Brigitte I. Glänzer

N.M.R. Spectroscopy of Fluorinated Monosaccharides

Publisher Summary This chapter discusses the application of nuclear magnetic resonance (NMR) spectroscopy for the analysis of fluorinated monosaccharides. Within the past two decades, the importance of NMR spectroscopy has enlarged tremendously. Its advantages over other methods in the structural and conformational analysis of complex molecules such as natural products, and particularly with regard to the still-increasing importance of medical investigations using NMR techniques, is abundantly evident. Because destruction of the sample is avoided, different NMR experiments can be performed repeatedly and the analysis of the spectra is usually convenient, simple, and fast. This methodology is exceptionally free from artifacts, thus, allowing the detailed analysis of conformational behavior in solution in comparison with the conformation in the solid state. Double- and triple-resonance techniques and isotopic labeling of compounds, together with the use of Fourier-transform spectroscopy at very high field-strength now allows the acquisition of high-resolution, NMR spectra. Because of these great improvements, all magnetic nuclei can now be used in the NMR analysis of fluorinated monosaccharides including 1H, 13C, 15N, and 19F.

Graphite-Metal Compounds

Publisher Summary This chapter discusses the most recent and important developments in the field of graphite and the structural properties and use of these compounds in organic and organometallic chemistry. Graphite has a lamellar structure, with an interlayer distance of 0.335 nm. Besides the large number of reagents that can be intercalated, a number of different types of graphites are used. The most commonly used potassium–graphite intercalation compound, C 8 K, shows an interlayer distance of 5.34 A, and all carbon layers are separated by a layer of K. Differences among the alkali metals in behavior toward graphite have been explained in terms of electron transfer. Pure yellow, first-stage compounds of Ba and Sr with graphite were prepared by the direct action of metal vapor on graphite in metallic tubes sealed under vacuum. C 8 K in toluene, benzene, or isopropylbenzene can act as an alkylation catalyst in the presence of ethylene to yield the corresponding nuclear and side chain-alkylated aromatic hydrocarbons. Graphite intercalation compounds can act as mild anionic polymerization initiators offering some benefits in comparison to analogous reactions in homogeneous medium or to metal dispersions.

Reaction of acetyl hypofluorite with pyranoid and furanoid glycals

Abstract The regiospecific syn -addition of acetyl hypofluorite to glycals derived from pentopyranoses led to mixtures of stereoisomers. Stereospecific reactions occurred with furanoid glycals, the direction of addition being governed by the nature of the substituent at C-3. Whereas a benzyloxy group caused attack from the opposite, less-hindered face of the double bond, a hydroxyl group induced addition from the same side. From these reactions, 2-deoxy-2-fluoro derivatives of β- d -arabino-, α- d -ribo-, β- d -lyxo-, and α- d -xylo-pyranose as well as β- d -manno-, α- d -gluco-, α- d -ribo-, and β- d -arabino-furanose were obtainedl their 1 H-, 13 C-, and 19 F-n.m.r. data are given.

Reformatsky-Type Branching of Aldonolactones

ABSTRACT Condensation of furanoid as well as pyranoid aldonolactones with organozinc reagents obtained from different haloalkanoates and the zinc/silver-graphite surface compound gave in high yield carbon chain extended 3- or 4-ulofuranos- (or -pyranos)onates.

Chain Elongation of Aldonolactones

ABSTRACT As an alternative to the classical Reformatsky-type branching reaction of aldonolactones, ethyl trimethylsilylacetate, methyl 2-trimethylsilyl-propionate, trimethylsilylacetonitrile or alkyl 2-(trimethylsilylmethyl)-acrylates in the presence of catalytic amounts of tetra-n-butyl-ammonium fluoride can be used. The corresponding chain elongated monosaccharides are obtained in high yields.

A new, zinc-promoted synthesis of 1,4(1,5)-anhydro-2-deoxy-pent-(hex)-1-enitols (furanoid and pyranoid glycals)

Activated zinc in tetrahydrofuran efficiently converts derivatives of furanosyl and pyranosyl halides into glyacals.

Biocatalytical transformations II. Enantioselective hydrolysis of N-acetyl-fluoro-phenylalanine-ethylesters by lyophilised yeast☆

Abstract The three nuclear substituted monofluoro D-N-acetylphenylalanine-ethylesters were obtained in excellent yield via enantioselective hydrolysis of their respective racemates by use of lyophilised yeast ( Saccharomyces cerevisiae Hansen).

A short synthesis of 2-acetamido-2-deoxy-5-thio-D-glucose and -D-mannose from 5-thio-D-glucal

Starting from peracetylated 5-thio-D-glucal the title compounds were synthesized by azidonitration and subsequent hydrogenation.

Biocatalytical Transformations, III [1] Regioselective Enzymic Deacetylations of Laevoglucosane Triacetate

Abstract Several hydrolytic enzymes (porcine liver esterase, lipase from wheat germ type I, and the lipase from rhizopus javanicus) efficiently deacetylate laevoglucosane triacetate (2) with good regioselectivity into diacetylated laevoglucosane derivatives (3-5).

Synthesis and Structure of a New 1,5-Anhydro-hex-2-enitol

Treatment of methyl 4,6-O-benzylidene-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside with sodium cyanoborohydride/hydrogen chloride gives rise to a very convenient approach of 1,5-anhydro-6-O-benzyl-2,3-dideoxy-D-erythro-hex-2-enitol (2), envisaged to be a precursor for both α-D- and β-L-glycosyl compounds in the pentopyranosyl series. An X-ray analysis revealed 2 to be of space group P21 and to adopt an OH5-conformation.