A simple microscale method for determining the relative stereochemistry of statine units

A simple method to determine the relative stereochemistry of statine amino acids (gamma-amino-beta-hydroxyacids) by using (1)H 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 alpha-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.