August Rüttimann

The substrate specificity of tocopherol cyclase

The substrate specificity of the enzyme tocopherol cyclase from the blue-green algae Anabaena variabilis (Cyanobacteria) was investigated with 11 substrate analogues revealing the significance of three major recognition sites: (i) the OH group at C(1) of the hydroquinone, (ii) the (E) configuration of the double bond, and (iii) the length of the lipophilic side chain. Experiments with two affinity matrices suggest that substrates approach the enzymes active site with the hydrophobic tail.

Some recent advances in the synthesis of natural carotenoids

Abstract The total syntheses of naturally occurring (3R,3′R)-zeaxanthin, (3S,3′S)-astaxanthin, (3S,3′S)-asterinic acid and of some related xanthophylls are discussed. Asymmetric hydroboration has been applied to the total synthesis of all configurational isomers of zeaxanthin. The total synthesis of natural actinioerythrin is described and the absolute configuration confirmed by X-ray crystallographic analysis of an intermediate. The optical resolution of α-hydroxy-carbonyl compounds via (−)-camphanic acid esters appears to be generally applicable and can be used as an analytical method for the determination of the optical purity of α-hydroxy-carbonyl carotenoids. Some technological applications are indicated.