Structure of tBuCO-Gly-Gly psi [CH2-N+H2]NHEt.BPh4-

N-(tert-Butylcarbonylglycylaminoethyl)-N-(ethyl)ammonium tetraphenylborate, C11H24N3O+2.C24H20B-, Mr = 549.57, triclinic, P-1, a = 11.567 (2), b = 11.922 (2), c = 14.484 (3) A, alpha = 70.99 (2), beta = 74.83 (2), gamma = 59.33 (1) degrees, V = 1613.1 A3, Z = 2, D chi = 1.13 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 4.69 cm-1, mu Rmax much less than 1, F(000) = 592, T = 293 K, R = 0.058 for 3491 observed reflections. This pseudopeptide is folded by a short N(+)-H ... O = C hydrogen bond (N3 ... O1 = 2.81 A) which closes a ten-membered ring. This results in a beta-turn structure that can be classified as type II on the basis of the conformational angles for the N-terminal glycine. The conformational angles phi 1, psi 1, phi 2 and psi 2 are -53.4 (6), 139.7 (4), 91.5 (5) and -62.6 (6) degrees respectively.