Organic Letters 2006-01-05

Synthesis of the N-acetylcysteamine thioester of seco-proansamitocin.

Thomas Frenzel, Marco Brünjes, Monika Quitschalle, Andreas Kirschning

Index: Org. Lett. 8(1) , 135-8, (2006)

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Abstract

[structure: see text] The enantioselective total synthesis of the N-acetylcysteamine thioester of seco-proansamitocin, a key biosynthetic intermediate of the highly potent antitumor agent ansamitocin, is described, which twice utilizes the Nagao acetate aldol reaction, as well as an indium-mediated alkynylation of a benzyl bromide followed by carboalumination. The key step is a Heck reaction between two terminal alkenes for merging the two major fragments.