonate in excess ligands. The obtained large FePt nanoparticles (6.1 +/- 0.6 nm Fe36Pt64, 5.8 +/- 0.7 nm Fe44Pt56, and 5.1 +/- 0.7 nm Fe49Pt51 nanoparticles) were thermally more stable than the small ones and were hard to coalesce in the in-plane direction for their 2D superlattice.