Site-selective reagents

Indirect evidence for the existence of different conformations of H,K-ATPase has been gained by site-selective reagents. Eor example, Schrijen et al. [67,95] demonstrated that Mg increased exposure of an essential arginine residue near the ATP-binding site and Mg " caused an increase in the number of reactive sulfhydryl groups on the enzyme. 

Ethoxy)-allylidenecyclopropane (136a) readily underwent Diels-Alder reaction with activated dienophiles under mild conditions (Table 14) [33]. Only one regioisomer was formed with unsymmetrically substituted dienophiles such as methyl maleic anhydride (137), and quinones 138-141 (entries 2 and 3-6). AH the cycloadducts 143-147 derive from an endo approach between the two reagents. Two site-isomers were obtained in 96 4 ratio with 3-isopropyl-6-methyl-p-quinone (141) (entry 6) and the high site-selectivity observed in this... 

G.S. Lai, Site-selective fluorination of organic compounds using 1-alkyl-4-fluoro-1, 4-diazabicyclo[2.2.2]octane salts (selectfluor reagents), J. Org. Chem. 58 (1993) 2791-2796. 

Efforts to find optimally reactive, less toxic, less toxic, nonexplosive, more stable and cost-effective chemical reagents capable of the transfer of a fluorine atom site-selectively into a comprehensive range of organic molecules promises to be rewarded with the promotion of 1-fluoro-substituted l,4-diazoniabicyclo[2.2.2]octane salts as versatile fluorinating reagents. 

Many reagents known for the direct conversion of alcohols into halides have been used to achieve site-selective nucleophilic substitution in polyhydroxy compounds [44-46,62]. In some cases, it is possible to effect selective displacements of primary alcohols in the presence of secondary ones, and to achieve differential substitutions of secondary alcohols in unprotected sugars [44,45,64,65] (Scheme 4). 

Maggi, R. Schlosser, M. Optional site selectivity in the metalation of o- and p-anisidine through matching of reagents with neighboring groups. /. Org. Chem. 1996, 61, 5430- 442 5434. 

Figure 1. Structural complementarity between reagent and target site usually is required for site selection reaction.

Active Site Selective Reagents - Naturally Occurring Toxins and Laboratory Tools... 

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