1
|
Lerdwiriyanupap T, Belletti G, Tinnemans P, Cedeno R, Meekes H, Vlieg E, Flood AE. Influence of Ostwald's Rule of Stages in the Deracemization of a Compound Using a Racemic Resolving Agent. CRYSTAL GROWTH & DESIGN 2022; 22:1459-1466. [PMID: 35140550 PMCID: PMC8815034 DOI: 10.1021/acs.cgd.1c01426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/14/2022] [Indexed: 06/14/2023]
Abstract
The stereoisomeric system of rac-2-phenylglycinamide (PGA) and rac-N-acetyl tryptophan (NAT) is significant in the application of chiral resolution because it has been shown that this system can be used for enantioseparation of PGA and/or NAT using a novel deracemization route of the conglomerate salt formed. However, it was also found that the conglomerate salt eventually converted into different crystal forms that limited the time available for the separation. Herein, we try to understand the phase conversion occurring in this system using DSC, PXRD, and SC-XRD. The related structures of the salt (two polymorphs of the more stable homochiral (dd- and ll-) salts and one polymorph of the less stable heterochiral (dl- and ld-) monohydrate salts) are demonstrated and discussed relating to their relative stabilities. The successful deracemization was demonstrated using the heterochiral (dl- or ld-) monohydrate salts. However, following Ostwald's rule of stages, only limited time is available for the deracemization before the metastable compound converts into the more stable homochiral (dd- and ll-) pair. Moreover, the occurrence of the (dd- and ll-) phase always coincides with the formation of yet another phase of the racemic compound containing four components in a crystal. Ostwald's rule of stages here thus involves three steps and phases and is highly significant during the deracemization of the homochiral species.
Collapse
Affiliation(s)
- Tharit Lerdwiriyanupap
- Department
of Materials Science and Engineering, School of Molecular Science
and Engineering, Vidyasirimedhi Institute
of Science and Technology, Rayong 21210, Thailand
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Giuseppe Belletti
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Paul Tinnemans
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Ruel Cedeno
- Department
of Chemical and Biomolecular Engineering, School of Energy Science
and Engineering, Vidyasirimedhi Institute
of Science and Technology, Rayong 21210, Thailand
| | - Hugo Meekes
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Elias Vlieg
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Adrian E. Flood
- Department
of Chemical and Biomolecular Engineering, School of Energy Science
and Engineering, Vidyasirimedhi Institute
of Science and Technology, Rayong 21210, Thailand
| |
Collapse
|