Intramolecular [3 + 2]-Hetero-Annulation of Allylsilanes with 1,3-Cyclohexanediones and its Application in the Synthesis of Hexacyclic Hopane Triterpenes

Dieter Schinzer; Norbert Müller; Axel K. Fischer; Jan W. Prieß

doi:10.1055/s-2000-7132

Synlett 2000; 2000(9): 1265-1268
DOI: 10.1055/s-2000-7132

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Intramolecular [3 + 2]-Hetero-Annulation of Allylsilanes with 1,3-Cyclohexanediones and its Application in the Synthesis of Hexacyclic Hopane Triterpenes

Dieter Schinzer^* , Norbert Müller, Axel K. Fischer, Jan W. Prieß

^*Chemisches Institut der Otto-von-Guericke-Universität, Universitätsplatz 2, D-39106 Magdeburg, Germany; Fax (+49)3 91-6 71 22 23; E-mail: Dieter.Schinzer@vst.uni-magdeburg.de

Abstract

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In this letter we describe the intramolecular [3 + 2]-hetero-annulation of allylsilanes with 1,3-cyclohexanediones followed by sila-Wagner-Meerwein shift. The new synthesis of the cyclization precursors offers the advantage to vary the silyl terminator at the end of the synthetic sequence. The Lewis acid-mediated cyclization was optimized for the synthesis of the D-E-F-subunit of hexacyclic hopane triterpenes. The AB-fragment of these terpenes was synthesized in one step via regioselective ring opening of commercially available (-)-ambroxide.

cyclizations - Lewis acids - silicon - terpenoids - total synthesis

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