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Journal of the American Chemical Society
was isolated from the growth, nevertheless, compound 9 previously established. By utilizing
a
unique non-
1
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8
was identified via LC-MS/MS analysis (Figure S11). Due to
the instability and low yield of 9, purification and charac-
terization were not attempted. Instead we opted to use
our developed methodology to derivatize 9 using succin-
imidyl ester 2. Production of 9a was confirmed via LC-
MS/MS analysis of the reaction mixture (Figure S12), and
the material was then purified. Compound 9a was isolat-
ed in limited quantity (< 1 mg) with significant impurities.
MS/MS fragmentation of 9a was entirely consistent with
enzymatic process within the jadomycin biosynthetic
pathway, S. venezuelae likely produces many jadomycin
analogues under stress conditions in an ecological setting.
ASSOCIATED CONTENT
Supporting Information
Experimental procedures, material, supporting figures, NMR-
spectra and additional data are described. This material is
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available
free
of
charge
via
the
Internet
at
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the data for 1a, and the H-NMR spectra of both com-
pounds were also comparable (Figure S63), suggesting the
presence of an eight-membered ring containing deriva-
tive.
AUTHOR INFORMATION
Corresponding Author
* Tel: +1 902 494 7159; david.jakeman@dal.ca
Biological Activity. Compounds 1a, 1c, 1d and 1f were
selected by the National Cancer Institute for testing
against their 60 DTP human tumor cell line one-dose
screen. In contrast to the previous jadomycins bearing
five-membered oxazolone rings, cytotoxicity of the com-
pounds was limited despite their ability to invoke Cu(II)-
mediated DNA damage (Figure S15). This suggests the
importance of the five-membered oxazolone ring for anti-
tumor bioactivity over the new eight-membered ring sys-
tem.15 The expanded ring system also leads to an attenua-
tion of the antimicrobial properties normally associated
with the jadomycins. Lack of appreciable cytotoxicity un-
der ambient conditions is desirable for photodynamic
applications that employ light-responsive agents, so rep-
resentative compounds 1a-1d were tested for their light
induced antibacterial activity against Streptococcus mu-
tans as a model system (Figure S16). All four compounds
exhibited photodynamic inactivation (PDI) of bacteria, in
the order 1a>1b~1c>1d. However, they do not appear to
act via a DNA photodamaging pathway, given that gel
electrophoretic mobility-shift assays revealed minimal
DNA photocleavage under comparable conditions (Figure
S14). This unexpected PDI activity is a unique feature of
the eight-membered ring system.
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version
of the manuscript.
Funding Sources
We thank NSERC, CIHR, and CHRP for financial support of
this research.
ACKNOWLEDGMENT
We would like to thank Dr. Nadine Merkley and Ian Burton
at the NRC-IMB for their NMR support on the 700 MHz in-
strument and Xiao Feng for acquisition of HRMS data. We
would also like to thank Stephanie Forget for her help edit-
ing the manuscript.
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CONCLUSION
We have successfully isolated and characterized the
amine containing jadomycin Oct (1) and identified it as
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having L-ornithine incorporated as
a unique eight-
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membered ring system. This sheds light on the potential
promiscuity of the spontaneous amino acid incorporation
step of jadomycin biosynthesis and how it could be fur-
ther exploited. Additionally, we successfully synthesized
and utilized a group of activated carboxylic acids to semi-
synthetically derivatize the free amine of 1, producing a
small library of jadomycin amides that act as antimicrobi-
al phototoxins (1a-1f), all containing the unique eight-
membered ring scaffold. These compounds are the first
examples of jadomycins containing eight-membered het-
erocyclic rings. Additionally, the isolation of jadomycin
AVA (8) unequivocally confirms the presence of the
eight-membered ring. The ability to form fully cyclized
compounds using amino groups other than the α-amino
group of amino acids suggests the structural diversity
associated with the jadomycins may be much larger than
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