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Introduction NCBME, C21H32NO.Br, crystallizes in the orthorhombic space group P2~2~21 with a = 11.379 (1), b = 15.314 (1), c = 11.657 (1) A and Z = 4. The structure was solved from a Patterson synthesis and refined to R = 0.036 for 1808 independent reflections. NME, C17HE6NO.Br.2H20, has orthorhombic symmetry, P2~2~2~, with a = 7.146 (1), b = 12.867 (1), c = 19.899 (1)/~ and Z = 4. The structure was solved from a Patterson synthesis and refined to R = 0.039 for 1561 independent reflections. The absolute configuration of the two compounds was determined by coordinate inversion. Hydrogen bonds between Br, O and N atoms link the molecules in the crystal. In NME an extensive network of hydrogen bonds is built up by the presence of the two water molecules.

Structure determination and refinementThe phase problem was solved by SIMPEL (Schenk, Overbeek & van der Putten, 1976). Refinement was by block-diagonal least squares. Towards the end of the anisotropic refinement a difference synthesis revealed the H atoms which were included with isotropic temperature parameters. A weighting scheme w =