A Simple Microscale Method for Determining the Relative Stereochemistry of Statine Units

A simple method to determine the relative stereochemistry of statine amino acids (γ-amino-β-hydroxyacids) by using ¹H NMR spectroscopy is described. Configurational assignment of statine units within complex natural products is possible without degradation or derivatization as the syn and anti diastereomers can be distinguished by using a combination of chemical shift and coupling constant information derived from the α-methylene ABX system. Seventy-three examples are provided, demonstrating the scope and limitations of the methodology. These examples range in complexity from simple statine units to cyclic depsipeptides, such as tamandarin B.