• L Ponniah

      Articles written in Proceedings – Section A

    • Experiments on the synthesis of coumaryl styrenes

      L Ponniah T R Seshadri

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      A number of hydroxy and methoxy coumarin acetic acids have been prepared by the method of Dey and Row with a view to convert them into the corresponding coumaryl styrenes. Except the simplest of them,i.e., 7-hydroxy coumarin-4-acetic acid, the others do not undergo the condensation with aromatic aldehydes, but suffer only decarboxylation. A study of the γ-acetates obtained by the high temperature acetylation of simpler chalkones and flavanones indicates that they are not coumaryl styrene derivatives, though their compositions agree with such.

    • Nuclear oxidation in flavones and related compounds - Part XLII. A synthesis of 6-hydroxy pyrylium salts of the gesneridin type

      L Ponniah T R Seshadri

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      Polyhydroxy benzadehydes are prepared by nuclear oxidation ofo-hydroxy benzaldehyde derivatives with alkaline persulphate and condensed withp-hydroxy andp-methoxy acetophenones to yield 6-hydroxy pyryium salts.

    • Nuclear oxidation in flavones and related compounds - Part XLV. A synthesis of carajuridin chloride and carajurin

      L Ponniah T R Seshadri

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      The synthesis of carajuridin chloride and carajurin has been carried out starting with 6-O-methyl phloroglucinaldehyde, preparing 2:4:5-trihydroxy-6-methoxy benzaldehyde as an intermediate and condensing the latter withp-methoxy acetophenone. Identity with the natural products has been established by direct comparison using melting points, chromatography and colour reactions. This synthesis confirms the constitution proposed by Chapman, Perkin and Robinson for carajurin. 6:7-Dihydroxy-4′-methoxy flavylium chloride exhibits colour reactions very similar to carajuridin and the isomeric 7:8-dihydroxy-4′-methoxy flavylium chloride possesses very different properties thus excluding other possibilities for the constitution of carajuridin.

    • Synthesis of isocarajuretin hydrochloride

      L Ponniah T R Seshadri

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      7-Hydroxy-5:8:4′-trimethoxy flavylium chloride has now been prepared and subjected to demethylation with hydriodic acid. The resulting flavylium iodide and the colour-base (Isocarajuretin) and the flavylium chloride obtained from it, are different from carajuretin and its salts. Hence it is concluded that no isomeric change takes place during the demethylation of derivatives of 5:7:8-hydroxy-flavylium salts related to flavones, supporting the constitution of carajurin, given by Chapman, Perkin and Robinson.

    • A synthesis of carajurone hydrochloride

      L Ponniah T R Seshadri

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      The condensation of 1: 2: 3: 5-tetrahydroxy benzene with anisoyl acetaldehyde takes place in an abnormal way and gives rise to 5: 7: 8-trihydroxy-4′-methoxy flavylium chloride. By using 2: 6-dibenzyloxy quinol, 5: 7-di-benzyloxy-6-hydroxy-4′-methoxy flavylium chloride is obtained and subsequent debenzylation yields carajurone hydrochloride; by the action of sodium acetate, the colour-base carajurone is obtained.

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