A laevo-rotatory modification of quercitol / by Frederick B. Power and Frank Tutin.

  • Power, Frederick B. (Frederick Belding), 1853-1927.
Date:
[1904]
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: A laevo-rotatory modification of quercitol / by Frederick B. Power and Frank Tutin. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    chemically; but, since rf-quercitol has [a]r, +24’16°, the one cannot be the optical antipode of the other. Pentahydroxyhexahydrobenzene has four asymmetric groupings, and eight optically active modifications are therefore possible, which may be represented as follows : + + + + — 4 4“ + -f - -1- 4- — + - + + + + By uniting these four pairs, the corresponding racemic modifications would be obtained. The following two unresolvable inactive modifica- tions are also possible : “ — + and + — + — . Until a further number of these isomerides of quercitol are known, it will be impossible to assign a definite configuration either to fZ-quercitol or to the ^-quercitol isolated from Gymnema sylvestre. Experiment al. IQuercitol, The leaves of Gymnema sylvestre were extracted with hot alcohol and the liquid concentrated to a viscid syrup. Water was then added and the greater part of the remaining alcohol removed on the water- bath. After being allowed to cool, the precipitated resins were removed by filtration. Sulphuric acid was added to the clear filtrate until no further precipitate was produced, and this precipitate, which soon agglomerated to a resinous mass, was likewise removed by filtra- tion. The free sulphuric acid was then removed by barium hydroxide, a slight excess of basic lead acetate subsequently added to remove the colouring matter, and the combined precipitates filtered oft’. After depriving the filtrate of lead by means of hydrogen sulphide, it was concentrated under reduced pressure to the consistency of a viscid syrup and then diluted with alcohol, when, after a few days, the ^-quercitol separated in a nearly pure, crystalline form, which, after being filtered at the pump, thoroughly washed with alcohol, and recrystallised from dilute alcohol, was obtained in a perfectly pure state. The amount of this substance contained in the air-dried leaves is 0‘6 per cent. ^-Quercitol melts at 174°. A determination of its specific rotatory power in aqueous solution gave the following result: a - 2°59'; 1 dcm. ; c = 4‘035 ; [a]u - 73‘9°. It is readily soluble in water, very sparingly so in alcohol, and insoluble in all other ordinary solvents. It crystallises from water in