Synthesis of terminally protected (S)-β3-H-DOPA by Arndt–Eistert homologation: an approach to crowned β-peptides

Abstract Terminally protected Boc-( S )-β 3 -H-DOPA-OMe has been synthesized from l -DOPA by the Arndt–Eistert homologation procedure. During the synthesis, the side-chain catechol group was temporarily protected by benzylation. The absence of racemization was demonstrated by 19 F NMR analysis of the (+)-( R )- and (−)-( S )-α-methoxy-α-trifluoromethyl-α-phenyl-acetamide derivatives. The catechol function of Boc-( S )-β 3 -H-DOPA-OMe may be used for crown-ether formation, a step towards the construction of crowned β-peptides.