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DOI: 10.1055/s-2007-992509
Synthesis of (-)-Membrenone B
Contributor(s):Philip Kocienski, Zofia KomstaUniversity of Saskatchewan, Saskatoon, Canada
The Thiopyran Route to Polypropionates: Enantioselective Synthesis of Membrenone B from Racemic Fragments
J. Org. Chem. 2007, 72: 7805-7808
Publication History
Publication Date:
23 January 2008 (online)
Key words
organocatalysis - aldol reaction - dynamic kinetic resolution
Significance
(+)-Membrenone B was isolated from the skin of a Mediterranean mollusc Pleurobranchus membranaceus. It is a feeding deterrent for some of its natural predators. This concise synthesis focuses on two aldol reactions, using thiopyrans to control enolate geometry. A similar strategy was used in the synthesis of erythromycin: R. B. Woodward et al. J. Am. Chem. Soc. 1981, 103, 3210.
Comment
Enantiomerically enriched D was prepared on a multigram scale by an aldol reaction of A and B (the reaction proceeds with dynamic kinetic resolution) followed by isomerization. Compound D undergoes a second, highly diastereoselective aldol reaction with racemic A to give E as a mixture of three out of eight possible isomers. The diastereoisomeric mixture was used in the next step without separation.