Complex sentence: The synagogue was designed by Jewish Berlin-born architect Alexander Saeltzer, who was engaged in February 1849, and who also later designed the original Astor Library (now The Public Theater) in 1851 and the Academy of Music on Astor Place in 1854.
Split into simpler sentences: The synagogue was designed by Jewish Berlin-born architect Alexander Saeltzer, who was engaged in February 1849. Saeltzer also later designed the original Astor Library (now The Public Theater) in 1851, and the Academy of Music on Astor Place in 1854.