A simple route to enantiopure bis-lactones: synthesis of both enantiomers of epi-nor-canadensolide, nor-canadensolide, and canadensolide

Mondal, Sujit ; Ghosh, Subrata (2008) A simple route to enantiopure bis-lactones: synthesis of both enantiomers of epi-nor-canadensolide, nor-canadensolide, and canadensolide Tetrahedron, 64 (10). pp. 2359-2368. ISSN 0040-4020

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00404...

Related URL: http://dx.doi.org/10.1016/j.tet.2008.01.009

Abstract

A simple strategy has been developed for the synthesis of both enantiomers of nor-canadensolide, epi-nor-canadensolide, and an intermediate to canadensolide. An orthoester Claisen rearrangement of an appropriately constructed allyl alcohol derivative prepared from R-(+)-2,3-di-O-cyclohexylidine glyceraldehyde followed by epoxidation of the resulting unsaturated esters produced hydroxy-lactones, which on oxidation gave keto-lactones. Stereoselective reduction of the keto-carbonyl using either a chelation controlled or a non-chelation controlled process led to the natural or the epi-series, respectively. The interplay of the electronic effect between the polar groups and the steric effect of the β -substituent during reduction of the keto-lactones turned out to be the key factors in deciding the stereochemical outcome. Regeneration of the aldehyde functionality latent in the ketal moiety of the hydroxy-lactones provided the lactols, which on oxidation gave the bis-lactones.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Asymmetric Synthesis; Bis-lactones; Chelation; Stereocontrol
ID Code:12367
Deposited On:10 Nov 2010 06:21
Last Modified:12 Feb 2011 11:07

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