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Synthese von optisch aktiven, natürlichen Carotioiden und strukturell verwandten Naturprodukten. X. Synthese von (3 R ,3′ S , 5′ R )‐Capsanthin, (3 S ,5 R ,3′ S ,5′ R )‐Capsorubin, (3′ S ,5′ R )‐Kryptocapsin und einigen verwandten Verbindungen. Ein neuer Zugang zu optisch aktiven Fünfring‐Carotinoidbausteinen durch Hydroborierung
Author(s) -
Rüttimann August,
Englert Gerhard,
Mayer Hans,
Moss Gerard P.,
Weedon Basil C. L.
Publication year - 1983
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.19830660706
Subject(s) - chemistry , optically active , yield (engineering) , stereochemistry , aldol condensation , ketone , aldol reaction , toluene , organic chemistry , catalysis , materials science , metallurgy
Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. X. Synthesis of (3 R ,3′ S ,5′ R )‐Capsanthin, (3 S ,5 R ,3′ S ,5′ R )‐Capsorubin, (3′ S ,5′ R )‐Cryptocapsin, and Some Related Compounds. A New Approach to Optically Active, Five‐Membered‐Ring Carotenoid Building Units by Hydroboraton The synthesis of (3 R ,3′ S ,5′ R )‐capsanthin (1) , (3 S ,5 R ,3′ S ,5′ R )‐capsorubin (2) , and (3′ S ,5′ R )‐cryptocapsin (3) , found in the red paprika Capsicum annuum , is described using (+)‐camphor (7) as a readily available starting material. As the key reaction, the unsaturated acetal 16 is hydroborated with (+)‐diisopinocampheylborane to give the hydroxy ketone 12a in very high chemical and optical yield. A subsequent aldol condensation with 13 in THF/toluene gives 2 in high yield. The C 40 ‐compounds 1 and 3 are synthesized using the same type of condensation. The pigments 1–3 are transformed by an Oppenauer oxidation to (3 R ,5′ R )‐capsanthone (5) , (5 R ,5′ R )‐capsorubone (4) and (5′ R )‐cryptocapsone (6) , respectively.