Királis koronaéterekkel katalizált enantioszelektív szintézisek és ''deracemizációs'' reakciók vizsgálata = Investigation of enantioselective synthesis and deracemization reactions by chiral crownethers

A monoszacharidokbol felepulő kiralis koronaeterek aszimmetrikus indukciot kepesek kifejteni bizonyos reakciokban, ha kiralis fazistranszfer katalizatorkent alkalmazzuk azokat. Uj kiralis metil-α-D-glukopiranozid- es α-D-mannopiranozid-alapu monoaza-15-korona-5 tipusu etereket szintetizaltunk, melyek korona-gyűrűjeben oxigen, ken vagy nitrogen atomok voltak, valamint foszfor atomot tartalmazo 17-korona-7 tipusu vegyuleteket. Vizsgaltuk a makrociklusok alkali fem kationokkal mutatott komplexkepző kepesseget. Nehany koronaeter katalizatorkent jelentős aszimmetrikus indukciot eredmenyezett: a 2-nitropropan kalkonra es kalkon analgonokra tortenő Michael addiciojaban (80-94 % ee), kalkonok terc-butil-hidroperoxiddal tortenő epoxidacios reakciojaban (75-94 % ee) es α-klor-acetofenon szubsztitualt benzaldehidekkel lejatszodo Darzens kondenzaciojaban (60-72 % ee) ketfazisu reakciokban. A katalizatort felepitő szenhidrat kiralis tulajdonsaga jelentősen befolyasolja a kemiai termelest es az enantioszelektivitast. Peldaul, amig a D-glukopiranozidbol felepulő koronaeterek a 2R,3S konfiguracioju epoxiketon keletkezeset preferaltak (max. 94 % ee), addig a D-mannopiranozid-alapu katalizatorok az ellentetes, 2S,3R konfiguracioju termek keletkezeset segitettek elő (max. 82 % ee) a kalkon epoxidacios reakciojaban. Az uj epoxi-ketonok abszolut konfiguraciojat CD spektroszkopiasan hataroztuk meg. A reakciok mechanizmusat molekulamodel szamitasokkal bizonyitottuk. | The chiral crown ethers incorporating monosaccharide moiety in their ring, are able to general asymmetric induction as chiral phase transfer catalysts in certain reactions. New chiral methyl-α-D-glucopyranoside- and methyl-α-D-mannopyranoside-based monoaza-15-crown-5 ethers having oxygen, sulphur or nitrogen atoms in the crown ring, and 17-crown-7 type ethers containing a phosphorus atom have been synthesized. The complex forming ability of the compounds with alkali metal and ammonium cations was investigated. Some crown ethers resulted in significant asymmetric induction as catalysts in Michael addition of 2-nitropropane to substituted chalcones and heteroaromatic chalcone analogues (80-94 % ee), in the epoxidation of the different chalcones with tert-butylhydroperoxide (75-94 % ee) and in the Darzens condensation of phenacyl chloride with substituted benzaldehydes (60-72 % ee). The chiral nature of the carbohydrate in the catalyst, the quality of the side arm attached to the nitrogen atom had a significant effect on the enantioselectivity. For example the use of D-glucopyranoside-based crown ethers promoted the formation of epoxyketone with 2R,3S configuration (94 % ee), at the same time, the D-mannopyranoside-based catalyst preferred the formation of 2S,3R enantiomer (82 % ee) in the epoxidation of chalcone. The absolute configurations of epoxyketones were determined by CD spectroscopy. The mechanism of the reactions was evaluated by molecule modeling calculations.