For example, in a new application, it is unnecessary to write the preparation method of substance A, because substance A is an existing technology. If you write it, the scope will be narrowed, so it must be completed according to the preparation method of substance A, which is considered infringement. What if there are other preparation methods of substance A?
my suggestion is that it is not written in the independent claim, but it can be written in the right or in the specification. For example, it is written in the example: This application provides one of the preparation methods for preparing substance A, and the steps are as follows. . . blabla。
when writing, other issues should be considered: for example, whether the substance A is a freely available substance, and whether the preparation method in another application is the only one that can be prepared in the prior art..