Shota Yoshioka

X-ray analysis on the nanogram to microgram scale using porous complexes

X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram–microgram order. We demonstrate that as little as about 80 nanograms of a sample is enough for the SCD analysis. In combination with high-performance liquid chromatography, our protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liquid chromatography SCD analysis. Furthermore, we unambiguously determined the structure of a scarce marine natural product using only 5 micrograms of the compound.

Where is the Oxygen? Structural Analysis of α‐Humulene Oxidation Products by the Crystalline Sponge Method

Crystal structures of α-humulene, a cyclic sesquiterpene, and its oxidized subproducts, were analyzed by the crystalline sponge method. Regio- and stereochemistry, including absolute configuration when a chiral oxidant was applied, and the stable conformations of all the scaffold-related compounds were successfully determined for samples on a 5-50 μg scale.

Corrigendum: X-ray analysis on the nanogram to microgram scale using porous complexes

This corrects the article DOI: 10.1038/nature11990

X-ray Structure Analysis of Ozonides by the Crystalline Sponge Method.

The crystalline sponge method was used for the X-ray structure analysis of ozonide compounds. As this new technique requires only microgram quantities of the samples, structural analysis can be conducted without product isolation, isomer separation, or crystallization and most importantly without any risk of explosion.

Finding a New Crystalline Sponge from a Crystallographic Database

Empirical searching conditions were adopted to identify suitable candidates from the Cambridge Structural Database (CSD) for crystalline sponge hosts for X-ray crystallographic analysis of incoming guest compounds. After optimization of the solvent and soaking conditions, one of the candidates was used as a crystalline sponge for the structure determination of an aromatic guest.

Oligoacetylacetones as shapable carbon chains and their transformation to oligoimines for construction of metal-organic architectures

Flexible chain-like molecules can adopt various conformations, but fabrication of complex and higher-order architectures by chain networking or coiling is still a difficult task in organic chemistry. As the degree of freedom increases, the large entropy loss impedes conformation and orientation fixing. Here we report oligo (3,3-dimethylpentane-2,4-dione)s as flexible and shapable carbon chains with many carbonyl groups for chemical modification. Polycarbonylated chains of various lengths are synthesized by terminal-selective silylation and oxidative coupling reactions using silver(I) oxide. We use reactions of 1,3-diketones and 1,4-diketones to reduce the chain length and to induce favourable conformations. When the chains are treated with hydrazine, all the carbonyl groups are converted to imine groups, resulting in the formation of multidentate ligands. Finally, a two-dimensional sheet-like structure and a cylindrical assembly are generated by respectively networking and coiling the carbon chains, with the aid of metal coordination.Constructing metal-organic architectures with flexible organic linkers is challenging as there is an entropic barrier to their adopting well-defined conformations. Here the authors use oligoketones as precursors to flexible oligoimine linkers for two-dimensional and three-dimensional metal-organic assemblies.