Scientia Sinica

56 SCIENTIA SINICA Vol, V

The filtrate from the second fraction was concentrated to 150 ml. Upon cooling with ice, nothing separated out from the solution. Then the solvent was blown oft wai air and yellow resinous material was obtained which amounted to 50 g (third fraction). The difference in solubility between this fraction of the di-brucine salt and that of the first fraction is so great that these two fractions can be readily separated from each other. This fraction of the salt was used for the following experiment without further purification.

Liberation of the /-acid (IX) and d-acid (XIII) from the respective salts. —A solution of 38g of the purified first fraction of the dibrucine salt in 300 ml of chloroform was extracted with 2 N potassium hydroxide for 4 times, 50 ml being used each time. The potasstum hydroxide extracts were combined and filtered from any insoluble material. The clear aqueous solution was poured into 100 ml of concentrated hydrochloric acid and a colourless solid separated out which was filtered and washed with water for three times. After being dried, the crude acid amounted to 10g; m.p. 168-170°. After recrystallization from benzene-ethyl alcohol, it melted at 171-172°.

Rotation. A solution of 70 mg of the /-acid in 10 ml of absolute ethyl alcohol gave a—0.86, [a]? —123°.

Analysis. Calcd. for CygHa O05: C, 65.74; H, 6.87. Found: C, 65.65; E7e0:

A solution of 49 g of the unpurified third fraction of the di-brucine salt in 300 ml of chloroform was extracted four times with 2 N potasstum hydroxide, 50 ml being used each time. The potassium hydroxide extracts were combined and filtered. After the clear filtrate was poured into 100 ml of concentrated hydrochloric acid cooled with ice, a slightly yellowish solid separated out. This was filtered and washed three times with water. After being dried, it amounted to 124g; m.p. 168-170°. After recrystallization from benzeneethyl alcohol, the acid formed colourless needles; m.p. 171-172°.

Rotation. A solution of 0.12 g of the d-acid in 10 ml of absolute alcohol gave G@+145, lale +121.

Analysis, Calcd. for CygHaoOs: -C, 65.74; —-H, 6.87. Found: C, 65.67; —+4H, 6.83.

Dimethyl ester of /-y-(6-methoxy-2-carboxy-1,2,3,4-tetrah ydro-l-naphthyl)butyric Acid (X).—To a suspension of 6.0 g¢ of the /-acid (m.p. 168-170°) in a 20 ml of anhydrous ether, an ethereal solution of diazomethane prepared from 20g of N-nitroso-8-methylaminoisobutyl methyl ketone'! was added. After the mixture was left standing at room temperature for one hour, the ether was blown off with air and colourless oil was obtained. This was directly used for the following experiment.