The potent anthelminticcyclooctadepsipeptidePF1022A was synthesized by a series of fragment condensations starting from the known (S)-2-chloropropanoic acid and (S)-2-chloro-3-phenylpropanoic acid in eleven steps with a total yield of 13%. Noteworthy is the excellent yield of the BOP-Cl mediated lactamization reaction of the linear precursor 17 leading to the 24-membered macrocycle.
N-alkylation of unprotected aminoacids. The catalytic system gives excellent selectivity toward monoalkylated α-amino acids and a high degree of retention of stereochemistry. A wide range of unprotected nonnatural aminoacids have been prepared. These compounds represent an array of building blocks that could be used for the direct synthesis of peptidomimetics. The synthesis of amino-acid-based surfactants
The first structure-activity relationships of the anthelmintic cyclooctadepsipeptide PF1022A have been established via a systematic exchange of the leucine residues by a series of related N-alkylated amino acids. The data presented strongly suggest that (L)-N-methyl-leucine is crucial for high in vivo activity. (C) 1998 Elsevier Science Ltd. All rights reserved.