Optically Active N- and C-Terminal Building Blocks for the Synthesis of Peptidyl Olefin Peptidomimetics

Peptidyl olefin peptidomimetics serve as biologically active compounds or as intermediates for other peptidyl isosteres. The N-terminal side of the C=C bond could be easily prepared in an optically pure form from alpha-amino acids. Synthesis of C-terminal building blocks in an optically pure form is more challenging. We developed a chemoenzymatic stereoselective approach to such optically active C-terminal building blocks to be assembled into peptidyl olefins by a variety of reactions. They include an electrophilic aldehyde and nucleophilic sulfone, phosphonium salt, phosphonate, and diselenide. Key enzymatic hydrolysis of prochiral diesters to the corresponding hydroxy esters introduces optical activity. The sequence of the subsequent chemical reactions, either protection-hydrolysis-functionalization or functionalization-hydrolysis-protection, determines the absolute stereochemistry of the final building blocks.