Pseudomerohedrally twinned monoclinic structure of unfolded `free' nonactin: comparative analysis of its large conformational change upon encapsulation of alkali metal ions

Abstract

The title compound, C 40 H 64 O 12 , crystallizes in a pseudomerohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-molecules of nonactin in the asymmetric unit. Each molecule has a pseudo-S 4 symmetry and resides on a crystallographic twofold axis; the axes pass through the molecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nonactin as an order-disorder structure in an orthorhombic unit cell is corrected. We report a low-temperature high-precision ordered structure of 'free' nonactin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na + , K + , Cs + , Ca 2+ or NH 4 + cations that exhibit more isometric overall conformations.

Strain Streptomyces sp. P-56 Produces Nonactin and Possesses Insecticidal, Acaricidal, Antimicrobial and Plant Growth-Promoting Traits

“…Obtaining high-quality nonactin crystals and their X-ray diffraction analysis are associated with certain difficulties, which were previously described in detail [ 54 ]. In particular, nonactin crystals without metal ions have a primitive monoclinic cell with twinning.…”

Isolated alkali cation complexes of the antibiotic ionophore nonactin: correlation with crystalline structures

“…Some of the simulated annealing runs were seeded with initial conformations built from the crystallographic data available for the systems. [41][42][43][44] All trial structures were computed with each of the three cations as a guest. Altogether, about twenty non-redundant structures of each of the complexes were optimized at the B3LYP/6-311+G(d) level.…”

Two polymorphs of chlorido(cyclohexyldiphenylphosphine)gold(I)

“…The structure of (It) was pseudo-merohedrally twinned, likely due to the proximity of the angle to 120 and similarity of the a and c axial lengths. We have recently reported a case of a nonmerohedrally twinned crystal of nonactin (Guzei et al, 2009) and treated the twinning in (It) according to the procedure described therein. In the case of (It) the twin law (101 0 " 1 10 00 " 1 1) corresponded to a 180 rotation about the a* axis in reciprocal space.…”