  We investigate nuclear spin hyperpolarization from nitrogen vacancy centers
in isotopically enriched diamonds with $^{13}$C concentrations up to 100%.
$^{13}$C enrichment leads to hyperfine structure of the nitrogen vacancy
electron spin resonance spectrum and as a result the spectrum of dynamic
nuclear polarization. We show that strongly-coupled $^{13}$C spins in the first
shell surrounding a nitrogen vacancy center generate resolved hyperfine
splittings, but do not act as an intermediary in the transfer of
hyperpolarization of bulk nuclear spins. High levels of $^{13}$C enrichment are
desirable to increase the efficiency of hyperpolarizaiton for magnetic
resonance signal enhancement, imaging contrast agents, and as a platform for
quantum sensing and many-body physics.
