Zinc metal organomercurials

Latent forms of MMPs can be activated by mechanisms which cause the dissociation of the intramolecular complex between a particular cysteine residue and the required zinc metal ligand (a complex that blocks the active site) [47], This occurs because the cysteine of the latent enzyme is coordinated to the active site in a particular way that blocks the MMP active site. Collectively, the activation of MMPs occurs through a process which has been termed the cysteine-switch . Activators of the MMPs include proteases (e.g. plasmin), conformational perturbants (SDS, NaSCN), heavy metals and organomercurials (e.g. Au(I) compounds, Hg(II)), oxidants (e.g. OC1-), disulfide compounds (e.g. GSSG) and sulfhydryl alkylating agents (e.g. V-ethylmaleimide) [47 and refs, therein]. 

In 1864, Frankland discovered the transmetallation reaction between diorganomercurials and zinc metal (equation 9). It is generally applicable when the organomercury compounds are available and when it is necessary to prepare absolute salt free diorganozinc compounds. 

The alkyls may also be prepared, and the diaryls most conveniently obtained, by the reaction of zinc metal with an organomercury compound ... 

As shown in eqs. (5.3)-(5.7), organozinc compounds are easily prepared by the reactions of zinc compounds or zinc metal with organometallic compounds such as Grignard reagents, organoaluminum compounds, organomercury compounds and organolithium compounds [12,13,18]. 

Support-bound transition metal complexes have mainly been prepared as insoluble catalysts. Table 4.1 lists representative examples of such polymer-bound complexes. Polystyrene-bound molybdenum carbonyl complexes have been prepared for the study of ligand substitution reactions and oxidative eliminations [51], Moreover, well-defined molybdenum, rhodium, and iridium phosphine complexes have been prepared on copolymers of PEG and silica [52]. Several reviews have covered the preparation and application of support-bound reagents, including transition metal complexes [53-59]. Examples of the preparation and uses of organomercury and organo-zinc compounds are discussed in Section 4.1. 

Similar to the tin- and zinc-based methodologies, electron deficient alkenes were found to strongly catalyze the reductive elimination step.155 156-395 Organomercury reagents are also believed to add via metal addition.385... 

The first part of this section considers those studies related to zinc metalloenzymes and to the interaction of the metals with other proteins and nucleic acids the second part considers the uses of organomercurials. The same format as last year has been followed, except for the exclusion of the section considering the environmental effects of the metals and organomercurials. 

Like the dialkylmagnesiums, the dialkylzincs can also be formed by the action of metallic zinc on the corresponding organomercury compounds ... 

In this section, we will discuss organometallics in which the metal is cadmium, mercury, or zinc. Grignard reagents and organolithium compounds can be converted to heavy-metal derivatives by reaction with salts of these metals. The reaction is driven forward by the tendency for formation of the ionic salt of the more electropositive metal. This reaction is well documented for organocadmium compounds and organomercurials ... 

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