Synthetic Plan Research Articles

Communication: FuranosideC-Glycosides from anO-Methyl Pyranoside: An Unexpected ß-Hydroxy-1,3-Dithiane Rearrangement

In the course of our investigations on the synthesis of enantiomerically pure anthracycline antibiotics by incorporation of chiral building blocks we prepared the O-methyl 3-deoxy-2-C-ethylribopyranoside 1.1 The further synthetic plan required the conversion of 1 to the dithioacetal 2 followed by glycol cleavage to a partially protected 1,4-dialdehyde for coupling experiments to leucoquinizarine in a Marschalk reaction. However, the reaction sequence failed1 and optically active rhodomycinone had to be synthezised in a different way.2 A reinvestigation of the synthesis revealed that the thioacetalization of 1 using the acidic conditions recommended by Corey et al.3 did not yield the usual open chain dithioacetal 2 but rather three new unexpected products. The less polar fraction was identified by 1H and 13C NMR as tetrahydrofuran derivative 3a with the dithiane ring in a ß-orientation. The solid polar fraction (12%) consisted of a nonseparable 1:2.2 mixture of the epimeric deoxygenation products 4/5.

A síntese de um furano-guiano

A síntese de lactonas sesquiterpênicas do tipo guaiano é de interesse devido as atividades biológicas associadas às estruturas complexas deste grupo de produtos naturais. Planejou-se a sua síntese a partir de monoterpenos abundantes isolados de óleos essenciais brasileiros. Assim p-ment-l-eno foi transformado em 2-bromo-6-isopropil-3-metil-ciclohept-2-enona por adição de dibromocarbeno, expansão de anel com rearranjo usado AgNO3, e finalmente oxidação com clorocromato de piridinio. Redução quimioseletiva do bromo com zinco em ácido acético e alquilação termodinâmica em α,β-insaturada. Tratamento com ácido sulfúrico concentrado efetuou hidrólise e desidratação a um furano anelado a um ciclohepteno de estrutura de um oxa-guaiano.

ChemInform Abstract: Synthetic Studies Relating to the C1‐C9 “Eastern” Half of Rosaramicin.

Abstract A pyranodisic homologation approach to the “eastern half” of rosaramicin is described. The synthetic plan calls for two one-carbon chain extensions, but these occur at “off-template” sites where asymmetric centers are neither destroyed nor created. However, these one-carbon displacements pose special unexpected difficulties and procedures for overcoming these are described.

Synthetic studies relating to the C1–C9 “Eastern” Half of Rosaramicin

A pyranodisic homologation approach to the “eastern half” of rosaramicin is described. The synthetic plan calls for two one-carbon chain extensions, but these occur at “off-template” sites where asymmetric centers are neither destroyed nor created. However, these one-carbon displacements pose special unexpected difficulties and procedures for overcoming these are described.

The role of symmetry in synthetic analysis. The concept of reflexivity

Molecular symmetry can complicate or simplify a synthetic problem (conditions are given for each case); however, symmetry in a synthesis graph (synthetic plan) is always a simplifying factor.

Synthese assistee par ordinateur de la phosphacarnegine-I Etablissement du plan de synthese avec l'aide de pascop

Using a retrosynthetic analysis of the target structure 1, the chemist-PASCOP team has developed a synthetic plan for this new phosphine.

Synthese Assistee Par Ordinateur De La Phosphacarnegine

Abstract A synthetic plan for the phosphacarnegine 1 established with a computer program (PASCOP) was executed. Although some pathways were not appropriate, two successful routes giving 1 in a yield of 15 % and 4.5 % respectively are described. Limits of PASCOP are discussed.

