I. Development of an Isoxylitone Analog as an Anti-epileptic Drug Candidate; II. Synthesis of SOX9 Inhibitors as Promoters of Recovery from Spinal Cord Injury.
Creators: name: Haeck, Julien
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2023
Subjects: Epilepsy
Spinal Cord Injury
Medicinal chemistry

description: Part I. Development of an isoxylitone analog as an antiepileptic drug candidate. Delphinium denudatum is a medicinal plant traditionally used to treat a variety of conditions in Central Asia. Its interesting anticonvulsant effects were determined to be a property of the compound isoxylitone. Prior work from our group in collaboration with the Poulter group from Western University investigated this compound and generated a large number of isoxylitone analogs in order to optimize its antiepileptic activity. This led to the discovery of the prodrug 13 and the active form 15 shown below, which emerged as the most potent. In this work, the library of analogs was further expanded with 22 new compounds with several which matched the activity of 13 and 15, such as compounds 22 and 37, which led to valuable new insights on the activity of these analogs, and suggested other possible future improvements. In addition, efforts were continued regarding developing compound 15 as a clinical trial candidate. Optimization of the synthesis was performed to drastically reduce costs and waste of chemicals, as well as accelerating the duration of the synthesis. The purification of the final product was also greatly facilitated by the direct synthesis of 15, compared to the prior process of first preparing 13 and hydrolyzing the ester. Efforts were exerted to gather additional knowledge on the characteristics of the compound, with structural and conformational analysis via X-ray crystallography and NOE NMR as well as accelerated stability studies to test the viability of 15 in long-term storage under various conditions. All the information gathered throughout this work supported 15 and its sodium salt as excellent clinical trial candidates as treatments for epilepsy. Part II. Synthesis of SOX9 inhibitors as promoters of recovery from spinal cord injury. According to the World Health Organization, 250 to 500 thousand people develop a spinal cord injury each year with a large portion resulting in tetraplegia. A common misconception is that this is permanent because the damaged nerves cannot be repaired. In fact, nerves can and do regrow after being damaged, but cannot do so after spinal cord injuries due to formation of scar tissues which physically and chemically prevents the healing. The Brown group at Western University identified the SOX9 transcription factor as an important promoter of the formation of this scar and showed that SOX9 inhibitors could improve recovery and mobility in mice affected by spinal cord injuries. In collaboration with their group, previous work in our lab performed and SAR study on the lead compounds ZO2(1) and STL26 (2), shown below. The different sections of the molecule have been designated units A to D, to simplify discussion. Initial work by our group established an efficient method to prepare a library of analogs of the lead compounds. A number of compounds were prepared, which primarily investigated small amines as unit A and phenols with small aliphatic substituents as unit D. The initial SAR data confirmed the validity of STL26 as lead compound, as most alterations to the structure were detrimental to the SOX9 inhibitory activity. The objective of this work was to build on these preliminary SAR results, and expand the library of analogs. Larger substituents were introduced in unit A and D and showed that any group larger or smaller than diethylamide in unit A was detrimental to the activity, but that there seemed to be ample space to increase the size of the unit D isopropyl group. Analogs investigating unit B showed that adding substituents at most of the positions was detrimental, as well as changing the relative positions of unit A and B to be ortho or para to each other. However, the C4 on ring B seemed to be very tolerant to various electron donating or withdrawing functional groups. During this SAR study, a recurring theme was the awful solubility of the compounds in water, which heavily complicated their administration to mice during the bioassays. While none of the analogs tested proved superior to 2, the knowledge accrued during this work painted a clear path forward on which areas of the structure could be safely altered to improve solubility without negative impacts on SOX9 inhibition. Some additional efforts were put into obtaining an accurate three-dimensional structure of an active STL26 (2) analog, and information on the primary conformation in solution. Achieving these goals required the use of NOE NMR experiments and X-ray crystallography. One conformation was discovered to be strongly favoured as a result of an intramolecular hydrogen bond even in protic solvents. Subsequently, a small number of additional analogs were prepared containing modifications that would strongly favor or hinder the preferred conformation, in order to better understand its role in the inhibitory activity. The presence of this hydrogen bond appeared to be key to the activity of the compounds.