Practical Asymmetric Syntheses of All Four 2,3-Methanoleucine Stereoisomers

Abstract All four stereoisomers of the 2,3-methanoamino acids BOC-E-cyclo-Leu and BOC-Z-cyclo-Leu were prepared from the optically active diol 4 (and its enantiomer) derived from valine. The challenges associated with introducing protected amine functionalities cis to the side chain were overcome by using the vinylogous malonate synthon, dimethyl gluconate.