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Featured researches published by N. Narasimhachari.


PROC INDIAN ACAD SCI-MATH SCI | 1948

A new effect of hydrogen bond formation

Ishwar-Dass; N. Narasimhachari; T. R. Seshadri

SummaryPast records indicate that an 8-hydroxyl group in a flavone is involved in chelation but it is of a weak nature. 7-Methoxy-8-hydroxy flavanone can be easily obtained by the partial methylation of 7∶8-dihydroxy flavanone or the partial demethylation of 7∶8-dimethoxy flavanone, and can also be directly obtained from gallacetophenone-4-methyl ether. Its preparation and properties indicate the existence of stronger chelation involving the 8-hydroxyl group. Similar experiments have been done on the preparation of 7-methoxy-8-hydroxy chromone and isoflavone. Though the partial demethylation of 7∶8-dimethoxy compounds has been successful, partial methylation of the dihydroxy compounds has not been possible in these cases. The properties of the products also indicate weaker chelation in the chromone and isoflavone just as in the corresponding flavone. In the course of the synthesis of 7-methoxy-8-hydroxy flavanone and chromone independently for purpose of comparison the preparation of the intermediate gallacetophenone 4-methyl ether has been re-investigated and a convenient method has been worked out.


PROC INDIAN ACAD SCI-MATH SCI | 1948

A new effect of hydrogen bond formation (chelation)

N. Narasimhachari; D. Rajagopalan; T. R. Seshadri

SummaryFor the preparation of flavanones having a 2′-methoxy group the acid method of chalkone condensation employing benzoates of hydroxy ketones is convenient. 5-Hydroxy-2′-methoxy flavanone and 5∶7-dihydroxy-2′-methoxy flavanone have thus been prepared. By demethylating the former with aluminium chloride 5∶2′-dihydroxy flavanone is obtained which undergoes only partial methylation in the 5-position even with excess of the reagent confirming that the 2′-hydroxyl is highly resistant. Synthetic 5∶7-hydroxy-2′-methoxy flavanone and its derivatives made by us and by Shinoda and Sato agree, but they do not agree in their properties with natural citronetin and its derivatives.5-Hydroxy-2′-methoxy flavone does not undergo isomeric change under ordinary conditions of demethylation. 5∶2′-dihydroxy flavone undergoes partial methylation smoothly in the 2′-position thus showing the existence of marked difference between flavanones and flavones.


Proceedings of the Indian Academy of Sciences - Section A | 1953

Synthetic experiments in the benzopyrone series

N. Narasimhachari; T. R. Seshadri


Archive | 1949

Synthetic experiments in the benzopyrone series. Part IX. Partial demethylation of chalkones: a synthesis of sakuranetin

N. Narasimhachari; T. R. Seshadri


Archive | 1948

Nuclear oxidation in the flavone series. Part VIII. 7 : 8-Dihydroxy-flavone and-flavonol

N. Narasimhachari; L. Ramachandra Row; T. R. Seshadri


Archive | 1953

Synthetic experiments in the benzopyrone series. Part XLIII. Preparation of 3-hydroxy flavanones

Om Parkash Goel; N. Narasimhachari; T. R. Seshadri


Archive | 1953

Synthetic experiments in the benzopyrone series. Part XLII. A new synthesis of 5:6: 7-trihydroxy isoflavone derivatives

V. B. Mahesh; N. Narasimhachari; T. R. Seshadri


PROC INDIAN ACAD SCI-MATH SCI | 1952

A new effect of hydrogen bond formation (chelation) Part IV. Abnormal behaviour of 2'-hydroxy flavanones

N. Narasimhachari; D. Rajagopalan; T. R. Seshadri


PROC INDIAN ACAD SCI-MATH SCI | 1952

Nuclear oxidation in flavones and related compounds. Part XLIV. New synthesis of polyhydroxy coumarins and a note on trimethyl dihydro-psoralene

V. D. Nageswara Sastri; N. Narasimhachari; P. Rajagopalan; T. R. Seshadri; T. R. Thiruvengadam


Archive | 1952

A new effect of hydrogen bond formation (chelation) Part VI. Synthesis of 5-hydroxy-2'-methoxy flavanone and 5:7-dihydroxy-2'-methoxy flavanone

N. Narasimhachari; D. Rajagopalan; T. R. Seshadri

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