First total synthesis of the marine steroid alkaloid plakinamine B

The first total synthesis of the marine steroid alkaloid plakinamine B (1) was accomplished in seven steps starting from known aldehyde 3. Key steps in this synthesis are the attachment of a vinylpyridine side chain by an aldol reaction, a chemoselective reduction of a pyridinium salt to a vinyl tetrahydropyridine, and the introduction of the 3 alpha-methylamino group under Mitsunobu conditions. Plakinamine B and some of its precursors with amino or pyridinium side chains show significant antimicrobial activities. (C) 2013 Elsevier Ltd. All rights reserved.