Advisor(s)

Alexandros Makriyannis

Contributor(s)

David Janero, Robert Hanson, Spyros Nikas, Andreas Goutopoulos

Date of Award

2012

Date Accepted

3-2012

Degree Grantor

Northeastern University

Degree Level

Ph.D.

Degree Name

Doctor of Philosophy

Department or Academic Unit

Bouve College of Health Sciences, Department of Pharmaceutical Science

Keywords

pharmaceutical sciences, organic chemistry, chemistry, anandamide, cannabidiol, cannabinoid, covalent probes, SAR, THC

Disciplines

Medicinal and Pharmaceutical Chemistry | Natural Products Chemistry and Pharmacognosy | Pharmacy and Pharmaceutical Sciences

Abstract

Part I

Delta-9-tetrahydrocannabinol (THC) and (-)-cannabidiol (CBD) are the major constituents of Cannabis sativa (marijuana). (-)-CBD shares many of delta-9-THC's therapeutic properties without inducing negative psychotropic effects. These include potential medicinal uses for anti-inflammation, neuroprotection, anxiolytic, anti-nausea and anti-cancer that are all of great therapeutic importance. The clinical potential of (-)-CBD has been realized with the recent approval of Sativex® in Canada, a drug consisting of a 1:1 mixture of delta-9-THC and (-)-CBD for relief of neuropathic and cancer-related pain. Nonetheless, the levorotatory (-)-CBD natural product binds with low affinity to the two principal cannabinoid (CB) G protein-coupled receptors, CB1R and CB2R, whereas the synthetic dextrorotatory (+)-CBD enantiomer binds to both with high (nanomolar) affinity. However, little is known regarding (+)-CBD ligand-binding and functional domains at these receptors, and structure-activity relationship (SAR) data around (+)-CBD is sparse. In this dissertation, a number of high-affinity (+)-CBD analogs have been synthesized in order to explore the SAR. The SAR focused on the side-chain, northern-end, and phenolic hydroxyl pharmacophores of the (+)-CBD prototype. In vitro leads were selected based on their high binding affinity, selectivity as CB2R agonists or CB1R partial agonists, drug-like physicochemical properties, and modulation of in vitro pharmacological activity (cAMP, beta-arrestin assays). These leads were profiled in a panel of rodent paradigms for in vivo cannabinergic activity (hypothermia, catalepsy and tail-flick tests). AM9200 was demonstrated to have a longer duration of action as compared to its metabolite, AM9201, whereas (+)-CBD analogs AM9217 and AM9248 were (weak) partial agonists active in vivo. AM9252 and AM 9222 showed potent analgesic and hypothermic effects in mice and rats, suggesting agonist activity at both CB1R and CB2R. AM 9252 was also shown to have analgesic effects comparable to synthetic delta-9-THC analog (AM 4054) in non-human primates. Also, in order to obtain structural information regarding the binding site of (+)-CBD analogs with these membrane-bound proteins, pharmacologically active (+)-CBD analogs designed as covalent probes to wild-type and mutant CB1R and CB2R are being profiled to help characterize their binding site(s).

Part II

Anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) are the two key endocannabinoids that act at CB1R and CB2R to modulate physiological and pathological processes including nociception, inflammation, neuroprotection, feeding behavior, anxiety, memory, and cell proliferation. They are produced "on demand," are rapidly inactivated by enzymatic hydrolysis, and serve as substrates for oxidative metabolism by cyclooxygenases and lipoxygenases, making it difficult to study directly their in vivo physiology and pharmacology. For the development of novel endocannabinoid templates with potential resistance to hydrolytic and oxidative metabolism, we targeted the methylation of the bis-allylic carbons of the arachidonoyl skeleton. Towards this end, the synthesis and preliminary biological data for the (13S)-methyl-anandamide analog were recently disclosed from our laboratory. This compound was found to have the highest CB1 binding affinity among anandamide analogs to date. Based on this discovery, this dissertation reports the total synthesis of the (10S)- and (10R)-methyl-counterparts. The synthetic approach used was stereospecific, efficient, and provided the chiral analogs without the need for resolution. Biological testing showed that (10S)- and (10R)-methyl anandamide analogs bound to CB1 and CB2 with moderate affinity.

To explore the binding motifs of the novel (13S)-methyl-substituted arachidonoyl template, the respective tail-modified covalent probes (at C-20) were synthesized and profiled. The covalent probes bound to the CB1R and CB2R with low nanomolar affinity and are currently being tested for their ability to covalently label the CB receptors.

Document Type

Dissertation

Rights Information

copyright 2012

Rights Holder

Marsha Rebecca D’Souza


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