The novel, functionalized heteropolymolybdates [RPMo6O21(O2CCH2NH3)(3)](2-) (R = OH, CH3, C2H5, H) have been synthesized and characterized by IR, P-31 NMR spectroscopy, and elemental analysis. Single-crystal X-ray analysis was carried out on K-2[HOPMo6O21(O2CCH2NH3)(3)].8.5H(2)O, which crystallizes in the orthorhombic system, space group Pnma, with a = 14.118(2) Angstrom, b = 20.660(3) Angstrom, c = 12.191(2) Angstrom, and Z = 4; K-2[H3CPMo6O21-(O2CCH2NH3)(3)].8.5H(2)O, which crystallizes in the orthorhombic system, space group Pnma, with a = 14.1643(6) Angstrom, b = 20.8658(8) Angstrom, c = 12.2235(5) Angstrom, and Z = 4; and K-2[HPMo6O21(O2CCH2NH3)(3)]-8H(2)O, which crystallizes in the orthorhombic system, space group Pnma, with a = 14.092(3) Angstrom, b = 20.696(2) Angstrom, c = 12.199(4) Angstrom, and Z = 4. We also report on the synthesis and characterization of the isostructural derivative K-2[H5C2PMo6O21(O2CCH2NH3)(3)]. The four title polyanions consist of an RP (R = OH, CH3, C2H5, H) hetero group surrounded by a ring of Six MoO6 octahedra sharing edges and corners alternatingly. Three glycine molecules are each bound to two edge-sharing Mo centers via their carboxylate functionality on the same side of the ring. The central phosphorus atom is located slightly above the plane of the six molybdenums, and its terminal R group is on the same side of the ring as the glycines. NMR studies show that the solid state structures of the title compounds are preserved in solution.