ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
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: (5R,8R,5′R,8′R)-aurochrome (2) and its racemate, Meso-(5R,8R,5′S,8′S)-aurochrome (3), (5 R,8 S,5′ R,8′ S)-aurochrome (4) and its racemate, meso-(5R,8S,5′S,8′R)-aurochrome (5), (5R,8R,5′R,8′S)-aurochrome (6) and its racemate. The (5RS,8RS,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 CHCl3, in the presence of HCl, undergo epimerization at C(8). Those epimers with CH3 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 (5RS, 8RS)- and (5RS, 8SR)-12′-apo-aurochrome-12′-als (21 and 22, respectively).
Zusätzliches Material:
12 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19840670218
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