  Synthesis of highly $^{13}$C isotope enriched azafullerene, C$_{59}$N
embedded in C$_{60}$ is reported. $^{13}$C enriched fullerenes, produced with
the Kr\"{a}tschmer-Huffmann process, were subject to a N$_{2}$ discharge that
produces C$_{59}$N with a low probability. Raman spectroscopy indicates a
homogeneous $^{13}$C distribution. Electron spin resonance measurement (ESR)
proves that the C$_{59}$N concentration, 0.2 %, is similar as in non-enriched
fullerenes. The ESR spectrum is simulated accurately with the known $^{14}$N
and $^{13}$C hyperfine coupling constants. The material enables the nuclear
spin-labelling of heterofullerene complexes with a potential for biological
applications. It might also find applications as a building element for quantum
computation.
