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Synthesis 1996; 1996(11): 1336-1340
DOI: 10.1055/s-1996-4388
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An Improved Method for the Preparation of N-Unsubstituted 1,4,5,6-Tetrahydrocyclopenta[b]pyrroles: Synthesis of an Azaprostacyclin Analogue and Its 7-Cyano Derivative

Brigitte Rousseau, Fredy Nydegger, Albert Gossauer* , Bärbel Bennua-Skalmowski, Helmut Vorbrüggen
  • *Institut für Organische Chemie der Universität, Ch. du Musée 9, CH-1700 Fribourg, Switzerland, Fax +41(37)299739; E-mail Albert.Gossauer@unifr.ch
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Publication Date:
31 December 2000 (online)

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Paal-Knorr cyclization of 2-acetonylcyclopentanone derivatives can be carried out most efficiently by reaction with hexamethyldisilazane (HMDS) when the reagents are previously adsorbed on alumina. By this procedure, the unstable pyrroloprostacyclin derivative rac-6a has been synthesized in 66% yield from racemic 6-oxoprostaglandin E1 (rac)-5b. In order to obtain less sensitive pyrroloprostacyclin derivatives, rac -6a has been transformed into the stable nitriles rac -7a and rac -7b by cyanation of the pyrrole ring with chlorosulfonyl isocyanate in the presence of triethylamine and subsequent cleavage of the protecting groups, respectively.

Paal-Knorr synthesis of pyrroles - Al2O3 catalysis - hexamethyldisilazane - potential antianaphylactic agents