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Die diasteromeren Aurochrome: Synthese, Analytik und Chiroptische Eigenschaften
Author(s) -
Acemoglu Murat,
Eugster Conrad Hans
Publication year - 1984
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.19840670218
Subject(s) - chemistry , diastereomer , epimer , enantiomer , isomerization , stereochemistry , optically active , deprotonation , phosphonate , organic chemistry , catalysis , ion
The Diastereomeric Aurochromes: Their Synthesis, Analysis and Chiroptical Properties (all‐ E )‐Aurochrome (5,8:5′,8′‐diepoxy‐5,8,5′,8′‐tetrahydro‐β,β‐carotene; 1 ) has two pairs of constitutionally identical chiral centres and, therefore, is expected to exist in four pairs of enantiomers and two meso ‐forms. Using starting materials with well‐defined configuration, we performed the syntheses of the following pure aurochromes: (5 R ,8 R ,5′ R ,8′ R )‐aurochrome ( 2 ) and its racemate, Meso ‐(5 R ,8 R ,5′ S ,8′ S )‐aurochrome ( 3 ), (5 R ,8 S ,5′ R ,8′ S )‐aurochrome ( 4 ) and its racemate, meso ‐(5 R ,8 S ,5′ S ,8′ R )‐aurochrome ( 5 ), (5 R ,8 R ,5′ R ,8′ S )‐aurochrome ( 6 ) and its racemate. The (5 RS ,8 RS ,5′ SR ,8′ RS )‐aurochrome ( 7 ) was detected chromatographically, using a HPLC system that allows clean separation of the four racemic‐ (or optically active) and the two meso ‐aurochromes. The optically active autochromes 2 and 4 exhibit non‐conservative CD spectra with strong Cotton effects of opposite but not mirror‐like tracings. Solutions of aurochromes in CHCl 3 , in the presence of HCl, undergo epimerization at C(8). Those epimers with CH 3 trans to C(9) slightly predominate under equilibrium conditions. Deprotonation of the phosphonate (±)‐ 14 with strong base causes isomerization at the terminal oxirane into a dihydrofuran. This reaction allowed convenient syntheses of the diastereoisomeric aurochromes (±)‐ 2, 3 , (±)‐ 4, 5 , (±)‐ 6 , and (±)‐ 7 and of (5 RS , 8 RS )‐ and (5 RS , 8 SR )‐12′‐apo‐aurochrome‐12′‐als ( 21 and 22 , respectively).