Enantioselective reactions, definition compounds

The [3-hydroxy amines are a class of compounds falling within the generic definition of Eq. 6A.6. When the alcohol is secondary, the possibility for kinetic resolution exists if the Ti-tartrate complex is capable of catalyzing the enantioselective oxidation of the amine to an amine oxide (or other oxidation product). The use of the standard asymmetric epoxidation complex (i.e., T2(tartrate)2) to achieve such an enantioselective oxidation was unsuccessful. However, modification of the complex so that the stoichiometry lies between Ti2 (tartrate) j and Ti2(tartrate)1 5 leads to very successful kinetic resolutions of [3-hydroxyamines. A representative example is shown in Eq. 6A.11 [141b,c]. The oxidation and kinetic resolution of more than 20 secondary [3-hydroxyamines [141,145a] provides an indication of the scope of the reaction and of some... 

We then achieved the enantioselective synthesis of (IS, 3S,lR)-96 as shown in Figure 4.47,82 Evans chiral auxiliary was attached to acid A, giving B. Methylation of B and subsequent hydrolysis of the product afforded C. Acid C was converted to D. Then, intramolecular Diels-Alder reaction of D furnished E. Methylenation of E with Tebbe reagent yielded the desired (15 ,35, 7/ )-96.82 It was shown definitely that only ( S,3S,lR)-96 is bioactive, while other isomers are inactive.83 It must be added that a-himachalene obtained from Himalayan deodar Cedrus deodara possesses the opposite 1 R,1S configuration. Insects and plants sometimes produce similar compounds with different absolute configuration. 

Despite the great synthetic utihty of diazocarbonyl compounds in the generation of carbonyl ylide intermediates, definitive mechanistic studies on the metal-catalyzed cycloaddition of carbonyl yhdes are scarce. Among the various metal catalysts, dirhodium(II) catalysts are the most effective and versatile for diazo decomposition. Because of the rapid catalytic tmnovers of these reactions, structural information about the intermediates is difficult to obtain. A reasonable mechanism can be rationahzed on the basis of product distribution, and especially on the basis of enantioselective outcome of various carbonyl yhde reactions [55-63]. 

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