We succeeded in the first isolation of a single pure regioisomer of a C-70-acene monoadduct. 1,9-Diels-Alder monoadducts of C-70 with pentacene derivatives were obtained by not only the Diels-Alder reaction but also a one-pot reaction using stable dihydropentacene derivatives, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and C-70. The X-ray crystallographic study of a single pure regioisomer 2b confirmed positions of the linkage between C-70 and acenes for the first time, and revealed unique columnar stacks.