Synthesis of 7- and 12-hydroxy- and 7,12-dihydroxy-3-keto-5β-cholan-24-oic acids by reduction of 3,7-, 3,12- and 3,7,12-oxo derivatives
摘要:
7alpha-, 12alpha-, 12beta-Hydroxy and 7alpha,12alpha- and 7alpha,12beta-dihydroxy-3-ketocholanoic acids were prepared in satisfactory yields protecting the 3-keto group as dimethyl ketal and subsequent reduction with sodium borohydride of the corresponding 7- and 12-oxo functionalities. The same procedure gave also 3,12-diketo-7alpha-hydroxy-cholanoic acid.
12-diketo-5 beta-cholan-24-oic acid (7,12-diketolithocolic acid) as the main product. A number of different chemical reductions were carried out on DHCA; among them hydrogenation with Raney Nickel in water under high-intensity ultrasound proved highly regio- and stereoselective, yielding 7,12-diketolithocolic acid exclusively. (1)H and (13)C resonances were assigned in details thanks to a series of 1D and 2D
7alpha-, 12alpha-, 12beta-Hydroxy and 7alpha,12alpha- and 7alpha,12beta-dihydroxy-3-ketocholanoic acids were prepared in satisfactory yields protecting the 3-keto group as dimethyl ketal and subsequent reduction with sodium borohydride of the corresponding 7- and 12-oxo functionalities. The same procedure gave also 3,12-diketo-7alpha-hydroxy-cholanoic acid.