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Updated: Aug 10, 2026

Chemical Inactivation of the E3 Ubiquitin Ligase Cereblon by Pomalidomide-based Homo-PROTACs
Published on: May 15, 2019
Electronically and sterically tuned trans labilization controls the substitution behaviour of cobaloximes
Mohamed S A Hamza1, Alessandro Felluga, Lucio Randaccio
1Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany.
Abstract:
The kinetics of axial water substitution by cysteine in six different cobaloximes, viz.trans-RCo(Hdmg)(2)H(2)O, where Hdmg = dimethylglyoximate, R = cyclo-C(5)H(9) (c-P), CH(3)CH(2) (Et), CH(3) (Me), C(6)H(5)CH(2) (Bz), C(6)H(5) (Ph) and CF(3)CH(2), were studied as a function of cysteine concentration, temperature and pressure. It was found that cysteine substitutes the coordinated H(2)O molecule trans to the alkyl group with second order rate constants that follow the order of reactivity: c-P > Et > Bz > Me > Ph > CF(3)CH(2). Rate and activation parameters (Deltan H(++), Delta S(++) and Delta V(++)) enable the formulation of a reaction mechanism that can account for the substitution behaviour of the investigated alkylcobaloximes. In particular, a gradual mechanistic changeover from I(d) to I is observed along the series of R groups from c-P to CF(3)CH(2).
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