In accordance with the present invention, 21-lower alkoxyoxalylprogesterone is prepared in high yield by the lower alkoxyoxalylation of 3-methoxypregna-3,5-diene-20-one. The 3-methoxypregna-3,5-diene-20-one is prepared from progesterone by methods well known in the art. The 3-methoxypregna-3,5-diene-20-one is lower alkoxyoxalylated with an alkoxide base and the corresponding lower alkyloxalate in a suitable solvent. The alkoxide base consists of a lower alkoxide with an alkali metal counter ion. The lower alkyl group of both the alkoxide and oxalate should be the same and also are the same as the group to be added to the 21 position of the 20-keto steroid, the lower alkyl group contains 1 to 6 carbon atoms. The lower alkoxyoxalylation reaction can be carried at any temperature below the boiling point of the solvent and for a period of 2-20 hours depending on the temperature at which the reaction is carried out. For example, at elevated temperatures the rate of reaction is sufficiently fast to complete the lower alkoxyoxalylation in 2 to 4 hours whereas if the reaction is carried out at ambient temperatures complete reaction can require 14 to 20 hours. The reaction is preferably carried out under an inert atmosphere such as a nitrogen or argon atmosphere.
根据本发明,通过对3-甲氧基孕烷-3,5-二烯-20-酮进行低烷氧基草酰化,可以高产率地制备21-低烷氧基草酰
孕酮。3-甲氧基孕烷-3,5-二烯-20-酮是通过艺术中已知的方法从
孕酮制备的。3-甲氧基孕烷-3,5-二烯-20-酮与碱
金属对离子的低烷氧基碱和相应的低烷氧基
草酸酯在适当的溶剂中进行低烷氧基草酰化。碱
金属对离子的低烷氧基碱由含有碱
金属对离子的低烷氧基组成。碱
金属对离子的低烷氧基碱和
草酸酯的低烷基基团应该相同,也应该与要添加到20-
酮类固醇的21位的基团相同,低烷基基团含有1至6个碳原子。低烷氧基草酰化反应可以在溶剂的沸点以下的任何温度下进行,反应时间为2-20小时,取决于反应进行的温度。例如,在升高的温度下,反应速率足够快,可以在2至4小时内完成低烷氧基草酰化,而如果在室温下进行反应,则完全反应可能需要14至20小时。最好在惰性气氛下进行反应,如氮气或
氩气氛。