A Third Dimension for Science Policy

1. Starr Roxanne Hiltz, Murray Turoff, Network Nation: Human Communications Via Computer (Reading: AddisonWesley, 1978). 2. Susan Sparta Cherry, Telereference: New TV Information System, American Libraries, Vol. II, February 1980, pp. 94-98; and Michael Tyler, Videotext, Prestel and Teletext: Economics and Politics of Some Electronic Publishing Media, Telecommunications Policy, March 1979. 3. Richard Hutton, Bio-Revolution: DNA and the Ethics of Man-Made Life (New York: New American Library, Inc., 1978). 4. Marjorie Sun, Making Interferon: Gains Come Slowly, Science, Vol. 210, November 7, 1980, p. 618; and Hutton, pp. 114-115. 5. Ibid., pp. 114-115 (Hutton only). 6. Ibid., p. 115 (Hutton only). 7. Nicholas Wade, Ultimate Experiment (New York: Walker and 1977). 8. of the Bottle, Progressive, August 1980, p. 8, vol. 44, no. 8. Nicholas Wade, Supreme Court to Say if Life is Patentable, Science, Vol. 206, November 9, 1979, p. 664. 9. Peter J. Schuyten, The Solution: Rub Is in the Cost, New York Times, July 15, 1979. 10. See Mitchell Moss, Cable Television: A Technology for Citizens, University of Detroit Journal of Urban Law, Vol. 53, No. 3, Spring 1978. 11. Nicholas Wade, op. cit. 12. Synthetic Fuel Plan: A Boon for Business, New York Times, August 25, 1980. 13. Robert D. Hershey, Jr., Blessing or Boondoggle? $88 Billion Question for Fuels, New York Times, September 21, 1980. 14. Nicholas Wade, Ultimate Experiment, pp. 127-144. 15. Cloning Gold Rush Turns Basic Biology into Big Business, Science, Vol. 208, May 16, 1980, p. 688. 16. Nicholas Wade, Gene Splicing Company Wows Wall Street, Science, Vol. 210, October 31, 1980, p. 506. 17. Michael Knight, Harvard Rules Out Role for Now in Genetic Engineering Company, New York Times, November 1980. 18. Anne C. Roark, Drug Company Challenges UCLA over Ownership of Human Gene, Chronicle of Higher Education, Vol. 21, No. 7, October 6, 1980. 19. Robert D. Hershey, Jr., op. cit. 20. I am obligated to my Maxwell colleague, Professor Edwin Bock, for the term decisions-in-the-making.

ChemInform Abstract: COMPUTER‐ASSISTED SYNTHETIC ANALYSIS. THE IDENTIFICATION AND PROTECTION OF INTERFERING FUNCTIONALITY IN MACHINE‐GENERATED SYNTHETIC INTERMEDIATES

ChemInform Abstract: COMPUTER‐ASSISTED SYNTHETIC ANALYSIS. THE IDENTIFICATION AND PROTECTION OF INTERFERING FUNCTIONALITY IN MACHINE‐GENERATED SYNTHETIC INTERMEDIATES

Computer-assisted synthetic analysis. The identification and protection of interfering functionality in machine-generated synthetic intermediates

Computer-assisted synthetic analysis. The identification and protection of interfering functionality in machine-generated synthetic intermediates

A stereospecific synthetic route to campherenone, campherenol, epicampherenone, β-santalene, epi-β-santalene, ylangocamphor, copacamphor, sativene, and copacamphene

A simple and efficient synthetic route to either enantiomeric form of campherenone and epicampherenone [the epimeric 1,7-dimethyl-7-(4-methylpent-3-enyl)norbornan-2-ones], β-santalene and epi-β-santalene [2-methyl-3-methylene-2-(4-methylpent-3-enyl)norbornanes], and the perhydro-1,4-methanoindene derivatives copacamphor, copacamphene, ylagocamphor, and sativene is described. The simplicity of the synthetic route is due to the application of a general synthetic plan and the development of a new process for effecting direct 8-substitution of camphor.

General methods for the construction of complex molecules

Abstract

Synthetic Rubber Plant Disposal Plan Submitted

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