Synthesis of Fluorinated Macrocyclic Bis(indolyl)maleimides as Potential¹⁹F NMR Probes for Protein Kinase C

Abstract

Six macrocyclic bis(indolyl)maleimides 1-6 bearing a fluorine label on the aliphatic portion of the macrocycle have been prepared as potential fluorine NMR probes for the catalytic domain of protein kinase C. The macrocyclic bis(indolyl)maleimides such as LY333531 are reversible, ATP competitive, and isoform-selective inhibitors of protein kinase C and may thus serve to probe for subtle differences between protein kinase catalytic domains. The key stereochemical elements were put in place by a Welch aldol condensation between ethyl fluoroacetate and (R)-cyclohexylidene glyceraldehyde, which was followed by allylation of the secondary alcohol, elaboration of the alkene and ester to alcohols, and mesylation. The macrocycle was formed by slow addition of a mixture of the fluorinelabeled aliphatic dimesylate and N-methyl 2,3-bis[1H-indol-3-yl]maleimide to a suspension of cesium carbonate. Adjusting the functionality led to the six fluorine-labeled macrocyclic bis(indolyl)maleimides. These compounds retain the high potency of the parent compounds, with IC 50 values below 5 nM for the 14-membered ring compounds 1-3 and 13-90 nM for the 15-membered ring compounds 5-6. Vicinal proton-fluorine coupling constants provide an experimental parameter for determining the local macrocycle conformation.

Adenosine Mimetics as Inhibitors of NAD+-Dependent Histone Deacetylases, from Kinase to Sirtuin Inhibition

“…Alkylation of indole acetamide with the tosylate 16 , followed by condensation of 17 with methyl 4-fluoroindole-3-glyoxylate and acidic workup, led to a mixture of the triol 12e and the cyclohexylidene 12 g . The nonfluorinated compound 12f was prepared by an analogous route using methyl indole-3-glyoxylate 4 Docking results for BIM 12a.…”

Fluorine as an NMR probe for structural studies of chemical and biological systems

“…60 Observing large spin-spin couplings involving a fluorine nucleus, which were discussed earlier, is probably one of the most promising features to be exploited using 19 F labeled aliphatic amino acids. Karplus-type relationships 63 allow their exploitation for conformational analysis, 64 although no data are available for proteins yet.…”

Modulation of Mitochondrial Protein Kinase C Isozymes: A New Therapeutic Frontier?

“…However, because there is a high degree of conservation in the amino acid sequences and 3-D crystal structures of the catalytic domains of individual PKC isozymes (and many other protein kinases as well) [75] inhibition of PKC catalytic activity has yielded few drugs that can consistently discriminate between the activities of different PKC isozymes in intact cells [76][77][78]. Further, when these drugs are effective at antagonizing a PKC response their specificity must be confirmed in each cell type and often falls within a narrow window of concentration [76][77][78]. Also in the process of delivering the drugs to PKC in intact cells many chemical PKC inhibitors have non-specific cellular actions [79][80][81][82][83][84][85][86][87][88][89].…”