MicroED structure determination · Industry updates · Page 4
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MICROED / 3D ELECTRON DIFFRACTION
Pharmaceutical structures and polymorphs: the literature library
Explore significant papers from 2018 onward by year, author, DOI, and application. Historical papers retain their original publication dates.
Researchers determined the structures of five vemurafenib polymorphs directly from compact spherulites using 3D electron diffraction. Three matched known single-crystal X-ray structures, while the method resolved a difficult delta form and a newly observed epsilon form. The work expands access to melt-grown polymorphs whose morphology or instability can frustrate conventional single-crystal analysis.
MicroED determined a powder-derived cocrystal of 2-aminopyrimidine and succinic acid prepared by solid-state grinding. The mechanically generated phase was not accessible through the solution-crystallization route examined. This is a model organic cocrystal rather than an API efficacy study, illustrating how electron diffraction can characterize crystal-engineering products without first recreating them as large solution-grown crystals.
Researchers analyzed micron-sized powders of SMTP-7 and its diastereomer to resolve stereochemical assignments. Kinematical refinement combined with additional chiral information and dynamical refinement provided complementary routes. The work demonstrates absolute-configuration analysis for complex, hard-to-crystallize drug candidates with limited material, while distinguishing what can be inferred from conventional refinement and what requires dynamical treatment.
This review examines three-dimensional electron diffraction for beam-sensitive small-molecule nanocrystals, with a pharmaceutical-industry perspective. It discusses experimental strategies, diffraction completeness, dynamical scattering, and structural applications that extend beyond conventional large-crystal requirements. It provides a methods-oriented framework for interpreting published demonstrations; it does not establish a universal preparation method or replace sample-specific feasibility assessment.
Three-dimensional electron diffraction and scanning transmission electron microscopy resolved the layered structure and stacking variations of bismuth subsalicylate, a long-used pharmaceutical ingredient. Clustering compatible diffraction datasets helped obtain the ordered structural model, while imaging exposed disorder. The paper shows why complementary electron-crystallography techniques can be valuable when small crystals and structural defects obstruct conventional characterization.
The authors determined the absolute configuration of a preclinical API by forming a salt with a chiral reference and analyzing its microcrystalline powder using MicroED. This approach transfers known stereochemical information from the salt former to the API. It addresses situations where large crystals cannot be obtained, but depends on a suitable, well-characterized chiral reference.
Three-dimensional electron diffraction showed that solution-grown and melt-grown materials previously grouped as delta-indomethacin have different crystal structures. The authors retained delta for the solution-grown form and proposed theta for the melt-grown form. Both displayed plastic bending associated with molecular slip. This case demonstrates how structural measurements can resolve longstanding ambiguity in polymorph identity.
Researchers solved a previously unresolved indomethacin form by three-dimensional electron diffraction and related its packing to infrared and Raman observations. They measured faster dissolution than the better-characterized alpha and gamma forms and observed a solid-state transition to alpha. This is a solid-form structure–property study; laboratory dissolution results do not by themselves establish improved human bioavailability.
Researchers described a pharmaceutical MicroED service workflow after examining more than fifty client-submitted small-molecule samples. Most yielded diffraction data suitable for structure solution, and validation examples included common reference compounds and teniposide. The paper documents preparation, collection, processing, and typical obstacles; its selected service cohort does not establish a universal success rate.
This review introduces the development and scope of MicroED, from small molecules and peptides to proteins and larger complexes. It explains how nanocrystalline samples extend crystallographic opportunities and summarizes the method’s trajectory. Its value for pharmaceutical materials is conceptual orientation; readers should use dedicated API studies to evaluate solid-form identification and industrial performance.
This study combined MicroED with crystal structure prediction to support solid-form selection for remdesivir. Experimentally determined structural information was evaluated alongside computational crystal-energy analysis, demonstrating a joint experimental and modeling approach when conventional large-crystal growth is difficult. The work concerns solid-state characterization and selection, not a new assessment of antiviral efficacy or clinical performance.
MicroED analysis of lomaiviticin C prompted revision of its molecular connectivity and stereochemical assignments. High-field NMR and computational analysis supported the revised interpretation, with implications for related lomaiviticins. This is a natural-product structure-elucidation landmark rather than a pharmaceutical-polymorph study, demonstrating the value of complementary methods when complex, sparsely protonated molecules resist confident NMR assignment.
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