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PROC INDIAN ACAD SCI-MATH SCI | 1936

Geometrical inversion in the acids derived from the coumarins

T. R. Seshadri; P. Suryaprakasa Rao

Coumaric acids which ordinarily form hydroxystyrenes on heating yield the corresponding coumarins when heated in the presence of mercuric oxide or chloride. The scope of the use of concentrated sulphuric acid and alcohol saturated with hydrogen chloride for producing trans tocis inversion has been examined. The former is useful for nitrocoumaric acid whereas the latter is suitable for coumaric and methylcoumaric acids. Mercuric chloride in neutral aqueous solution has been found to be very satisfactory for both types of acids.


Proceedings of the Indian Academy of Sciences - Section A | 1943

Chemical components of indian tulip (Thespasia populnea) flowers

K. Neelakantam; P. Suryaprakasa Rao; T. R. Seshadri

SummaryA sample of the flower-petals ofThespasia populnea is found to contain populnin (0·33%), populnetin (0·07%) and herbacetin (mostly as its glucoside, 0·03%). The proportions vary with different samples depending on seasonal and other factors. Besides these three yellow pigments, a colourless phenolic compound called populneol is also present (0·16%).Populnetin seems to be a new tetrahydroxy flavone and populnin is its monoglucoside.


PROC INDIAN ACAD SCI-MATH SCI | 1941

Constitution of cannabiscitrin

P. Suryaprakasa Rao; T. R. Seshadri

SummaryThe final constitution of cannabiscitrin has been established. It is a monoglucoside of the flavonol cannabiscetin, carrying the sugar group in the side phenyl nucleus in the 3′-position. This has been arrived at from the following considerations:—It gives the gossypetone reaction and after complete methylation and hydrolysis, it yields a pentamethyl cannabiscetin which on decomposition produces 4∶5-dimethyl gallic acid. The same acid is also obtained by first decomposing cannabiscitrin with alkali, and then subjecting the products to methylation and subsequent hydrolysis. Thus the glucoside belongs to an unusual type and resembles butrin.


PROC INDIAN ACAD SCI-MATH SCI | 1941

Isolation and constitution of quercetagitrin, a glucoside of quercetagetin

P. Suryaprakasa Rao; T. R. Seshadri

SummaryQuercetagitrin, a monoglucoside of quercetagetin, has for the first time been isolated from the flowers of the African Marigold (Tagetes erecta). It is not a 3-glucoside since it gives a red precipitate with lead acetate and does not undergo easy hydrolysis with acids. Further it is easily oxidised in cold alkali, and after methylation the products of decomposition yield veratric acid. The glucose group, therefore, is not present in the side phenyl nucleus. By complete methylation and subsequent hydrolysis of the glucoside, a pentamethyl quercetagetin is obtained. This ether is a new compound, and differs from 3∶6∶7∶3′∶4′-pentamethyl quercetagetin in all its properties, and hence the free hydroxyl group in it is in either the 6th or the 7th position. The allyl ether of this new pentamethyl quercetagetin smoothly undergoes the Claisen Rearrangement, indicating thereby that the ortho-position with respect to the allyloxy group is unsubstituted. Hence the allyl ether should be 3∶5∶6∶3′∶4′-pentamethyl-7-allyl quercetagetin, and the new pentamethyl ether should have the constitution of 3∶5∶6∶3′∶4′-pentamethyl quercetagetin. Consequently quercetagitrin is the 7-glucoside of quercetagetin.


PROC INDIAN ACAD SCI-MATH SCI | 1941

Constitution of butrin

P. Suryaprakasa Rao; T. R. Seshadri

SummaryOn treatment with diazomethane, butrin gives rise to a monomethyl ether which yields on hydrolysis with acids a mixture of 4′-O-methylbutin and 4′-O-methylbutein, the latter being the major component. The constitutions of these two products have been established by alkaline oxidation, yielding isovanillic acid and comparison with synthetic samples. It is, therefore, concluded that butrin is 3′: 7-diglucoside of butin, and thus it is the first instance of a glycoside to contain the sugar residues in two different positions amongst the group of anthoxanthins and also the first instance to carry a sugar group in the side phenyl nucleus amongst both anthoxanthin and anthocyanin pigments.


PROC INDIAN ACAD SCI-MATH SCI | 1940

Methylation of hydroxy flavonols using methyl iodide and potassium carbonate

P. Suryaprakasa Rao; P. Prabhakara Reddy; T. R. Seshadri

SummaryBy the action of methyl iodide and potassium carbonate, quercetin underwent complete methylation, while herbacetin and gossypetin yielded 3∶7∶8∶4′-tetramethyl ether and 3∶7∶8∶3′∶4′-pentamethyl ether respectively. This reagent, therefore, resembles diazomethane in the methylation of the naturally occurring flavonols.


PROC INDIAN ACAD SCI-MATH SCI | 1944

Synthesis of Hibiscetin

P. Ramachandra Rao; P. Suryaprakasa Rao; T. R. Seshadri

SummaryA convenient method of preparing 2∶4-dihydroxy-ω∶3∶6-trimethoxyacetophenone (I) directly from 2∶6-dibenzyloxy-1∶4-dimethoxybenzene is described. By the condensation of (I) with the sodium salt and anhydride of trimethylgallic acid, 7-hydroxy-3∶5∶8∶3′∶4′∶5′-hexamethoxyflavone (II) is obtained. Methylation of (II) yields a heptamethyl ether (III) identical with heptamethyl hibiscetin. Demethylation of (II) gives rise to a heptahydroxy flavone (IV) which is found to be identical with hibiscetin in all its properties and reactions. The constitution of hibiscetin is therefore confirmed by synthesis as 3∶5∶7∶8∶3′∶4′∶5′-heptahydroxy flavone.


PROC INDIAN ACAD SCI-MATH SCI | 1941

Colouring matter of the flowers ofHibiscus cannabinus: Constitution of Cannabiscetin

K. Neelakantam; P. Suryaprakasa Rao; T. R. Seshadri

SummaryThe colouring matter of the flower petals ofHibiscus cannabinus consists mostly of the glucoside cannabiscitrin along with small quantities of the corresponding aglucone cannabiscetin. The properties and reactions of these two substances are described along with those of some of their derivatives.Cannabiscetin forms a hexaacetate and a hexamethyl ether. It is a flavonol exhibiting similarities with gossypetin and herbacetin particularly in regard to alkali colour reactions and gossypetone reaction. It yields gallic acid on being subjected to alkali fission, its methyl ether producing trimethyl gallic acid. It is, therefore, concluded to be 3:5:8:3′:4′:5′ hexahydroxy flavone.


Archive | 1942

Pigments of the flowers of Hibiscus sabdariffa isolation of sabdaretin, a new hydroxyflavone

P. Suryaprakasa Rao; T. R. Seshadri


Archive | 1943

Pigments of cotton flowers. Part IX. A note on the occurrence of populnetin in Indian cotton flowers

P. Suryaprakasa Rao; T. R. Seshadri

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