Depsides total synthesis

Polyporic acid series. J Chem Soc 1041-1045 Cambie RC (1968) The depsides from Stereocaulon ramulosum (Sw.) Rausch. N Z J Sci 11 48-53 Canonica L, Rindone B, Santaniello E, Scolastico C (1972) A total synthesis of mycophenolic acid, some analogues and some biogenetic intermediates. Tetrahedron 28 4395-4404... 

The more classical chemical procedures of degradation and total synthesis also developed apace with the use of newer reagents and synthetic methods. For instance, the use of condensing reagents trifluoroacetic anhydride and dicyclohexyl-carbodiimide makes the preparation of lichen depsides a relatively straightforward procedure, so that total synthesis is now a common means of strucmral confirmation. 

Total synthesis has provided a definitive method for structural elucidation of all groups of depsides and provides a useful alternative to the classical hydrolytic degradation procedure. Further, in cases where complex mixtures of homologous depsides or simply lack of lichen material make isolation of the new depside impractical, t.l.c. comparisons of synthetic material with the natural mixtures has enabled the identity of a number of new depsides to be established (44, 45). 

The structural elucidation of the new depside 2-O-methylconfluentic acid (237) 190) via the nature of the hydrolysis products has been mentioned previously (Scheme 27). The total synthesis of this compound has also been reported 119) and was the first instance where a depside containing an oxidized side chain had been synthesized. Here additional difficulties arise because of the close proximity of the reactive benzyl ketone... 

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