摘要:
                                Helicopodands are a new class of chiral nonmacrocyclic ("podand") receptors with a helicene backbone ("helico").  At the termini of the helix, they form a preorganized cleft of pronounced asymmetric character which is aligned with convergent hydrogen bonding functionality.  The synthetic routes to the two helicopodands 2 and 3 each include two photocyclodehydrogenation reactions.  The X-ray crystal structure of 14, a direct helical precursor to 2 and 3, confirms the main structural features of the helicopodands.  MMP2 calculations give a geometric description of 14 which is in reasonable agreement with the X-ray results.