Auxiliary-controlled enantioselective synthesis of exo-spirotetronate subunits of Quartromicin D3

ORGN 196

Jun Qi, jqi@umich.edu, Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109-1055 and William R. Roush, roush@scripps.edu, Department of Chemistry, Scripps-Florida, 5353 Parkside Drive, RE-2, Jupiter, FL 33458.

Figure 1.

Scheme 1.

The enantioselective synthesis of the exo-spirotetronate subunits of quartromicins D3 (Figure 1) has been previously achieved by a sequence involving Lewis acid catalyzed Diels-Alder reaction. The original strategy, however, requires the installation of the hinder tertiary hydroxyl group in compound 5 (Scheme 1) after the Diels-Alder reaction. Chiral bicyclic dienophile 2 was synthesized in an effect to directly install the required hydroxyl group during the Diels-Alder reaction. The Diels-Alder reaction between dienophile 2 and acyclic (Z)-1,3-diene 1 provided cycloadduct 3 in 70% yield with 5:1 diastereoselectivity favoring the desired exo-isomer. The auxiliary unit of compound 3 was removed by lithium aluminum hydride reduction and provided diol 4 and a-hydroxyl aldehyde 5 in 65% combined yield. Both compounds 4 and 5 can be used to synthesize the exo-spirotetronate subunits of the quartromicins.

 

New Reactions and Methodology, Materials, Total Synthesis, Process R&D
8:00 PM-10:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 29 August 2005 Washington DC Convention Center -- Hall A, Sci-Mix

Division of Organic Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005