Groups, equatorial modified

A modified Huang-Minlon reduction was found advantageous in the conversion of methyl eholate to lithocholic acid without purification of intermediates. The 3-hydroxyl group (equatorial) is selectively succinoylated, the hydroxyl functions... 

The steric parameters for the estimation of reactant state effects were chosen to be the conformational free energy differences for cyclohexane axial-equatorial equilibria (A-values) (8). In order to establish the methyl group as the standard size group, modified A-values (A ) for the various groups were used, by simply subtracting the A value for the methyl group (1.70) from the A values of the various substituents ... 

This section deals with reactions which involve only the organo-ligand, whether unmodified or modified by the loss or gain of a proton, and the cobalt. After considering established and possible mechanisms (Section B,l) we list examples to show how reactivity is influenced by different functional groups and substituents (Section B,2), and by changes in the axial and equatorial ligands (Section B,3). 

Figure 13 7 The two-metal-ion mechanism for polynucleotide polymerases. One metal ion (usually Mg2+) activates the 3 -OH group of the primer terminus and stabilizes one of the partly negatively charged equatorial oxygen atoms of the phosphoryl group, whereas the other binds the phosphoryl oxygen and the oxygen atoms of the pyrophosphate leaving group. The two metal ions are 3.9 A apart. This mechanism fits both RNA and DNA polymerases. [Modified from T. A. Steitz, Nature, Lond. 391,231 (1998).]...

Bile acids can be modified to many derivatives due to their unique molecular structures, as listed in Table 1. First, we can convert the functional groups at the side-chains from carboxylic acid to amide, alcohol, ester, and so on. Second, we can change the length of the side-chains by decreasing or increasing their methylene number. Third, we can regulate the direction of the hydroxyl groups of the skeletons at the axial or equatorial positions. 

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