Synthese von Astaxanthin aus β‐Jonon. I. Erschliessung der enantiomeren C₁₅‐<i>Wittig</i>salze durch chemische und mikrobiologische Racematspaltung von (±)‐3‐Acetoxy‐4‐oxo‐β‐jonon

Abstract

Synthesis of Astaxanthin from β‐Ionone. I. A Route to the Enantiomeric C 15 ‐ Wittig Salts by Chemical and Microbial Resolution of (±)‐3‐Acetoxy‐4‐oxo‐β‐ionone Racemic 3‐acetoxy‐4‐oxo‐β‐ionone ( 10 ) was synthesized from the industrially accessible intermediate β‐ionone ( 5 ). Resolution of 10 into its enantiomers was achieved via the corresponding diastereomeric camphanates and by microbial resolution. Site‐selective alkylation of racemic and of optically pure 3‐acyloxy‐4‐oxo‐β‐ionones with vinyl magnesium chloride at −70° furnished the corresponding 3‐acyloxy‐4‐oxo‐9‐vinyl‐β‐ionols which could be transformed to the Wittig salts 1, 3 and 4 , respectively, following known procedures [1].