In 1510 the Jewish doctor Mosche moved from Aschaffenburg to Frankfurt. He had previously worked as a doctor in a hospice in Rome. At the request of the counts of Königstein, NassauSolms, and Solms, he was given right of residence in Frankfurt and was allowed to settle there. He was also granted permission to leave the town at will, but then only to treat his aristocratic clients, who included the count of Hanau. As a result of his experience in Italy, Mosche of Aschaffenburg was known as a specialist in the treatment of syphilis, quickly earning a good reputation. In 1523 Mosche was employed as a doctor by the city of Frankfurt, the last Jew to hold this position. He was not actually accorded the same status as his Christian colleagues, and was only permitted to treat minor town officials and patients in the Hospice of the Holy Ghost, but he did receive a salary from the Town. When appointed he moved into the house Roter Löwe. After 1528 the city council allowed him to leave the Judengasse and the city at night, since he frequently had to treat the nobility in the surrounding area. Mosche from Aschaffenburg is explicitly described as practising only as a doctor: he did not engage in pawnbroking. He became involved in numerous disputes with the Jewish community and its members, and complained to the city council about it. He was accused of striking the Jewish innkeeper, Knebel, and was frequently reprimanded for slander.
At least two (and possibly three) of his sons carried on the medical practice at their father's home: Abraham and Isaac zum Löwen. The Aschaffenburg family thus became the most famous family of doctors in the 16th century.