Asymmetric synthesis of (-)-(S,S)-homaline

The asymmetric synthesis of (-)-(S,S)-homaline was achieved in 8 steps from commercially available starting materials using the diastereoselective conjugate addition of the novel lithium amide reagent lithium (R)-N-(3-chloropropyl)-N-(α-methyl-p-methoxybenzyl)amide to methyl cinnamate to install the correct stereochemistry. Subsequent functional group manipulation of the resultant β-amino ester and Sb(OEt) 3- mediated macrolactamisation was followed by homodimerisation to give (-)-(S,S)-homaline in 18% overall yield, representing the first asymmetric, and by far the most efficient synthesis of this natural product reported to date. © 2011 Elsevier Ltd. All rights reserved