title: Absolute Stereochemistry of the β-Hydroxy Acid Unit in Hantupeptins and Trungapeptins.
abstract: The β-hydroxy/amino acid unit is a common structural feature of many bioactive marine cyanobacterial depsipeptides. In this study, the absolute stereochemistry of the β-hydroxy acid moieties in hantupeptins and trungapeptins were determined through their synthesis and HPLC analysis of the Mosher ester derivatives. Synthesis of two3-hydroxy-2-methyloctanoic acid (Hmoa) stereoisomers, (2S,3R)-Hmoa and (2S,3S)-Hmoa, were achieved using diastereoselective asymmetric method and the retention times of all four Hmoa isomers were established indirectly by RPLC-MS analysis of their Mosher ester derivative standards. Based on the retention times of the standards, the absolute configuration of the Hmoa unit in hantupeptin C (3) and trungapeptin C (6) was assigned as (2R,3S)- and (2S,3R)-Hmoa, respectively. The use of the Mosher's reagents, coupled with HPLC analysis, provided a viable alternative to the absolute stereochemical determination of β-hydroxy acid units in depsipeptides.
authors.forename: Deepak Kumar
authors.initials: DK
authors.lastname: Gupta
authors.forename: Gary Chi Ying
authors.initials: GC
authors.lastname: Ding
authors.forename: Yong Chua
authors.initials: YC
authors.lastname: Teo
authors.forename: Lik Tong
authors.initials: LT
authors.lastname: Tan
mesh_terms: D000458:Cyanobacteria / Q000737:chemistry*; D047630:Depsipeptides / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D047630:Depsipeptides