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Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus Oxo-isophoron. I. Modifizierung der Kienzle-Mayer-Synthese von (3S 3′S)-Astaxanthin

✍ Scribed by Erich Widmer; Reinhard Zell; Teodor Lukáč; Marco Casadei; Peter Schönholzer; Emil A. Broger

Publisher
John Wiley and Sons
Year
1981
Tongue
German
Weight
798 KB
Volume
64
Category
Article
ISSN
0018-019X

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✦ Synopsis

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. I. Modification of the Kienzle‐Mayer‐Synthesis of (3__S__, 3′S)‐Astaxanthin

An efficient synthesis of (3__S__, 3′S)‐astaxanthin (1a) in high yield and optical purity starting from (4__R__, 6__R__)‐4‐hydroxy‐2,2,6‐trimethylcyclohexanone (4) is reported. The absolute configuration of 1a, previously derived from ORD. data, has been confirmed by X‐ray analysis of 5, a derivative of 6‐oxo‐isophorone (2). The key features of the improved synthesis are the two‐step conversion of 4 to the key intermediate (4__S__)‐2,6,6‐trimethyl‐4‐hydroxy‐2‐cyclohexen‐1‐one (14), a new method for the partial reduction of the sterically hindered triple bond of (S)‐6‐hydroxy‐3‐(5‐hydroxy‐3‐methyl‐3‐penten‐1‐ynyl)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐one (32), and Wittig olefination of the dialdehyde 1,6‐dimethyl‐1,3,5‐octatrienedial (38) using phosphonium salt 37 with a free hydroxyl group.

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