A Thermolysis Study of Poly(Trimethylene Phenylphosphinate) and Poly(2,2-Dimethyltrimethylene Phenylphosphinate). NMR and X-Ray Structure of 2-Oxo-2-Phenyl-4,4-Dimethyl-1,2-Oxaphospholan

Abstract

The syntheses of polyphosphinates 2 and 2a by the ring-opening polymerization of cyclic phosphonites 1 and 1a with CH₃I as an initiator have been reported in literature^1–3. These polymers thermally decompose to give oxaphospholan 3 and 3a. In this paper, we present evidence on the mechanism of their formation.     

Synthesis of partially benzylated arabinofuranosides,NMR analysis,and application to oligosaccharide synthesis

The preparation and NMR analysis of 2,3-di-O-benzyl arabinofuranosides have been described. In DMSO-d₆, the sugar adopts a conformation in which the hydroxyl groups are in an equatorial position; the equilibrium composition is determined by steric factors. In CDCl₃, the sugar adopts a conformation in which the intramolecular hydrogen bonding plays an important role in determining the equilibrium composition. The use of 2,3-di-O-benzyl arabinose in the synthesis of oligoarabinofuranosides enabled the synthesis of α- or β-linked furanosides.     

Facile Syntheses of (6S)-6-Fluoroshikimic Acid and (6R)-6-Hydroxyshikimic Acid

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｈｉｋｉｍａｔｅｐａｔｈｗａｙｉｓａｎｉｍｐｏｒｔａｎｔｂｉｏｓｙｎ ｔｈｅｔｉｃｓｅｑｕｅｎｃｅｉｎ ｐｌａｎｔｓ ,ｆｕｎｇｉａｎｄｍｉｃｒｏｏｒｇａｎｉｓｍｓｆｏｒｔｈｅｃｏｎｖｅｒｓｉｏｎｏｆｃａｒｂｏｈｙｄｒａｔｅｓｔｏｔｈｅａｒｏｍａｔｉｃａｍｉｎｏａｃｉｄｓ (Ｌ ｐｈｅｎｙｌａｌａｎｉｎｅ ,Ｌ ｔｙｒｏｓｉｎｅａｎｄＬ ｔｒｙｐｔｏｐｈａｎ)ａｎｄｐｒｅｃｕｒｓｏｒｓｔｏｔｈｅｆｏｌａｔｅｃｏｅｎｚｙｍｅｓ ,ａｌｋａｌｏｉｄｓａｎｄｖｉｔａｍｉｎｓ[1] .Ａｓ…     

A proton and carbon-13 nuclear magnetic resonance study of neopentylmercury compounds

Substituent effects on ¹⁹⁹Hg¹H and ¹⁹⁹Hg¹³C spinspin coupling constants have been studied for neopentylmercury derivatives, (CH₃)₃CCH₂HgR(or X), where R is covalently bonded Me, Et, t-Bu, neopentyl, and vinyl, and X is easily ionizable CN, Br, Cl, OCOCH₃, and ONO₂. Linear relationships exist between the methylene J(¹³CH) and ²J(HgH), ⁴J(HgC) and ²J(HgC) and ³J(HgC); but deviations from linearity occur for the chloride, bromide, acetate, and nitrate in the relationships between ²J(HgH) and ⁴J(HgH), ²J(HGH) and ²J(HGC). These deviations are discussed in terms of hyperconjugative p_πd_π bonding between the methylene CH bonds and mercury.     

Fortion and Reactions of Phosphonium Inner Salt, ≡ P+ C6H4O −p

Abstract

Thermolysis and reactions of methyltris(p-methoxyphenyl)phosphonium iodide with triphenylphosphine are reported. NMR and mass spectr evidence for the formation of phosphonium inner salts, →P₆,H₆ O^?-p, is presented.     

Laser machining of silicon nitride based composite cantilever structures

Cantilever structures from silicon nitride based composite ceramic materials were produced using laser cutting. A picosecond laser was used to cut two-dimensional meso sized cantilever structures up to 450 μm thickness in conductive and insulating ceramics. A practical experimental based approach was used, where various parameters of the laser cutting process were altered to produce a cut surface with a damage zone of 5–10 μm. The quality of the cut ceramics was investigated by optical and scanning electron microscopy. The results are presented along with the properties of the laser cut surface, including the damage zone, formation of cracks and the reaction products.     

Syntheses of ethyl 3-deoxy-3,3-difluoro-d-arabino-heptulosonate and analogues

The difluorinated analogues of 3-deoxy-d-arabino-heptulosonic acid (DAH) 12, 24 and its enantiomer have been synthesised from d- and l-erythrose via a Reformatsky reaction which gave a mixture of diastereoiosmers in favour of the anti isomer.     

A unique approach to the synthesis of a dengue vaccine and the novel tetrasaccharide that results

An approach to the development of a dengue vaccine by synthesizing the hexasaccharide epitope on the viral surface is examined. The stereochemical and structural challenges include the synthesis of a β-mannoside bond. Synthesis of this bond is approached via a trisaccharide analogue portion of the epitope. A novel tetrasaccharide with a mannose–mannose anomeric linkage results in the course of the synthetic attempts.