Chain-extended Compounds

2 Chain-extended Compounds. - Higher sugars have been produced by osm ation of icnown heptenoses and oct-dienoses The ihamnulose 1-phosphate aldolase-catalysed condensation of 

Reagents i. AD-mix-p, Bu OH, H2O ii, pH 1 iii. DHAP, ihanmulosel-pbosphate aldolase iv, phosphate 

One carbon elongation has also been achieved by displacement of primary triflate groups vrith potassium cyanide/ and by opening of S,6-epoxide 40 wth 2-lithio-2-trimethy]silyl-l,3-dithiane to 2- 

Reagents i, Glycerol phosphate oxidase ii, galactose oxidase iii, L-rhamnulose phosphate aldolase iv, phosphatase 

C-6-Allylated pyranoses and C-S-allylated fliranoses were prepared from the corresponding iodides by Keck radical coupling with allyltributyltin (e.g. 44- 4S). The selective formation of product 47 in the chain-extension of the acetal-protected uronic acid derivative 46 by radical addition of methyl acrylate using Barton s method was ascribed to addition from the less hindered side to a conformationally stable radical intermediate the peracetate 48 furnished a 1 1 mixture of 49 and 50.  

The diastereomeric C,2 (Z)-allylic alcohols 30 [ R/S) 1 2] have been obtained by addition of lithiated alkyne 28 to dialdose derivative 29, followed by partial hydrogenation of the triple bond, and the two ( )-isomers 32 7 3] were formed when the lithiated alkene derived from 

Chain-extension at C-6 of hexodialdose derivative 33 was involved in the synthesis of the linear C-8-C-8-linked dipyranyl dimer 34, and the diastereomeric alcohols 35, obtained by Grignard reaction on the corresponding C-6-aldehyde, were used as glycosyl donors in the preparation of C-6-methylated analogues of disaccharide 36 and of a related trisaccharide 

2 Chain-extension at the Reducing End.- Reaction of the four unprotected D-aldopentoses with the stabilized ylid PhjPsCHCOjMe, in the presence of copper(II) acetate to suppress cyclization to fiiranose derivatives, gave ( )-alkenes 39 (isolated as the tetraacetates or diacetonides) in 

7-Dideoxyheptulosonic ester 46 has been synthesized fiom glycal 43 by way of lactone 44 and dithiane 45, and KDN has been obtained by condensation of D-mannose with oxalacetic acid under basic conditions. Siereocontrolled synthesis of polyol chains employing 2-acetylthiazole as 

Reagents i, 2 Acetylthiazole, Bu OLi ii, Me4NBH iii. DIBAL iv, Me2(COMe)2, camphorsulfonic acid 

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S-Dihydtoisoxazole derivatives, e.g. 110, could be obtained from iodo-tosylates such as 109 as shown in Scheme 22. They have potential for production of chain extended compounds, e.g. 111. as the nitro-group can be displaced by carbanionic reagents. Addition of diazomethane to 3 -deoxy-3 -methylene-nucleosides yields 3 -spi>o-pyrazoline derivatives whidi can be converted to 3 -spiro-cyclopropane analogues with loss of nitrogen. ... 

A number of syntheses of acyclic chain extended compounds have been reported this year. 2-Deoxy-D-glucose has been elaborated to 213 a precursor to the C14-C24 section of tautomycin, and a synthesis of the C1-C12 fragment 216 of amphotericin B utilizes a Wittig coupling of two carbohydrate components, the 3-deoxy-D-ribofuranose derivative 215 and the galactose-derived 214.91... 

Chain-extended Compounds.- A review with 200 references on recent advances in the synthesis of C, -Q sugars, including neuraminic acid analogues, has been published. ... 

Chain-extended compounds of both the d- (81) and the L-series (83, 85) bearing an additional chiral centre were also isomerised (Scheme 27), albeit requiring longer reaction times, leading to interesting higher carbon ketoses (82,84, and 86, respectively). 

Chain-extended Compounds. - De Las Heras et al have presented a summary of their contributions to the synthesis of branched-chain and higher sugars and nucleosides. ... 

Chain-extended Compounds. - Unusual hexoses and higher carbon sugars have been produced by use of fructose 1,6-diphosphate aldolase which catalysed firstly, in combination with triosephosphate isomerase, the release of dihydroxyacetone phosphate (DHAP) from fructose 1,6-diphosphate and secondly the stereospecific condensation of DHAP with a variety of simple aldehydes. Two examples are given in Scheme 7. ... 

Derivatives of CPD have also been incorporated into these resins. CPD and 2-butene-l,4-diol have been condensed in ethanol and catalyticaHy hydrogenated in situ to give 2,3-bis(hydroxymethyl)bicyclo[2.2.1]heptane (51). This latter compound is used as a chain extender in polyesters for engineering plastics (52). 

BMI also reacts with dienes to form Diels-Alder adducts [12]. When BMI reacts with a a,(n-biscyclopentadienyl compound or other bis-diene resin, the bis-maleimide chain is extended by the Diels-Alder reaction. Bis-maleimide, chain extended with bis-diene, is not used in adhesives. However, as the Diels-Alder reaction is reversible, there may be a possibility of recyclability of the cured resin by depolymerization of the backbone (Fig. 6). 

A chain extender could be selected from the following compounds ethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, neopentanediol, hexanediol, methyl-dihydroxylethyl amine (MDEA) [9], etc. These should be as dry as possible. 

AlSCl has an orthorhombic structure, with the lattice constants a - 8.09, b = 10.52, c = 3.86 A, andZ = 4. It is probably isotypic with SbSCl and BiSCl, crystallizing in a layer type of lattice (157) (see Section XII,C,5). The selenide halides are monoclinic, with the probable space-group P2,/m. The lattice constants are given in Table XVII. The constancy of the b parameters for all three compounds suggests the general presence of an Al-Se chain extending in that direction (266). 

Extended linear chain inorganic compounds have special chemical and physical properties [60,61], This has led to new developments in fields such as supramolecular chemistry, acid-base chemistry, luminescent materials, and various optoelectronic applications. Among recent examples are the developments of a vapochromic light emitting diode from linear chain Pt(II)/Pd(II) complexes [62], a luminescent switch consisting of an Au(I) dithiocarbamate complex that possesses a luminescent linear... 

There is a wide range of chain extenders commercially available for PET (Table 14.2). Bifunctional chain extenders promote linear chain extension while tri- and tetra-functional chain extenders promote chain branching. Such reactive compounds are also known as repair additives since they can reverse the molecular weight loss of hydrolytically damaged PET. 

Aromatic carboxylic dianhydride chain extenders (e.g. PMDA) are a low-cost way of converting recycled PET flakes into high-IV crystalline pellets that can be used in high-value applications (e.g. bottles, strapping, foam, engineering alloys/compounds, etc.) (see Figure 14.2). PMDA is an effective chain extension additive for thermoplastic polyesters such as PET and PBT. It is suitable for the following applications ... 

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