M. Cavazza et al., Colchicine red-ox chemistry revisited: Cathodic behavior and EPR observation of an intermediate radical anion, TETRAHEDRON, 55(38), 1999, pp. 11601-11608
Colchicine (1), a potently antimitotic alkaloid and useful laboratory tool
in cancer research, undergoes cathodic reduction in DMF forming an ESR-obse
rvable radical anion (1r) which is characterized by the isotropic hyperfine
coupling constants 8.9, 4.3, 0.75, 0.49 and 0.48 G for H-8, H-12, OCH3, H-
11 and H-4, respectively, and a much flattened troponoid ring. Assignments
are aided by selective deuteriation of colchicine at C-8, C-11 and COCH3, a
s well as by spectral simulation and ab initio calculations of electron spi
n densities. Whether the colchicine radical anion may exist in nature is al
so discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.