The 293 K structure of tetradehydrohaliclonacyclamine A.

The polycyclic title compound {systematic name: (1S,16S,17S,31S)-3,20-diazatetracyclo[15.15.0(1,17).1(3,31).1(16,20)]tetratriaconta-6,8,23,25-tetraene}, C(32)H(52)N(2), has recently been isolated and characterized structurally, in solution by NMR spectroscopy and in the solid state by X-ray crystallography. At 130 K the structure is monoclinic (P2(1), Z = 4) and comprises two molecules in the asymmetric unit with distinctly different conformations in the twelve-C-atom bridging chains. We report that, at 250 K, a phase change from monoclinic to orthorhombic (P22(1)2(1), Z = 4) occurs. The higher-temperature phase is structurally characterized herein at 293 K. The two different conformers resolved in the monoclinic low-temperature form merge to give a single disordered molecule in the asymmetric unit of the high-temperature phase.