Paper
Organic & Biomolecular Chemistry
Acknowledgements
We wish to thank the EPSRC for a DTA studentship (ZJA), Dr
Lijiang Song for NMR data for the isolated naturally derived
azolemycins and Prof. Greg Challis for useful discussions.
Notes and references
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Scheme 5 (i) DAST, CH2Cl2 then DBU, pyr., CCl4, MeCN, 0 °C to rt,
72 h, 89%; (ii) LiOH, H2O, THF, CH2Cl2, 67%; (iii) L-Ile-OMe·HCl, EDCI,
cat. HOBt, NMM, EtOH, 0 °C to rt, 18 h, 54%; (iv) MeOH, AcCl, rt, 2 h;
then 22, EDCI, cat. HOBt, NMM, EtOH, 0 °C to rt, 18 h, 62%; (v) SO3·pyr.,
NEt3·DMSO, CH2Cl2, 0 °C, 6 h, 72%; (vi) NH2OH·HCl, pyridine, MeOH,
CHCl3, rt, 18 h, 33%.
As well as the obvious shift of the peak corresponding to C32
from 120.2 ppm in 1 to 138.31 ppm in 30, the peaks corres-
ponding to the other carbons of azole C, and those immediately
surrounding it, were shifted significantly. In particular, in the
thiazole 1 the peak corresponding to B ring carbon C11, occurs
at 130.9 ppm, but in the oxazole 30 the C11 peak appears at
125.7 ppm. This large difference in chemical shift may facilitate
the identification of the relative positions of oxazoles and
thiazoles in new polyazole natural products (Fig. 3).
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These syntheses produced azolemycin A and C and the
tetraoxazole analogue 30, for initial biological testing.1 We are
continuing assays in this area.
Fig. 3 Numbering for azolemycin A, 1 and tetraoxazole 30.
Org. Biomol. Chem.
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