Short, Enantioselective Total Synthesis of Stephacidin A, Angew.
A Short, Enantioselective Total Synthesis of Okaramine N, J.
Highly enantioselective asymmetric syntheses, , enantioselective addition of alkylmetal reagents to aldehydes and imines, enantioselective conjugate addition of dialkylzincs to enones, and asymmetric autocatalysis have been developed by designing asymmetric catalysts (or chiral ligands) and chiral environment of the reactions. Automultiplication of chiral compounds by asymmetric autocatalysis was discovered where a chiral product acts as a chiral catalyst for its own production. Asymmetric autocatalysis with>99.5% ee in a yield of > 99% was attained using pyrimidyl alkanol as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. The asymmetric autocatalysis exhibits significant positive non-linear effect on ee. Asymmetric autocatalyst with very low (. 0.00005%) ee enhances its ee significantly up to > 99.5% ee during the consecutive asymmetric autocatalysis without the assistance of any other chiral auxiliary. Moreover, amino acids and  helicene with very low ee which are produced by asymmetric photolysis and photosynthesis using circularly polarized light serve as chiral initiators of asymmetric autocatalysis, and pyrimidyl alkanol with high ee is obtained. Inorganic chiral crystals such as quartz and sodium chlorate, [2.2] paracyclophanes, allenes, chiral cobalt complexes due to the topology of coordination, chiral primary alcohols due to the deuterium substitution also work as chiral initiators. Asymmetric autocatalysis is capable to discriminate efficiently the chirality of various chiral compounds. Moreover, the reactions of pyrimidinecarbaldehyde with diisopropylzinc without adding chiral substance exhibit the formation of enantioenriched S or pyrimidyl alkanols with approximate stochastic distribution, which indicates the reaction is a spontaneous absolute asymmetric synthesis. These results correlate for the first time the proposed origins of chirality of organic compounds with the chirality of organic compounds with very high ee.
Highly Enantioselective Synthesis of Indolines: …
In their report on the stoichiometric DTR of rac-2, Coldham, et al, indicated that the resolution is facilitated by the addition of lithium isopropoxide. With this in mind, we investigated the enantioselectivity of dilithio diaminoalkoxides 7–9 in a stoichiometric DTR using the Coldham conditions. We were gratified to find the high er’s shown in . Note that diastereomeric ligands 8 and 9 afford very high er, and opposite configurations of 3.
Yoo, K.; Kim, H.; Yun, J.* "Enantioselective Synthesis of (R) ..
Our studies following the approach outlined above have led us to the discovery of powerful and practical chiral organic catalysts promoting highly enantioselective reactions by general base catalysis. We also established that the general base catalysis could be coupled with electrophile-activating catalysis such general acid catalysis and iminium catalysis to form powerful bifunctional catalysis for asymmetric reaction development. These concepts have been successfully applied to the development of a wide range of novel and highly efficient asymmetric reactions of general scopes. Many of these reactions have already found wide applications in target- and diversity-oriented synthesis. Our reactions have also been developed into viable tools for industrial manufacturing of chiral compounds.