Epoxy Moiety Research Articles

Intermediates in the Synthesis of Forskolin. I

In 4-acetyl-3,4-epoxy-3,6,6,8b-tetramethyl-2a,3,4,6,7,8,8a,8b-octahydro- 2H-naphtho[1,8a,8-bc]furan-2-one, C17H22O4, the saturated ring (A) adopts a chair conformation, the cyclohexene ring (B) a distorted half-chair conformation and the furan ring an envelope conformation. The lactone and the epoxy moieties are trans to each other.

Effect of local dynamics on model epoxy resins

AbstractA series of epoxy resins has been prepared with different chain stiffness either in the diepoxide residue or in the diamine crosslinker (1). Furthermore, the crosslink density has been changed by incorporating either monoamine or secondary diamine as a chain extender, but in each system the stoichiometric ratio was maintained (1).Viscoelastic measurements were performed over a wide range of frequencies with the aim of determining the main characteristics associated with the Tg and β relaxation processes (2, 3). In a complementary way, high resolution solid state 13C NMR measurements were carried out to determine the mobilities of the different aliphatic carbons in the epoxy moieties (4).The effects of the chemical structure and of the crosslink density on the mobility of the different groups and the consequences on the Tg values, the amplitude of the β transition and the modulus of the resins are analyzed (5).

Clerodane Diterpenoids from Ajuga decumbens.

A new neo-clerodane diterpene, ajugacumbin G, was isolated from Ajuga decumbens THUNB. (Labiatae), and the structure was characterized as 6α-acetoxy-4α, 17-epoxy-18-(3'-hydroxy-2'-methylenebutyryloxy)-neo-cleroda-13-en-15, 16-olide by 1H-and 13C-NMR spectral study and by comparison with the known compounds of ajugacumbins A and B. Reactions to an epoxy moiety of ajugacumbin compounds with halogen acid, HX (X=Cl, Br and I) and with Jones reagent were prepared to supply some samples with different substituents at C-4 for insect antifeedant examination.

Synthesis of Two Possible Diastereoisomers of the Epoxy Lactone Proposed for Epoxyrollin A

Syntheses of two possible stereoisomeric epoxy lactones (20S,21R)- and (20R,21S)-1 that have been proposed for epoxyrollin A, a structural representative of biosynthetic precursors of tetrahydrofuran annonaceous acetogenins, are described. Protected dihydroxy compound 4, which is the latent epoxy moiety of (20S,21R)– and (20R,21S)-1, was prepared by an 8–step sequence via Sharpless asymmetric dihydroxylation, starting from allyl alcohol 6. Preparation of γ-lactone moiety 5 was conducted by the method reported earlier. A palladium–catalyzed cross coupling reaction of 4 with 5 gave enyne 3, which, by a 3-step sequence, was converted into (20S,21R)- and (20R,21S)-1. The 13C-NMR and mass spectral data of the two synthetic diastereoisomers are not in accordance with those recorded for epoxyrollin A. Consequently, the structure of epoxyrollin A needs to be revised.

The Application of Phosphazene Containing Polymers as Negative Resists in Microlithography

New terpolymers containing phosphazene, epoxy and silicon moieties have been synthesized which were used as negative resists in microlithography. In addition to synthesis and characterization, lithographic properties are discussed.

Photocross-linking of polymers initiated by benzylsulphonium salts as cationic initiators

Photocross-linking behaviour of poly(ethylene-co-glycidyl methacrylate) (EGMA) initiated by benzylsulphonium slats (BSS) has been investigated in relation to negative photoresist. Unlike triarylsulphonium slats which produce Bronsted acids, following the reaction with solvents or monomers, BSS directly produces benzyl cation on photoirradiation at > 300 nm and the resulting benzyl cation attacks the epoxy residues in EGMA to initiate cationic polymerization, leading to interchain cross-linking of the polymer. In this photocross-linking reaction, the efficiency was found to be so high that only 0.15 mol% BSS (based on the epoxy content in the copolymer) was enough to produce an insoluble network of the copolymer. This fact strongly suggests the presence of domains where the epoxy moieties and BSS are concentrated, thereby once initiating species (benzyl cation) are formed photochemically, the cationic polymerization takes place effectively in these domains.

ChemInform Abstract: Reaction of Lithium Trifluoroboratoalkynides with 2,3‐Epoxy‐6‐oxabicyclo(3.3.0)octan‐7‐ol. Synthesis of 13,14‐Didehydro Analogues of Prostaglandin F2α.

AbstractThe reaction between the bicyclo compound (I) and the in situ generated lithium compounds (II) proceeds at the epoxy moiety of (I) to yield a separable mixture of the regioisomers (III) and (IV) with a low selectivity.

Panaxyne epoxide, a new cytotoxic polyyne fromPanax ginseng root against L1210 cells

A new polyacetylene compound with cytotoxic activity against L1210 cells having diyne-ene and epoxy moiety, named panaxyne epoxide, was isolated fromPanax ginseng C.A. Meyer. The chemical structure of the polyacetylene was determined to be tetradeca-13-ene-1,3-diyne-6,7-epoxide by UV, IR,1H-NMR,13C-NMR and mass spectra.

Characterization of GIS Spacers Exposed to SF6 Decomposition Products

SF6 gas-insulated switchgear is a sealed system, but low- level contamination can accumulate and affect spacer performance. The degradation of a number of spacer materials exposed to either direct arcing conditions or arc by-products was investigated to correlate their surface molecular features with changes in electrical performance. Electron Spectroscopy for Chemical Analysis, Scanning Electron Microscopy, Infrared and Thermal Analysis were used to probe the surface of the dielectrics. In the immediate vicinity of the spark, spacer surfaces undergo irreversible chemical, morphological, and physical changes with extensive pyrolysis and surface erosion. There is clear evidence of chemical reactions with high concentrations of fluorine bonded to the organic resin. Exposure of spacer materials to SF6 arcing by-products results in significant reduction in electrical properties with profound changes in the chemical structure of both epoxy moieties and/ or filler particles. This paper will describe the surface characterization techniques as applied to degraded spacer surfaces and discuss the possible degradation mechanisms.

Topical Mosquito Repellents V: Benzyl Ethers

A series of benzylic ethers with hydroxyl, epoxy, and unsaturated moieties was synthesized and evaluated on human skin for repellency against female Aedes aegypti mosquitoes. Compounds exhibiting the longest durations of repellency were those with boiling points of approximately 125°/0.5mm. The case of two monobenzyl ethers of 3,4-dihydroxycyclopentene-1 having the same boiling points but different repellent activity is of interest. None of the compounds examined was as effective as N,N-diethyl-m-toluamide in terms of the duration of topical repellency.