Delta(23)-22-Oxo steroids were synthesized via 1,3-dipolar cycloaddition of steroidal nitrile oxides to low-molecular dipolarophiles. Cycloaddition of 2-propynyl bromide to 20-carbonitrile oxide, followed by hydrogenation of the isoxazole derivative thus formed gave 22-enamino-24-keto steroid. The latter was then converted into the target enones via several pathways. Compounds with unnatural configuration of the C-20 atom can also be obtained. Delta(23)-22-Oxo steroids were also synthesized through isoxazole derivatives.
Delta(23)-22-Oxo steroids were synthesized via 1,3-dipolar cycloaddition of steroidal nitrile oxides to low-molecular dipolarophiles. Cycloaddition of 2-propynyl bromide to 20-carbonitrile oxide, followed by hydrogenation of the isoxazole derivative thus formed gave 22-enamino-24-keto steroid. The latter was then converted into the target enones via several pathways. Compounds with unnatural configuration of the C-20 atom can also be obtained. Delta(23)-22-Oxo steroids were also synthesized through isoxazole derivatives.