Download Artificial Small-Molecule Peptide Synthesizer

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
+
+
i) Cu(MeCN)4PF6,TentagelTM TBTA,
CH2Cl2:tBuOH=1:1
ii) AgNO3, acetone:H2O=4:1,
43% over, 2 steps
Building block synthesis-strand bearing amino acid 3
+
Building block synthesis—rotaxane formation
Cu(MeCN)4PF6,
CH2Cl2:tBuOH=1:1
7d, 32% yield
Building block synthesis—rotaxane formation 2
PhNH2(cat.), DMSO:MES-buffer=3:1
90% yield
Small-molecule machine—ready, go!
Reaction condition: 60oC under microwave heating, MeCN:DMF=3:1
N,N-diisopropylethylamine, tris(2-carboxyethyl)phosphine, 36h
Identification of the products
Peptide synthesis occurs overwhelmingly within the confines
of the molecular machine
• 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
Recent progress
• The yield of rotaxane was increased through a change of
sequence in the synthetic route
• A seven peptide containing chain was synthesized
Leigh,D.A. et al. JACS, 2014. ASAP
Discussion
• 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 2
• 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 3
• 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 4
• The scope of amino acid substrate was not
demonstrated. There might be problems with certain
amino acids such as Lys, Arg, Cys
Summary
• 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
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