Liu D, Acharya HP, Yu M, Wang J, Yeh VSC, Kang S, Chiruta C, Jachak SM, Clive DLJ. Total synthesis of the marine alkaloid halichlorine: development and use of a general route to chiral piperidines.
J Org Chem 2009;
74:7417-28. [PMID:
19739615 DOI:
10.1021/jo901481n]
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Abstract
The total synthesis of the marine alkaloid halichlorine is described, based on an approach that involves constructing the fully substituted asymmetric center at an early stage. The five-membered ring is formed by 5-exo-trig radical cyclization and the unsaturated six-membered ring by a process that formally represents a sequential combination of conjugate addition and S(N)2' displacement-a method that is general for making bicyclic compounds with nitrogen at a ring fusion position. A formal synthesis of (+)-halichlorine is also reported, based on the development of a general method for preparing optically pure piperidines. The key step of this method, which was used to make one of our intermediates, is the Claisen rearrangement of a 4-vinyloxy-3,4-dihydro-2H-pyridine-1-carboxylic acid benzyl ester. Such O-vinyl compounds are easily generated in situ from the corresponding alcohols, which are themselves readily assembled from serine and terminal acetylenes.
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