The absolutestereochemistry of the aglycon part of an antitumor antibiotic vicenistatin (1) was determined by a synthetic approach. Two relevant components degradatively derived from natural 1 were compared with the corresponding synthetic standards prepared from known compounds by stereochemically defined chemistry. The absolute configuration of 1 turned out to be 6S,7S,18S.
LiNH2BH3-promoted reductive opening of 8-substituted phenylglycinol-derived oxazolopiperidone lactams leads to enantiopure 4-substituted-5-aminopentanols, which are used as starting building blocks in the synthesis of the Haliclona alkaloids haliclorensin C, haliclorensin, and halitulin (formal). The starting lactams are easily accessible by a cyclocondensation reaction of (R)-phenylglycinol with racemic γ-subtituted