Download PDF
Synthesis 2009(5): 779-786  
DOI: 10.1055/s-0028-1083361
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Enantioselective Synthesis of Flavan-3-ols Using a Mitsunobu Cyclization

Karsten Krohn*a,, Ishtiaq Ahmeda, Markus Johnb
a Department of Chemistry, University of Paderborn, Warburger Straße 100, 33098 Paderborn, Germany
Fax: +44(5251)603245; e-Mail: k.krohn@uni-paderborn.de;
b Macherey-Nagel GmbH & Co. KG, Neumann-Neander-Straße 6-8, 52355 Düren, Germany
Further Information

Publication History

Received 9 September 2008
Publication Date:
11 February 2009 (online)

    Permissions and Reprints All articles of this category

Abstract

The synthesis of four flavan-3-ols with different substitution patterns and electron densities has been achieved in high stereo- and regioselectivity by a one-step Mitsunobu reaction from the corresponding diols, which were prepared by enantioselective Sharpless dihydroxylation of suitable olefins. The six-membered flavan-3-ols were the only cyclization products and the theoretically possible formation of five-membered rings during the Mitsunobu cyclization was not observed. The flavanols are important starting materials for the synthesis of dimers such as the procyanidins or other coupling products such as the flavan part of the potent DNA polymerase β inhibitor myristinin A. The enantioselectivities of both the Sharpless dihydroxylation and the Mitsunobu cyclization steps were monitored by chiral HPLC.

Key words

myristinin A - Sharpless dihydroxylation - flavanol synthesis - Mitsunobu reaction