0000000000704310
AUTHOR
Liliana Mazur
Molecular and crystal structure of Nα-(9-fluorenyl)-methoxycarbonyl-L-ornithine hydrochloride diethyl ether solvate
The solid-state conformation of the first N-protected ornithine derivative has been established by X-ray analysis. The hydrochloride of Nα-(9-fluorenyl)methoxycarbonyl-l-ornithine crystallises as diethyl ether solvate. The backbone (ω0 ϕ, ψ χ1) torsion angles are (174.9°,–84.0°, 145.9°,–171.0°). The conformation of the urethane amide bonds istrans. The ornithine aliphatic side chain adopts preferred fully extended conformation which is stabilised by the hydrogen bonding of the-NH3+ group to the diethyl ether molecule, carboxyl group and Cl− anions.
Geometrical and conformational preferences of the 9‐fluorenylmethoxycarbonyl‐amino moiety
Structural parameters, originating from x-ray crystallographic data, have been compiled for 13 derivatives of amino acids, peptides and related compounds, which contain a total of 14 Fmoc-NH- moieties. For these moieties, molecular geometries and conformations--described by the omegao, theta1, theta2 and theta3' torsion angles--were analysed and compared with the corresponding parameters for the Z-NH- and Boc-NH-moieties (290 and 553, respectively). To gain a deeper insight into the conformational features of the Fmoc-NH- moiety, ab initio free molecule calculations were performed for fully relaxed minima. Also the potential energy surface as a function of the torsion angles (theta3', theta…