No abstract

No abstract

No abstract

Dehydrobromination of 7-Keto-8-bromocholesteryl Acetate (IX).-A solution of 1 g. of IX and 30 cc. of pyridine was refluxed for 7 hours and the reaction mixture was treated in the usual manner; the reddish-brown oily product was chromatographed through a column of 50 g. of alumina (Brockmann Grade II) with a petroleum ether-benzene (1:1) solution (200 cc.). The eluate was fractionated into 40 cc. each.Fractions 3 and 4 afforded a solid which after crystallization from alcohol gave 80 mg. of colorless crystals, m.p. 119-120°, identical with V.Development of the column with a benzene-ether (1:1) mixture afforded 90 mg. of III, m.p. 152-153°. Preparation of 7-Keto-A3'6-8(9,-cholestatriene (V) from 7-Keto-A3'5-cholestadiene (XI).-To a solution of 4 g. of XI in 25 cc. of carbon tetrachloride, 2 g. of NBS and 150 mg. of dibenzoyl peroxide were added, and the mixture was refluxed on a water-bath, with protection from moisture, with irradiation of a 375-watt infrared lamp at a distance of 40 cm.Most of the NBS was converted to succinimide within 30 minutes, and the reaction was complete in about 50 minutes. The cooled reaction mixture was filtered, and the filtrate was evaporated to a brown, oily residue which could not be crystallized. Therefore, 2 g. of this bromide was dissolved in 30 cc. of pyridine, the mixture was refluxed for 6 hours, and the cooled mixture was poured into ice-cooled dilute hydrochloric acid. This was extracted with ether, the ether layer was washed consecutively with 10% hydrochloric acid and water, dried, and the solvent was removed under reduced pressure.The brown oily residue (1.2 g.) was dissolved in 200 cc. of petroleum ether-benzene (1:1) and passed through a column containing 40 g. of alumina (Brockmann Grade I/II). The column was eluted with 200 cc. of petroleum ether-benzene and the eluate was fractionated into 40 cc. each. The oily residue obtained from fractions 2 and 3 was recrystallized from ethanol; colorless needles (XV), m.p. 150-151°, X®'°H 294 µ (£ 10,700), yield 250 mg.

No abstract