173197-31-4Relevant academic research and scientific papers
Hindered rotation in arylnaphthalene lignans
Charlton, James L.,Oleschuk, Curtis J.,Chee, Gaik-Lean
, p. 3452 - 3457 (2007/10/03)
Many arylnaphthalene lignans show biological activity and although few of them contain stereogenic centers, they may nevertheless be chiral if there is hindered rotation about the aryl-naphthalene bond. A relatively high barrier to rotation may give rise to separable rotational enantiomers (atropisomers) which might have quite different pharmacological properties. In order to investigate this possibility we have synthesized the natural products justicidin A, justicidin B, retro-helioxanthin, retro-justicidin B, and helioxanthin as well as four other arylnaphthalenes lignan analogs. We have studied the aryl-naphthalene rotational barrier in these compounds by dynamic NMR and HPLC and find barriers to rotation ranging from 16.9 to 21.5 kcal/mol. This translates to half-lives for individual atropisomers of less than 10 min at room temperature. The experimentally found barriers are compared to those obtained from molecular orbital calculations.
Synthesis of acetylenedicarboxylic acid esters and asymmetric Diels-Alder reactions of the bis(methyl (S)-lactyl) ester
Charlton, James L.,Chee, Gaiklean,McColeman, Heather
, p. 1454 - 1462 (2007/10/03)
A general method has been developed for the preparation of acetylenedicarboxylic acid esters and applied to the synthesis of both achiral and chiral esters.Diels-Alder reactions of one of the chiral esters, the bis(methyl (S)-lactyl) ester, with various types of dienes, such as phenylbutadiene, orthoquinodimethanes, and isobenzofuran, have been investigated.Moderate asymmetric induction was observed in reactions with dienes bearing an α-hydroxyl group.In one case, an unusual solvent-induced reversal of asymmetric induction was observed.Key words: acetylenedicarboxylic acid esters, phenylbutadiene, orthoquinodimethanes, isobenzofurans, Diels-Alder , asymmetric.
