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Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. III. Ein neues Konzept für die Synthese der enantiomeren Astaxanthine
Author(s) -
Zell Reinhard,
Widmer Erich,
Lukáč Teodor,
Leuenberger Hans Georg Wilhelm,
Schönholzer Peter,
Broger Emil A.
Publication year - 1981
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19810640752
Subject(s) - chemistry , enantiomer , enantiomeric excess , stereochemistry , isophorone , total synthesis , absolute configuration , enantioselective synthesis , organic chemistry , catalysis
Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. III. A New Concept for the Synthesis of the Enantiomeric Astaxanthins A new and efficient concept for the total synthesis of (3 S , 3' S )‐ and (3 R , 3' R )‐astaxanthin ( 1a and 1c , resp.) in high overall yield and up to 99,2% enantiomeric purity is described. Key intermediates are the ( S )‐ and ( R )‐acetals 10 and 17 , respectively (Scheme 2) . These chiral building blocks were synthesized via three different routes: a) functionalization of the enantiomeric 3‐hydroxy‐6‐oxo‐isophorons 4 ) 2 and 11 , respectively (Scheme 2) ; b) optical resolution of 3,4‐dihydroxy‐compound 4 ) 19 (Scheme 3) , and c) fermentative reductions of 6‐oxo‐isophorone derivatives (Schemes 4 and 5) . ‐ The absolute configurations of the two intermediates 12 and 13 (Scheme 2) have been confirmed by X‐ray analysis. ‐ The final steps leading to the enantiomeric astaxanthins are identical with those described for optically inactive astaxanthin [1].