Alexander Salomon de Leeuw grew up in a well-to-do, liberal family. He completed the his education at the Barlaeus gymnasium in Amsterdam and enrolled in 1918 at the Municipal university of Amsterdam to study law. In 1921 he finished his undergraduate years.
Impressed by the Russian Revolution, Alexander Salomon de Leeuw joined the Union of Revolutionary-Socialist Students of the Netherlands. In 1922 he joined the Communist Party of the Netherlands, later known as the CPN. Alexander de Leeuw wrote several brochures and contributed to various periodicals.
During the war, Alexander de Leeuw went into hiding at several addresses. On 18 May 1941 he was arrested and taken to Schoorl concentration camp. He was brought to camp Amersfoort in September 1941. In camp Amersfoort Alexander de Leeuw was an interpreter for a group of Kyrgyzian inmates who were taken prisoner of war by the German army in the Soviet Union. De Leeuw spoke Russian and moved to their barrack. In July 1942 he was deported to Auschwitz.
B. Braber, Zelfs als wij zullen verliezen. Joden in verzet en illegaliteit in Nederland 1940-1945 (Amsterdam, 1990) 108-109
More infromation on Alexander Salomon de Leeuw can be found in Biografisch Woordenboek van het Socialisme en de Arbeidersbeweging in Nederland[in Dutch]. At the website of the IISH some letters of Alexander Salomon de Leeuw are shown.
In addition, a Jokos file (number 34847) on this person is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.