ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
(+)-cis-Khellactone methyl ether (4) and (-)-trans-khellactone methyl ether (6) had earlier been assigned the absolute configurations 3′-S; 4′-S and 3′-S; 4′-R, respectively, on the basis of the FREUDENBERG, rule. Both compounds together with their defunctionalised derivatives (-)-7 and (+)-8 (=(+)-lomatin), obtained from a mixture of (+)-visnadin (1) and (+)-samidin (2), were investigated by the HOREAU method. A conformational analytical study showed that the optical yield should rise in the order 4 〈 6 〈 7, 8. This order was found and the α-phenylbutyric acid liberated was always dextrorotatory. The centre 3′ of the khellactones and their derivatives must be R-chiral and not S. Treatment of (-)-6 with pyridinium perbromide gave (-)-trans-3-bromokhellactone methyl ether (11) as orthorhombic crystals. The X-ray crystal structure determination was made using the anomalous scattering of the Mo-K α radiation by Br. The result, - centre 3′ R-chiral (fig. g) - showed that the HOREAU method was correct.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19690520503
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