Determination of the absolute configuration of compounds bearing chiral quaternary carbon centers using the crystalline sponge method

Abstract

The absolute configuration of organic compounds bearing chiral quaternary carbons is determined by the crystalline sponge method.

The growing importance of crystalline molecular flasks and the crystalline sponge method

“…2). 13 The method was practically applied to revise the absolute structure of a pair of natural products, cycloelatanene A and B, which were isolable only as oils in trace quantities. 14 Initial structural reports 15 made using COSY, HMBC and NOE NMR analyses had misassigned a single stereocentre of the spiro [5.5]undecene scaffold, which was later clearly visualised by the crystalline sponge method.…”

Stepwise Evolution of Molecular Nanoaggregates Inside the Pores of a Highly Flexible Metal–Organic Framework

“…[17] In the CSM, the analyte molecule is adsorbed inside the MOF pores,w hich provide al ong-range-ordered environment to the guest, making possible its structural determination via SCXRD. [18,19] This method relies on the frameworks robustness,w hich generally preserves the single-crystallinity even after significant guest loading. [20,21] Framework adaptability to guest uptake and stimuli responsiveness behavior are two of the most intriguing feature of the so-called breathing MOFs.…”

“…[27][28][29] However,i ns everal cases,t he determination of the guest species remains av ery demanding task [4] owing to the weak host-guest intermolecular interactions,mainly H-bonds, halogen-bonds,o rp-p interactions very often characterized by as ignificant positional disorder, [30] large thermal motion, and low occupancy. [4] Even though several works focusing on CSM have been presented so far, [18,19,[31][32][33] the analysis of the guest entering dynamics has not been explicitly investigated, [21,34,35] nor the formation of nanoconfined aggregates of the trapped molecules. [36,37] Recent works have shown that cutting-edge use of SCXRD allows the elucidation of inclusion processes occurring inside MOF cavities based on structural insight.…”

Stepwise Evolution of Molecular Nanoaggregates Inside the Pores of a Highly Flexible Metal–Organic Framework

“…MOFs have been largely studied as functional materials for gas separation and storage, and more recently as crystalline host, after work by Fujita on the crystalline sponge method (CSM) . In the CSM, the analyte molecule is adsorbed inside the MOF pores, which provide a long‐range‐ordered environment to the guest, making possible its structural determination via SCXRD . This method relies on the frameworks robustness, which generally preserves the single‐crystallinity even after significant guest loading .…”

“…However, in several cases, the determination of the guest species remains a very demanding task owing to the weak host–guest intermolecular interactions, mainly H‐bonds, halogen‐bonds, or π–π interactions very often characterized by a significant positional disorder, large thermal motion, and low occupancy . Even though several works focusing on CSM have been presented so far, the analysis of the guest entering dynamics has not been explicitly investigated, nor the formation of nanoconfined aggregates of the trapped molecules …”