Scientia Sinica

No. | CHANG: STUDIES ON FUSED RING SYSTEMS II 55

(2) With concentrated sulfuric acid as cyclization agent—To 800 ml of concentrated sulfuric acid which was cooled with ice-salt mixture to -8°, 100 g of the crude keto malonic ester (V) was slowly added with vigorous stirring. After the addition, the temperature of the mixture was gradually raised to 0° and maintained at this temperature for about 10 hours. Then the mixture was poured into about 1 kg of ice with stirring and yellow oil was liberated which was extracted three times with ether. After the ether was distilled off, the dark oily residue was worked up according to the method described for the hydrofluoric acid cyclization in the above experiment. The yield of the dibasic acid (VII) amounted to 32 g; m.p. 179-185° (with decomposition), After recrystallization from benzene-dioxane, the acid melted at 188-190° alone or when mixed with a sample prepared by Bachmann and coworkers.

y-(6-methoxy-2-carboxy-1,2,3,4-tetrahydro-l-naphthyl)-butyric Acid (VIII) —This acid was prepared according to the method of Bachmann and coworkers". A solution of 8.7 ¢ of the unsaturated dibasic acid (VII) (m.p. 188-190°) in 150 ml of purified acetic acid was hydrogenated in the presence of 1 g of 5% palladium-carbon at normal temperature and pressure. After three hours, the amount of hydrogen absorbed was almost complete (actual uptake 730 ml; theoretical uptake 731 ml). After the catalyst was filtered off and the solvent removed at reduced pressure, a colourless solid was recrystallized from benzene-methyl alcohol, m.p. 156-158° alone or when mixed with a sample prepared by Bachmann and coworkers"); yield 78g (90% of the theoretical). .

Resolution of y-(6-Methoxy-2-carboxy-l, 2, 3, 4-tetrahydro-l-naphthyl)butyric Acid —To a solution of 79 g of brucine in 1,200 ml of anhydrous methyl alcohol heated on a steam bath, 29.2 g of y-(6-methoxy-2-carboxy-l,2,3,4tetrahydro-I-naphthyl)-butyric acid (m.p. 156-158°) was added slowly. After all of the acid had been added, heating was continued for about half an hour. The mixture was filtered and the clear filtrate was put in the ice box overnight. Plenty of needle-like crystals separated out. This was filtered and amounted to 49g (first fraction of the di-brucine salt).. After this fraction ~ was recrystallized from anhydrous methyl alcohol for three times, its melting point and rotation became constant; m.p. 161-167° (began to shrink at 145°). Rotation. A solution of 0.1 g of the dibrucine salt in 10 ml of absolute ethyl alcohol gave a—0.74, [@]>—74.0° —

Analysis. Calcd. for Cgs2H72.NuOis: C, 68.87; H, 6.70; INS, DSL Found: C, 69.10; H, 6.89; N, 5.02.

The filtrate from the first fraction of the di-brucine salt was concentrated to about 500 ml. After being cooled with ice, needle-like crystals separated out from the solution. This was filtered, dried and amounted to 8 g (second fraction).