Structure of a Hydrated Sodium-Lasalocid A (X-537A) Dimer: An Intermediate in Complex Formation

A sodium-lasalocid A-water (2:2:2) complex, crystallized from 95% ethanol, appears to be an intermediate in the monomer to dimer transition that accompanies ion capture and transport. The complex crystallizes in the monoclinic space group P2i with cell dimensions a = 12.148 (2) Å, b = 27.589 (3) Å, c = 11.802 (3) Å, β = 110.25 (1)°, and Z = 2. The structure consists of two sodium ions and two water molecules enclosed by two lasalocid A ions. Six of the seven oxygens coordinated to one sodium ion are contributed by both lasalocid A ions; a water molecule provides the seventh site. The other sodium ion is coordinated to four oxygens of a single lasalocid A ion and both water molecules.