X-ray diffraction experiments have evidenced that the orientation of t
he aromatic side chain determine the folding tendencies of (BuCO)-Bu-t
-Pro-c(6)Phe-(NHPr)-Pr-i, where c(6)Phe denotes the (S,S) and (R,R) cy
clohexane analogues of phenylalanine. In the solid state, both dipepti
des are beta-folded, the beta-turn type being dictated by the stereoch
emistry of the cyclohexane ring. (C) 1998 Published by Elsevier Scienc
e Ltd. All rights reserved.