Chiral compounds nonaromatic

Although about 20 polysaccharide-based CSPs have been commercialized and much work on enantioresolution has been carried out on these phases, it remains very difficult to predict the best CSP for the chiral resolution of a particular compound. It has been observed that most of the resolved racemic compounds contain aromatic rings or groups such as carbonyl, sulfinyl, nitro, amino, and benzoyl. However, some reports have been published on the chiral resolution of nonaromatic racemates on polysaccharide CSPs [61]. As in the case of other CSPs, polysaccharide-based CSPs do not require a certain combination of functional groups. However, only one group can afford a satisfactory separation. Presumably some chiral space (e.g., a concavity or ravine existing on a polysaccharide derivative) could enable such a separation [62],... 

In 1994, the first enantioselective trifluoromethylation reaction was achieved with the Ruppert-Prakash reagent, TMSCF3, in the presence of the cinchona-based quaternary ammonium fluoride 140 [65]. The chiral induction can arise from the dual activation mode of the catalyst, that is, the fluoride anion acts as the nucleophilic activator of (TMS)CF3 and the chiral ammonium cation activates the carbonyl group of 141. However, the observed ee values of the obtained carbinols 142 do not exceed 51 % and decrease considerably when nonaromatic carbonyl compounds (15% ee for R1 = n-C7H15 R2 = H) are used, which implies that 7t-7t stacking interactions between the carbonyl compound and cinchoninium occur (Scheme 8.54). 

The application of bacterial strains containing these dioxygenases has used for transformation of environmental pollutant aromatic compounds to nonaromatic compounds (Cavalca et al. 2004 Parales and Haddock 2004). Moreover, the c/5-diols produced by dioxygenases are attractive because of their inimitable chiral structures and their potentials in industrial synthesis for useful chemical products... 

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