Synthese d'antibiotiques triterpeniques a partir d'acides biliaires-II

Synthesis of Apocholic Acid Derivatives by Photochemical Rearrangement of 12-Oxo-steroids

“…3 a, 12 a,24-trihydroxy-5ß-14a-cholane (2) 10 g (25.51 mmol) deoxycholic acid 1 in 400 ml THF were refluxed with 3 g (79.0 mmol) LiAlH 4 for 3 h. The excess of hydride was destroyed carefully with THF/water. After acidification with diluted HCl 8.8 g (19.1 mmol) of 3 were oxidised with 9 ml Jones-reagent (6.7 g Cr0 3 in 6 ml H 2 S0 4 /19 ml water) in 600 ml acetone at R.T. for 30 min.…”

14-Methyl steroids. Part 5. Structural features influencing stereoselectivity of 14-methylation of 15-oxo-19-norsteroids: synthesis of 14α-methyl-19-norprogesterone

“…3-Metho.u)i-14P-estra-1,3,5 ( 10),8-tetraen-15-one ( 5). -A mixture of the 14x-bromo 15-ketone (4) (240 mg), lithium bromide (500 mg), and lithium carbonate (400 mg) in dimethylformamide (15 ml) was stirred at 100 "C under nitrogen for 16 h. The mixture was cooled, diluted with water, and extracted with ethyl acetate, and the product was chromatographed on silica gel (30 g), with ethyl acetate-hexane (3:7) as eluant, to give the A8-15-ketone (5) ( Base-mediated Methylation of the A8-1 5-Ketone (5).-A Msolution (6 ml) of potassium t-butoxide in t-butyl alcohol was added to a stirred solution of the A'-15-ketone (5) (155 mg) in t-butyl alcohol (15 ml) at 30 "C under nitrogen. After 5 min, methyl iodide (1 ml) was added and the mixture was stirred at 30°C for 1 h. Aqueous sodium sulphite was added and the product was isolated by extraction with ethyl acetate.…”