Abstract
Starting from natural proline, a practical chirospecific synthesis of spirocyclic β-lactams of type 2 is described when a methylene moiety showing minimal steric demand is employed as a constraint element for adjusting the dihedral angle Ψ(i + 1). Employing the concept of self-reproduction of chirality, C-formylation of the oxazolidinone 5 afforded the key intermediate 7 taking advantage of an intermediate protection of the bridging element as a vinyl moiety. NMR- and IR-based conformational studies clearly indicated that spiro-β-lactams of type 2 can serve as efficient β-turn nucleators.

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