A new and convenient synthesis of the 17α,21-diacetoxy-20-oxopregnane side-chain
Abstract
A convenient ‘one-pot’ synthesis of the corticosteroid side chain has been developed. 20-Oxopregnane oximes have been converted into 20-acetylamino-17(20)-ene derivatives, which with lead tetra-acetate in dry benzene afford 17α-acetoxy-20-acetylimines. The latter are rearranged by acid to 20-enamides [as (IV)]. Further reaction with lead tetra-acetate then introduces an acetoxy-group at C-21. The 20-acetylimines are hydrolysed to the corresponding ketones by aqueous acid. Overall yields are high. Some preliminary experiments with 16α- and 16β-methylpregnanes are outlined.