| 摘要 |
The invention relates to a process for the preparation of 17 alpha -pregnane-21,17-carbolactones of the formula I <IMAGE> in which R1 and R2 are hydrogen or together are a beta -methylene group, and the formula segment <IMAGE> represents the radicals <IMAGE> characterised in that compounds of the formula II <IMAGE> in which R1, R2 and the formula segment <IMAGE> have the abovementioned meanings, are reacted, depending on the desired meaning of A1, with a brominating reagent and LiBr/Li2CO3 or, if a 3-methoxy-3,5-diene structure is to be present in the compounds of the formula I, with LiBr/Li2CO3.
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