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Syntheses of the trans,meso- and racemic C11 acids, degradation products of diterpene acids

Banerjee, DK and Balasubrahmanyam, SN (1966) Syntheses of the trans,meso- and racemic C11 acids, degradation products of diterpene acids. In: Journal of the Chemical Society C Organic . pp. 1458-1467.

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Abstract

Syntheses of the isomers of the C11 acid, 1(a),3(a)- dimethylcyclohexane-1 (e),2(e),3(e)-tricarboxylic acid (A) and 1(a),3(e)-dimethylcyclohexane-1(e),2(e),3(a)-tricarboxylic acid (B), the latter by two different routes, are reported. Two of the four possible isomers of the precursor triester, trimethyl 1-methylcyclohexane-1,2,3-tricarboxylate, on individual methylation followed by hydrolysis, gave the trans,meso-acid (A), identified by comparison with an authentic sample, and the cis,trans-form (B) whose structure and configuration were proved by comparison with a specimen obtained by the unambiguous and highly stereoselective second synthesis. This demonstrated that methylation of the triester isomers occurs stereospecifically and exclusively at C-3. In the second sequence, it has been possible to assign definite conformations to four key intermediates and the final product, directly from n.m.r. spectra, from changes in these spectra accompanying specific steps, and from chemical evidence. Comparison of the n.m.r. spectra of the isomeric triesters (A) and (B) has provided unequivocal proof of the accepted trans,meso configuration for the abietic acid degradation product (A).

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 17 May 2010 08:56
Last Modified: 19 Sep 2010 06:06
URI: http://eprints.iisc.ernet.in/id/eprint/27870

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