Synthesis of Stapled β3-Peptides through Ring-Closing Metathesis

The first synthesis of carbon-stapled β3-peptides is reported. The precursor β3-peptides, with O-allyl β-serines located in an i/i+3 relationship, were prepared on solid phase. We show that efficient ring-closing metathesis (RCM) of these new β3-peptides proceeds smoothly either in solution or on an appropriate solid support. All products were generated with high selectivity for the E-isomer.