Different intra- and inter-molecular hydrogen-bonding patterns in (3,4a,8a)-2-[(2,3)-3-(2,5--benzamido)-2-(2,5--benzo-yloxy)-4-phenyl-butyl]---butyldeca-hydro-iso-quinoline-3-carboxamides ( = H or Cl): compounds with moderate aspartyl protease inhibition activity.

The crystal structures of (3,4a,8a)-2-[(2,3)-3-benzamido-2-benzo-yloxy-4-phenyl-but-yl]---butyldeca-hydro-iso-quinoline-3-carboxamide, CHNO, (I), and (3,4a,8a)-2-[(2,3)-3-(2,5-di-chloro-benzamido)-2-(2,5-di-chloro-benzo-yloxy)-4-phenyl-but-yl]---butyldeca-hydro-iso-quinoline-3-carboxamide, CHClNO, (II), are described. Despite their chemical similarity, they adopt different conformations in the solid state: (I) features a bifurcated intra-molecular N-H⋯(N,O) hydrogen bond from the -butylamide NH group to the piperidine N atom and the benzoate O atom, whereas (II) has an intra-molecular N-H⋯O link from the benzamide NH group to the -butyl-amide O atom. In the crystal of (I), mol-ecules are linked by (4) amide N-H⋯O hydrogen bonds into chains propagating in the [010] direction, with both donor and acceptor parts of the benzamide group. In the extended structure of (II), (11) N-H⋯O chains propagating in the [010] direction arise, with the donor being the -butylamide NH group and the acceptor being the O atom of the benzamide group.