¹⁵N, ¹³C, or both isotope labels were introduced in selected positions of several LCPAs containing 5, 11, or 13 nitrogens. The number of transformations during chemical synthesis was minimized by coupling Fmoc-glycine-¹⁵N, Fmoc-glycine-1-¹³C, or Fmoc-β-alanine simultaneously at both ends of the growing oligoamide chain on resin-linked norspermidine. LCPAs containing 10–20 nitrogens are the main organic constituent of diatom biosilica. Preliminary NMR studies of bioinspired silica nanocomposites obtained from double-labeled LCPA 14 and ²⁹Si-enriched orthosilicic acid identified the close spatial arrangement of ²⁹Si and ¹³C nuclei.