Hey musmusculus
I don't know if this is of any help to you, but i found an article where they prepare 4-epidoxycycline. The reference is:
Kertscher, H.-P.; Habermann, A.; Pohle, R.; Tauchert, H.; Hennig, L.; Eger, K. Preparation and characterization of 4-epidoxycycline. Scientia Pharmaceutica (1998), 66(4), 287-296.
Rico