Exchange strategies

Wanzlick was the first to use an acetate salt in the synthesis of a mercury bis-NHC complex starting from mercury(ll) diacetate [Eq. (8)]." There are other examples using the very same strategy. Exchanging the anionic parts of the mercury precursor and the imidazolium salt, i.e., using HgCh and imidazolium acetate, works as well. ... 

L. iitortunately, this simple approach does not work well, but Becke has proposed a strategy which does seem to have much promise [Becke 1993a, b]. In his approach the exchange-correlation energy Exc is written in the following form ... 

Eda and Kurth applied a similar solid-phase combinatorial strategy for synthesis of pyridinium, tetrahydropyridine, and piperidine frameworks as potential inhibitors of vesicular acetylcholine transporter. One member of the small library produced was prepared from amino-functionalized trityl resin reacting with a 4-phenyl Zincke salt to give resin-bound product 62 (Scheme 8.4.21). After ion exchange and cleavage from the resin, pyridinium 63 was isolated. Alternatively, borohydride reduction of 62 led to the 1,2,3,6-tetrahydropyridine 64, which could be hydrogenated to the corresponding piperidine 65. 

Natural mutation of amino acids in the core of a protein can stabilize the same fold with different complementary amino acid types, but they can also cause a different fold of that particular portion. If the sequence identity is lower than 30% it is much more difficult to identify a homologous structure. Other strategies like secondary structure predictions combined with knowledge-based rules about reciprocal exchange of residues are necessary. If there is a reliable assumption for common fold then it is possible to identify intra- and intermolecular interacting residues by search for correlated complementary mutations of residues by correlated mutation analysis, CMA (see e.g., http //www.fmp-berlin.de/SSFA). 

---