Synthesis and structure of N-ferrocenoyl-labeled tripeptide: N-Fc-L-Pro-L-Leu-Gly-OMe

The synthesis, characterization and crystal structure of the title compound, N-ferrocenoyl-L-Pro-L-Leu-Gly-OMe (Fc-PLG), were reported in this paper. The title compound crystallized in a monoclinic system, space group C2 with Z = 4, a = 20.803(3) Å, b = 6.4428(4) Å, c = 20.557(2) Å, α = 90°, β = 115.498(5)°, γ = 90°; R = 0.0451. The Cp rings in the ferrocenoyl group are nearly coplanar, making a dihedral angle of 178.2 (4)°, while the substituted cyclopentadienyl ring and the proline ring are virtually coplanar with a very small twist angle of 14.0°. Strong hydrogen bonds between the Gly amide group N13 and the Pro carbonyl group O11 (d (N … O) = 2.835 Å) make the molecules fold into a β-turn conformation.