Structure and conformation of peptides: N ‐benzyloxycarboyl‐(γ‐ethyl)‐ L ‐glutamyl‐(γ‐ethyl)‐ L ‐glutamic acid ethyl ester

C 24 H 34 N 2 O 9 , orthorhombic, P2 1 2 1 2 1 ; a = 39.432 (10), b = 14.061 (5), c = 4.850 (2) Å, M = 494 a.m.u., Z = 4, Dm = 1.22 g cm −3 , Dx = 1.22 g cm −3 , R = 0.13 for 1205 observed reflections after refinement with isotropic thermal factors. The urethane and amide bonds are in the trans configuration, as well as all the ester groups. The φ and ψ angles of the L ‐glutamyl residues fall in the β‐structure region of the Ramachandran's plot; the molecule is rather flat with the amide plane almost parallel to the c axis along which two hydrogen bonds hold the molecules together to form long rows in a “parallel pleated‐sheet” fashion.