ASYMMETRIC HYDROGENATION OF AMINO-ACID PRECURSORS PROMOTED BY A NEW-TYPE OF CHOLESTEROL AMPHIPHILES - INVESTIGATION OF AGGREGATION BEHAVIORAND STEREOSELECTIVE EFFECTS

Reaction of 2-hydroxyethanesulfonic acid sodium salt, 3-hydroxypropane sulfonic acid sodium salt or 2-aminoethanesulfonic acid sodium salt wi th cholest-5-en-3 beta-ol-3-chloroformate yields the chiral amphiphili c compounds 2-(cholest-5-en-3 beta)oxy-carbonyloxy-ethanesulfonic acid sodium salt 1, 2-(cholest-5-en-3 beta)oxy-carbonyloxy-propanesulfonic acid sodium salt 2 and 2-(cholest-5-en-3 beta)oxy-carbonylaminoethane sulfonic acid sodium salt 3, respectively. Another chiral amphiphile 2 -(cholest-5-en-3 beta)oxy-carbonylethanesulfonic acid sodium salt 4 wa s synthesized by treating cholest-5-en-3 beta-ol with sulfopropionic a cid anhydride. The surfactants form vesicles in aqueous solutions, as shown by electron microscopy. Stepwise destruction of these vesicles b y addition of ethanol or methanol was proved by Circular Dichroism (CD ) measurements. Especially compound 3 shows pronounced induced CD effe cts with the achiral dye 3,6-diamino-acridine-sulfate (proflavine). Th e synthesized chiral amphiphiles were used in the asymmetric hydrogena tion reaction of methyl (Z)-alpha-acetamidocinnamate. In the case of a n achiral rhodium complex as catalyst the prepared surfactants 1, 2, a nd 4 are able to provide an enantiomer excess by themselves. The best ee-value reached was 8.5% methyl (R)-N-acetylphenyl-alaninate in conne ction with compound 4.