Artificial small-molecule peptide synthesizer

Leigh, D.A. et al. Science. 2013,339,189-193

Lingbowei Hu

Burke Group Literature Seminar

4.12.2014

Framework of the small-molecule machine

Background—nonribosomal peptide synthesis

PCP: peptidyl carrier protein

Chem. Rev. 2005,105,715-738

Background—conventional solid-phase peptide synthesis

Chem.Rev. 2000,100,2091-2157

Framework of the small-molecule machine

Building block synthesis-strand bearing amino acid

Building block synthesis-strand bearing amino acid 2

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i) Cu(MeCN)4PF6,TentagelTM TBTA,CH2Cl2:tBuOH=1:1

ii) AgNO3, acetone:H2O=4:1, 43% over, 2 steps

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Building block synthesis-strand bearing amino acid 3

Building block synthesis—rotaxane formation

Cu(MeCN)4PF6,CH2Cl2:tBuOH=1:17d, 32% yield

Building block synthesis—rotaxane formation 2

PhNH2(cat.), DMSO:MES-buffer=3:190% yield

Small-molecule machine—ready, go!

Reaction condition: 60oC under microwave heating, MeCN:DMF=3:1N,N-diisopropylethylamine, tris(2-carboxyethyl)phosphine, 36h

Identification of the products

• Neither peptide with different sequences nor with more or less than one Phe, Leu or Ala residue was found

• In a control experiment where nonthreaded strand and macrocycle were used, several products were found but no desired product was detected

Peptide synthesis occurs overwhelmingly within the confines of the molecular machine

• The yield of rotaxane was increased through a change of sequence in the synthetic route

• A seven peptide containing chain was synthesized

Recent progress

Leigh,D.A. et al. JACS, 2014. ASAP

• Demonstrated more or less the potential of small-molecule machines

• The design could be employed in other types of reactions

• Application?

• Long reaction time due to the movement of the macrocycle, low efficiency, rotaxane building is labor intense

-12h per amide bond, 30% yield (53%yield in subsequent work)

-Ribosome:15 to 20 amide bonds per second

-Conventional solid-phase peptide synthesis: 2 to 4 hours per bond

Discussion

• The first three Cys-Gly-Gly is required for successful synthesis

• The size of the oligopeptide chain is restrict by the design of the machine

Discussion 2

• Strand has to be synthesized separately for different peptides, combined in desired sequence manually and the sequence information is lost after it is translated into the product

Discussion 3

• The scope of amino acid substrate was not demonstrated. There might be problems with certain amino acids such as Lys, Arg, Cys

Discussion 4

• The first small-molecule peptide synthesizer which resembles peptide synthesis of ribosome was synthesized and proved to work

• Up to 4 amino acids can be attached in specific sequence to an certain 3-amino-acid peptide chain, with a rate of approximately 12h per amino acid

• Although inspiring, the further development of this system faces a lot restrictions and challenges

Summary

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