Enantiomer recognition reactivity

Reactivity. Enantiomer recognition in solution results in various intriguing stereochemical outcomes for organic reactions. The molecular interaction may be direct or may occur by way of some other atoms or molecules. 

Rate-determining step, hydroformylation, 163 Reactivity, enantiomers, 286 Recognition, enantiomers, 278 Reduction and oxidation, 5 Reductive coupling, dissolving metal, 288 Reductive elimination, 5, 111 Resolution. See Kinetic resolution Rhenium-carbene complexes, 288 Rhodium-catalyzed hydrogenation, 17, 352 amino acid synthesis, 18, 352 BINAP, 20... 

Aminolyses of rac-14a were tried with several types of amines, i.e., oc-amino acid derivatives, ) -amino alcohols, and 3-amino-) -lactams (Scheme 4). The results are as follows. In the case of a-amino acid derivatives, the (S)-enantiomer reacted with (4/ )-HDMCTT (14a) preferentially and vice versa [(/ )-enantiomer + (4S)-HDMCTT], which was in good agreement with the chiral recognition of racemic amine with (4/ )-AMCTT (14). In the case of ) -amino alcohol derivatives, the (S)-enantiomer showed a preferential reactivity to (4S)-HDMCTT, resulting in the recovery of (4/ )-HDMCTT. In the case of 3-amino-) -lactams, (R)-penam-, (R)-cephem-, and (S)-oxacephem derivatives all showed a preferential reactivity to (4S)-HDMCTT (R)-oxacephem derivatives reacted predominantly with (4/ )-HDMCTT. 

Proteins naturally recognize enantiomers. The study of protein recognition of enantiomers was applied to analyze the reactivity of DAO, which selectively oxidizes (R)-amino acids [(R)-AAs]. DAO was the second flavoenzyme to... 

Kinetic resolutions of allylic esters have also been conducted. As noted in Chapter 14, in most cases, catalysts that are selective for kinetic resolution of substrates containing one type of functional group are also selective for reactions of meso substrates and vice versa.The enantioselective reaction of one acetate of a meso substrate involves similar stereochemical recognition to reaction of two enantiomers of a racemic mixture of allylic esters. In one illustrative example, an allylic acetate underwent reaction with a pivalate nucleophile to form the allylic pivalate product, which is less reactive than the starting compound (Equation 20.54). Reaction of one enantiomer of the racemic allylic acetate occurs preferentially, and the pivalate product is formed enantioselec-tively. The product of the resolution in Equation 20.54 was carried forward to form (+)-cyclophellitol. 

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