Cyclobutyl-Containing Rigid Analogues of Threonine: Synthesis and Physical Chemical Properties

摘要

Hitherto unknown cis- and trans-1-amino-3-hydroxy-3-methylcyclobutanecarboxylic acids were synthesized in multigram scale. The obtained compounds can be considered as achiral conformationally restricted analogues of threonine with fixed spatial orientation of functional groups. pK(a) values are noticeably different for both amino acids. According to the X-ray data the cydobutane rings in both compounds are almost planar (the corresponding torsion angles are below 7 degrees).