Article

Asymmetric synthesis of all the known phlegmarine alkaloids.

Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.
The Journal of Organic Chemistry (Impact Factor: 4.56). 11/2010; 75(24):8564-70. DOI: 10.1021/jo1019688
Source: PubMed

ABSTRACT The asymmetric synthesis of all four of the known natural phlegmarines and one synthetic derivative has been accomplished in 19-22 steps from 4-methoxy-3-(triisopropylsilyl)pyridine. Chiral N-acylpyridinium salt chemistry was used twice to set the stereocenters at the C-9 and C-2' positions of the phlegmarine skeleton. Key reactions include the use of a mixed Grignard reagent for the second N-acylpyridinium salt addition, zinc/acetic acid reduction of a complex dihydropyridone, and a von Braun cyanogen bromide N-demethylation of a late intermediate. These syntheses confirmed the absolute stereochemistry of all of the known phlegmarines.

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May 21, 2014