Evidence for two binding sites of lanthanoid shift reagents at the carbonyl groups of camphor and canthaxanthin
- 1 January 1977
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 11,p. 1390-1400
- https://doi.org/10.1039/p29770001390
Abstract
By observing the shifts and broadening of 1H and 13C n.m.r. signals of camphor induced by lanthanoid shift reagents, it has been shown that the metal binds at two sites on the carbonyl group. A similar situation has been demonstrated for the binding of shift reagents to the carbonyl groups in the ionone rings of the carotenoid canthaxanthin. With the aid of a novel computer program (LISCA), employing a least-squares fitting routine, the conformations of the carotenoid have been investigated. The ring-flip forms are equally populated in solution at room temperature. Our results point to, but cannot distinguish between, either an ionone ring–polyene side chain angle of ca. 90° or a 50 : 50 equilibrium mixture of the forms s-trans and 40° away from s-cis.Keywords
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