Method for producing modified conjugated diene-based polymer, modified conjugated diene-based polymer, polymer composition, crosslinked body, tire and compound

A modified conjugated diene-based polymer of formula (3):

• wherein R2 is a hydrocarbyl group having 1 to 20 carbon atoms, R6 is a hydrocarbyloxy group having 1 to 20 carbon atoms or a modified or unmodified conjugated diene-based polymer chain, R4 is an alkanediyl group having 1 to 20 carbon atoms, and Z is a group represented by the following formula (4) or (5), R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms or an m-valent group having 1 to 20 carbon atoms, which has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom and does not have an active hydrogen;
• n is an integer of 1 to 3 and m is an integer of 2 to 10, and a plurality of R2, R4, R6, Z, and n are optionally the same or different:
• wherein R1 is a hydrogen atom or a hydrocarbyl group and Poly is a modified or unmodified conjugated diene-based polymer chain;
• and “*” represents a bond to R5.