Abstract
Abstract (7R,14R)-(+)-7,14-Dihydro-7,14-ethanodibenz[a,h]anthracene (1), and the 2,9-dimethyl- (2) and 2,4,9,11-tetramethyl- (3) derivatives were synthesized from (9R,10R)-(+)-9,10-dihydro-9,10-ethanoanthracene-1,5-dicarbaldehyde (4) of known absolute configuration. The CD spectra of 1, 2, and 3 clearly exhibit positive first and negative second Cotton effects due to the coupling of the 1Bb transitions of two naphthalene chromophores: Δε237.0=+326.5, Δε224.0=−180.5, A=+507.0, for 1; Δε240.6=+371.5, Δε227.0=−149.4, A=+520.9, for 2; Δε242.0=+340.3, Δε225.0=−88.0, A=+428.3, for 3. Since the sign of the A values is positive, positive exciton chirality between the two long axes of the naphthalene moieties is assigned. The (7R,14R) absolute configuration of 1, 2, and 3 is established by both CD exciton chirality and X-ray Bijvoet methods.
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