Synthesis 2006(23): 3997-4004  
DOI: 10.1055/s-2006-950335
PAPER
© Georg Thieme Verlag Stuttgart · New York

Rapid Combinatorial Access to Macrocyclic Ansapeptoids and Ansapeptides with Natural-Product-like Core Structures

Michiel de Greefa, Sahan Abelna, Khalid Belkasmia, Alexander Dömlingb, Romano V. A. Orrua, Ludger A. Wessjohann*a,c
a Vrije Universiteit Amsterdam, Department of Organic and Inorganic Chemistry, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
b R & D Biopharmaceuticals (formerly Morphochem AG), Am Klopferspitz 19a, 82152 Martinsried, Germany
c Address for correspondence: Leibniz Institute of Plant Biochemistry, Bioorganic Chemistry (NWC), Weinberg 3, 06120 Halle (Saale), Germany
Fax: +49(345)55821309; e-Mail: wessjohann@ipb-halle.de;
Further Information

Publication History

Received 14 October 2005
Publication Date:
02 November 2006 (online)

Abstract

14-Membered ansa-cyclopeptide alkaloids are among the most abundant natural macrocycles and thus valuable templates for diversity-oriented synthesis with biological relevance. A rapid synthesis of the core structure is conceivable by a combination of an Ugi four-component reaction with bifunctional building blocks to form the dipeptoid part, followed by a suitable macrocyclization reaction. The latter step is crucial, and an uncommon macroetherification gave the best results. The use of ammonium salts allows direct access to peptides instead of peptoids. Depending on the substitution pattern, some cyclopeptoids show planar chirality despite free rotation of the phenylene group.

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Gibson, C.; Sulyok, G.; Schmitt, J. S.; Dechantsreiter, M. A.; Haubner, R.; Hölzemann, G.; Goodman, S. L.; Kessler, H. From Proteins to Drugs: The RGD Story, The 8th Akabori Conference, Japanese-German Symposium on Peptide Science, Nagoya, Japan, 2000.

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Special issue: Peptide Libraries and Peptide Drugs, Mol. Diversity 2004, 8, 57-174

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As an example, a derivative with R4 = Ph and R3 = H decomposes within one hour, even when kept at -20 °C and stored under an argon atmosphere (see ref. 71). A similar frame-shifted approach to form the macrocyclic ring via Ugi-4CR to form moiety I resulted in dimeric structures, possibly 28-membered rings (see ref. 11).

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Rodrigues, O. E. D.; Braga, A. L.; Wessjohann, L. A. manuscript submitted.

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Orru, R. V. A.; de Greef, M.; Abeln, S.; Belkasmi, K.; Dömling, A.; Wessjohann, L. A. A Short and Flexible Route to Cyclopeptide Alkaloids, The 12th European Symposium on Organic Chemistry (ESOC 12), Groningen, The Netherlands, 2001.

72

Later, the Zhu group in their conventional SNAr approach could prove that the retro-Michael reaction is, indeed, favored (see ref. 41). In an early work, Schmidt could show for his related system that sulfide formation occurs by this approach, but ether formation not (see refs. 58, 59).

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Broad signals in the 1H NMR spectrum and the presence of additional signals in the 13C NMR spectrum suggest coexisting conformers. Spectral data refer to major isomer.