に先立って => before; prior to ~ N2
に[先立「さきだ」]って/に[先立「さきだ」]ち/に[先立「さきだ」]つ => Before A occurs/takes place N2
Time, Situation
最中に => while; during; in the middle of ~ N3
〜がさいご(が最後) => if you do... negative result N1
Decisive (resolute decision)
[最中「さいちゅう」] => In the middle of A N3
Time, Situation
たが[最後「さいご」] => Once A occurs, B happens N1
Information, Report
に先駆けて => prior to; to be the first (pioneer); being ahead of ~ N1
に[先駆「さきが」]けて => The earliest, very first in A; Ahead of A, in advance of A N1
Time, Situation