Fortschritte der Chemie organischer Naturstoffe / Progress by Dr. J. W. Daly, Prof. Dr. D. Ferreira, Dr. St. J. Gould,

By Dr. J. W. Daly, Prof. Dr. D. Ferreira, Dr. St. J. Gould, Prof. Dr. E. Haslam, Dr. D. J. Robins, Prof. Dr. D. G. Roux, Prof. Dr. St. M. Weinreb (auth.), Dr. W. Herz, Prof. Dr. H. Grisebach, G. W. Kirby Sc. D. (eds.)

The chemistry of condensed tannins has hitherto represented a comparatively unattractive and for this reason overlooked zone of research; one during which the burden of study attempt concerned is perpetually disproportionate to the consequences accomplished, during which the partaking colleges more often than not confine their method of particular molecular species, and during which as but no consensus has been reached concerning most probably precursors. the issues which beset these engaged during this box characterize a mixed functionality of the irregular complexity of the gradational variety of oligomers of accelerating mass and affinity for substrates which typify so much extracts wealthy in tannins, and the ensuing challenge in their isolation and purification, the excessive chirality of tannin oligomers, the necessity to deal with the phenomenon of dynamic 'rotational isomerism approximately interflavanoid bonds within the IH n.m.r. spectral interpretation in their derivatives, the inability of detailed wisdom concerning the issues of bonding at nucleophilic centres, and the most obvious boundaries of a hitherto predominantly analytical method. The final of those displays the necessity for a basic approach to synthesis which allows unambiguous facts of either constitution and absolute configuration additionally at greater oligomeric degrees. With those targets in brain we initiated a only man made technique according to the basis that flavan-3,4-diols as resource of electrophilic flavanyl-4-carbocations, and flavan-3-0Is as nucleophiles (cf 1,2) signify the leading initiators of a means of repetitive condensation within which the fast items additionally signify the sequent nucleophilic substrates.

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By Dr. J. W. Daly, Prof. Dr. D. Ferreira, Dr. St. J. Gould, Prof. Dr. E. Haslam, Dr. D. J. Robins, Prof. Dr. D. G. Roux, Prof. Dr. St. M. Weinreb (auth.), Dr. W. Herz, Prof. Dr. H. Grisebach, G. W. Kirby Sc. D. (eds.)

The chemistry of condensed tannins has hitherto represented a comparatively unattractive and for this reason overlooked zone of research; one during which the burden of study attempt concerned is perpetually disproportionate to the consequences accomplished, during which the partaking colleges more often than not confine their method of particular molecular species, and during which as but no consensus has been reached concerning most probably precursors. the issues which beset these engaged during this box characterize a mixed functionality of the irregular complexity of the gradational variety of oligomers of accelerating mass and affinity for substrates which typify so much extracts wealthy in tannins, and the ensuing challenge in their isolation and purification, the excessive chirality of tannin oligomers, the necessity to deal with the phenomenon of dynamic 'rotational isomerism approximately interflavanoid bonds within the IH n.m.r. spectral interpretation in their derivatives, the inability of detailed wisdom concerning the issues of bonding at nucleophilic centres, and the most obvious boundaries of a hitherto predominantly analytical method. The final of those displays the necessity for a basic approach to synthesis which allows unambiguous facts of either constitution and absolute configuration additionally at greater oligomeric degrees. With those targets in brain we initiated a only man made technique according to the basis that flavan-3,4-diols as resource of electrophilic flavanyl-4-carbocations, and flavan-3-0Is as nucleophiles (cf 1,2) signify the leading initiators of a means of repetitive condensation within which the fast items additionally signify the sequent nucleophilic substrates.

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KOTTENHAHN: (- )-Chebulsaure aus Aigarobilla. Liebigs Annalen 729, 249 (1969). 93. SHIPCHANDLER, M. , C. A. PETERS, and C. D. HURD: Syntheses of Gallic Acid and Pyrogallol. J. Chern. Soc. (Perkin I) 1975, 1400. 94. STOTHERS, J. : Carbon-13 NMR Spectroscopy. London and New York: Academic Press. 1972, 197. 95. , and E. HASLAM: Gallotannins Part 15. Some Observations on the Structure of Chebulinic Acid and its Derivatives. J. Chern. Soc. (C) 1967, 2381. 96. , M. A. IYENGAR, O. SELIGMAN, H. I. EL-SISSI, N.

M. SCHMIDT, and 1. HEROK: Die Konstitution und Konfiguration des Corilagins. Liebigs Annalen 587, 67 (1954). 78. SCHMIDT, O. : Natiirliche Gerbstoffe, in: Moderne Methoden der Pflanzenanalyse, Vol. 3: Paech and Tracey, p. 517. Berlin-Gottingen-Heidelberg: Springer. 1955. 79. SCHMIDT, O. , and E. KOMAREK: Valoneasaure. Liebigs Annalen 591, 156 (1955). 80. SCHMIDT, O. : Gallotannine und Ellagen-Gerbstoff. Fortschritte der Chemic organischer Naturstoffe, Bd. XIII, p. 570. Wien: Springer. 1956. 81.

CULVENOR, C. : The Conformation of Esters and the "Acylation Shift" NMR Evidence from Pyrrolizidine Alkaloids. trahedron Letters 1966, 1091. 109. : Chemistry of Vegetable Tannins. London and New York: Academic Press. 1966. 110. SCHMIDT, O. , E. KOMAREK, and H. RENTEL: Synthese der Octamethylvaloneasaure. Liebigs Annalen 602, 50 (1957). 111. SCHMIDT, O. , and K. BERNAUER: Brevifolin und Bervifolincarbonsaure. Liebigs Annalen 588, 211 (1954). (Received November 24, 1980) The Direct Biomimetic Synthesis, Structure and Absolute Configuration of Angular and Linear Condensed Tannins By D.

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