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Solid-phase synthesis of short α-helices stabilized by the hydrogen bond surrogate approach


Stabilized α-helices and nonpeptidic helix mimetics have emerged as powerful molecular scaffolds for the discovery of protein–protein interaction inhibitors. Protein-protein interactions often involve large contact areas, which are often difficult for small molecules to target with high specificity. The hypothesis behind the design of stabilized helices and helix mimetics is that these medium-sized molecules may pursue their targets with higher specificity because of a larger number of contacts. This protocol describes an optimized synthetic strategy for the preparation of stabilized α-helices that feature a carbon-carbon linkage in place of the characteristic N-terminal main-chain hydrogen bond of canonical helices. Formation of the carbon-carbon bond is enabled by a microwave-assisted ring-closing metathesis reaction between two terminal olefins on the peptide chain. The outlined strategy allows the synthesis and purification of a hydrogen bond surrogate (HBS) α-helix in 1 week.

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Figure 1
Figure 2: Synthesis of HBS α-helices on solid phase (Knorr or Rink amide resins).
Figure 4: Reaction setup for the triphosgene-mediated coupling step.
Figure 5: Representative analytical HPLC profile of the triphosgene-mediated coupling reaction (Step 4A(xix–xxiv)).
Figure 6: Synthesis of HBS helix 5 with method B.
Figure 3: Synthesis of HBS helix 5 with method A.
Figure 7: Reaction setup for the metathesis step.
Figure 8: A representative HPLC chromatogram of the olefin metathesis reaction (Step 6).


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We are grateful for financial support from the NIH (GM073943). We also thank the National Science Foundation for equipment Grant CHE-0958457 and the NIH National Center for Research Resources (NIRR) for Research Facilities Improvement Grant C06 RR-16572.

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A.P. carried out the experiments as reported in the main paper; M.Z.M. tested the protocol; and A.P., M.Z.M., A.B.M. and P.S.A. wrote the article.

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Correspondence to Paramjit S Arora.

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Patgiri, A., Menzenski, M., Mahon, A. et al. Solid-phase synthesis of short α-helices stabilized by the hydrogen bond surrogate approach. Nat Protoc 5, 1857–1865 (2010).

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