| 摘要 |
<p>NEW MATERIAL:Compounds of formula I (R<1> is H, hydroxyl-protecting group; R<2> is H, hydroxyl, protected hydroxyl; R<3> and R<4> are H or incorporate to represent C-C bonds). EXAMPLE:25-Brom-3beta-hydroxy-24-oxocholest-5-ene. USE:Synthetic intermediates of various kinds of activated vitamin D3, e.g., 24,25- dihydroxyvitamin D3. PREPARATION:The reaction between a 24-oxocholesterol derivative of formula II and a bromide of formula III (R<5> and R<6> are H, lower alkyl), e.g., 2-bromo-2- cyano-N,N-dimethylacetamide, is conducted in a solvent, e.g., benzene, preferably at 20-200 deg.C to give the compound of formula I. The amount of the bromide of formula III used is 0.5-2.0, preferably 0.8-1.5 moles per mole of the compound of formula II.</p> |
