Crystal and molecular structure of N-(1-ethoxycarbonyl-ethyl) 1-ethoxycarbonylmethyl-3-ethyl-1,2,3,4-tetrahydro-4-oxo-1,3,2-benzodiazaphosphorin-2-carboxamide 2-oxide

The crystal structure of the title compound N-(1-ethoxycarbonyl-ethyl) 1-et hoxycarbonylmethy-3-ethyl-1,2,3,4-tetrahydro-4-oxo-1,3,2-benzodiazaphosphor in-2-carbox amide 2-oxide, (C19H26N3O7P, M-r = 439.41), was determined by s ingle crystal X-ray diffraction at 299(1) K. It crystallizes in the triclin ic system, space group P (1) over bar (No.2) with a = 8.955(2), b=11.863(2) , c = 12.309(2) Angstrom, a = 62,67(3), beta = 68.10(3), gamma = 78.07(3)de grees, V = 1077(1) Angstrom (3), Z = 2, D-x =1.355 g.cm(-3), lambda = 0.710 73 Angstrom, mu = 0.1657 mm(-1) and F(000) = 464. The structure was solved by direct methods. The final R factor is 0.071 and Rw is 0.076 for 2176 obs erved reflections with I greater than or equal to3 sigma (I). The results f rom X-ray crystallography analysis of the isomer with P-31 NMR spectra exhi bited as delta 4.09 show that the absolute configuration of the chiral phos phorus atom at P(1) was proved to be S-form, with reference to the known co nfiguration of R-alanine moiety.