Synthesen von enantiomerenreinen Apoviolaxanthin‐säuren, ‐olen und ‐alen (Persicaxanthin, Sinensiaxanthin und β‐Citraurin‐epoxid) und ihrer furanoiden Umlagerungsprodukte

Synthesis of Enantiomerically Pure Apoviolaxanthinoic Acids, Apoviolaxanthinols, and Apoviolaxanthinals (Including Persicaxanthin, Sinensiaxanthin, and β‐Citraurin Epoxide) and of their Furanoid Rearrangement Products Starting from (1′ S ,2′ R ,4′ S ,2 E ,4 E )‐5‐(1′,2′‐epoxy‐4′‐hydroxy‐2′,6′,6′‐trimethylcyclohexy1)‐3‐methy1‐2,4‐pentadienal ( 3 ), a recently described synthon [6], a full range of C 20 ‐, C 25 ‐, C 27 ‐, and C 30 ‐polyenic acids, alcohols, and aldehydes and their (8 R )‐ and (8 S )‐diastereoisomeric furanoid rearrangement products was prepared. The synthetic C 25 ‐alcohols proved to be identical with persicaxanthin (= 12′‐apoviolaxanthin‐12′‐ol) and perisicachromes (= 12′‐apoauroxanthin‐12′‐ols) and the C 27 ‐alcohols analogously with sinensiaxanthin and sinensiachromes. A correlation between the sign of the Cotton effects in the CD spectra of 5,6‐and 5,8‐epoxides and their configuration at C(6) and C(8), respectively, was established.