The present invention relates to the compound of formula (1a) wherein p is 1 or 2, R1-R4 are hydrogen atom or the like, and a-d are 1 or 2, or a pharmaceutically acceptable salt thereof, which has an antitumor effect by inhibiting the binding between a MLL fusion protein that is infused with AF4, AF9, or the like, which is a representative fusion partner gene causing MLL leukemia, and menin.