Synlett 2011(2): 187-190  
DOI: 10.1055/s-0030-1259287
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of the Spirofungin A Core via a Domino Strategy Consisting of Olefinic Ester Ring-Closing Metathesis and Iodospiroacetalization

Jochen Neumaier, Martin E. Maier*
Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
Fax: +49(7071)295137; e-Mail: martin.e.maier@uni-tuebingen.de;
Further Information

Publication History

Received 18 October 2010
Publication Date:
23 December 2010 (online)

Abstract

Olefination of ester 26 which was obtained from acid 20 and alkenol 25 using a reduced titanium ethylidene reagent led to cyclic enol ether 28 which could be cyclized by iodospiroacetalization to the spiroacetal core of the antifungal compound spirofungin A (5).

34

In contrast to the negative result with ester 26, the Tebbe olefination did work with substrate 31 featuring an acetal protecting group for the 1,2-diol subunit. With ester 31, the Tebbe olefination only led to the acyclic enol ether 32 (Scheme  [6] ), whereas the Tebbe-Petasis reagent produced a mixture of the open and closed enol ethers 32 and 33 (open/closed = 1:2); see also Supporting Information.

Scheme 6