• P L Sawhney

      Articles written in Proceedings – Section A

    • Nuclear oxidation in flavones and related compounds - Part XXXII. Some coumarin derivatives

      P L Sawhney T R Seshadri T R Thiruvengadam

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      It is suggested that umbelliferone is a fundamental compound in the biogenesis of coumarins and that other important hydroxycoumarins involve further stages of oxidation. In support of this idea experiments are described for the preparation from umbelliferone of æsculetin byp-oxidation and daphnetin byortho-oxidation. From either of these dihydroxycoumarins, 6:7:8-trihydroxycoumarin can be prepared. Limettin would, however, appear to have a different origin. The possible evolution of fraxinol from limettin byp-oxidation is supported by persulphate oxidation experiments using 4-methyl limettin. 4-Methyl fraxinol has also been synthesised from 2:6-dimethoxyquinol and acetoacetic ester.

    • Partial methyl ethers of polyhydroxy coumarins - Part I. Partial methylation of 5∶7-dihydroxy-4-methyl coumarin

      P L Sawhney T R Seshadri

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      Earlier investigations have shown that partial methylation of the 7-position of 6∶7-dihydroxy coumarin is definitely possible. Claims were made by Schmid that in 5∶7-dihydroxy-4-methyl coumarin also partial methylation takes place in the 7-position. But no proof was provided. This has now been given by the ethylation of the partial methyl ether and subjecting it to nuclear oxidation and final ethylation. The product is found to be 7-methoxy-5∶6-diethoxy-4-methyl coumarin which has also been made by an independent and unambiguous method for purposes of comparison. The constitution of the partial methyl ether is thus established as 7-methoxy-5-hydroxy-4-methyl coumarin.

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