Final elucidation of the absolute configuration of the signal metabolite hormaomycin

Abstract

The complete absolute configuration of hormaomycin 1a has been established by HPLC and HPLC/MS experiments with appropriately derivatized 4-propylprolines, (2S,4S)-6 and (2R,4R)-6, as well as 4-(Z)-propenylprolines, cis-5 and trans-5, and also feeding experiments with enantiomerically pure samples of the deuterium-labeled 3-(2'-nitrocyclopropyl)alanine, (2S)-3,3-[D-2]15 and (2S)-2,2'-[D-2]15, and 4-(Z)-propenylproline 2',4-[D-2]-(2S,4R)-5. The latter five amino acids were prepared for the first time and allowed one to unequivocally assign the hitherto unknown absolute configurations of the last four stereocenters in hormaomycin 1a. As a bonus, some new information about the biosynthesis of this molecule has also been gathered.