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"He was important as a witness and as a fighter for the rights of former slave workers. We all loved him," said Henry Mathes, who heads an organization that has fought for reparations from IG Farben.

In 1943, Frankenthal's family was taken in cattle cars to Auschwitz. Frankenthal and his brother, Ernst, never saw their parents again.

Both boys were selected for work by Dr. Josef Mengele and the director of IG Farben. In 1945, Soviet soldiers liberated the brothers from Theresienstadt.

Legal obstacles fed by anti-Semitism prevented them from recovering their family home or receiving reparations for their father's butcher shop. They received instead a small sum, Frankenthal reported in his book.

In August, Frankenthal, the vice president of the International and German Auschwitz Committees and a member of the Central Council of Jews in Germany, made headlines when he was forcibly prevented from finishing his statement at the IG Farben shareholders meeting.

"When he spoke about the Nazi era and about his personal history he was often quite angry, though he surely had told all these stories again and again," Mathes said. "In private he was such a warm, nice person. So there must have been two hearts beating in his breast."