The Diels-Alder Approach towards Cannabinoid Derivatives and Formal Synthesis of Tetrahydrocannabinol (THC)

Based on the Diels-Alder reaction of vinylchromenes with electron-poor dienophiles, we developed a strategy for the synthesis of tetrahydrocannabinol derivatives. Substituted vinyl chromenes could be converted with several dienophiles to successfully isolate several complex molecules. These molecules already contain the cannabinoid-like base structure and further processing of one such derivative led to a precursor of Delta(9)-tetrahydrocannabinol. The most challenging step towards this precursor was an epoxidation step that was ultimately achieved via dimethyl dioxirane.Peer reviewe

Targeting oxidative stress: Novel coumarin-based inverse agonists of GPR55

Oxidative stress is associated with different neurological and psychiatric diseases. Therefore, development of new pharmaceuticals targeting oxidative dysregulation might be a promising approach to treat these diseases. The G-protein coupled receptor 55 (GPR55) is broadly expressed in central nervous tissues and cells and is involved in the regulation of inflammatory and oxidative cell homeostasis. We have recently shown that coumarin-based compounds enfold inverse agonistic activities at GPR55 resulting in the inhibition of prostaglandin E2. However, the antioxidative effects mediated by GPR55 were not evaluated yet. Therefore, we investigated the antioxidative effects of two novel synthesized coumarin-based compounds, KIT C and KIT H, in primary mouse microglial and human neuronal SK-N-SK cells. KIT C and KIT H show antioxidative properties in SK-N-SH cells as well as in primary microglia. In GPR55-knockout SK-N-SH cells, the antioxidative effects are abolished, suggesting a GPR55-dependent antioxidative mechanism. Since inverse agonistic GPR55 activation in the brain seems to be associated with decreased oxidative stress, KIT C and KIT H possibly act as inverse agonists of GPR55 eliciting promising therapeutic options for oxidative stress related diseases

Functional Selectivity of Coumarin Derivates Acting via GPR55 in Neuroinflammation

Anti-neuroinflammatory treatment has gained importance in the search for pharmacological treatments of different neurological and psychiatric diseases, such as depression, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Clinical studies demonstrate a reduction of the mentioned diseases’ symptoms after the administration of anti-inflammatory drugs. Novel coumarin derivates have been shown to elicit anti-neuroinflammatory effects via G-protein coupled receptor GPR55, with possibly reduced side-effects compared to the known anti-inflammatory drugs. In this study, we, therefore, evaluated the anti-inflammatory capacities of the two novel coumarin-based compounds, KIT C and KIT H, in human neuroblastoma cells and primary murine microglia. Both compounds reduced PGE$_{2}$-concentrations likely via the inhibition of COX-2 synthesis in SK-N-SH cells but only KIT C decreased PGE$_{2}$-levels in primary microglia. The examination of other pro- and anti-inflammatory parameters showed varying effects of both compounds. Therefore, the differences in the effects of KIT C and KIT H might be explained by functional selectivity as well as tissue- or cell-dependent expression and signal pathways coupled to GPR55. Understanding the role of chemical residues in functional selectivity and specific cell- and tissue-targeting might open new therapeutic options in pharmacological drug development and might improve the treatment of the mentioned diseases by intervening in an early step of their pathogenesis

Effects of a Novel GPR55 Antagonist on the Arachidonic Acid Cascade in LPS-Activated Primary Microglial Cells

Neuroinflammation is a crucial process to maintain homeostasis in the central nervous system (CNS). However, chronic neuroinflammation is detrimental, and it is described in the pathogenesis of CNS disorders, including Alzheimer’s disease (AD) and depression. This process is characterized by the activation of immune cells, mainly microglia. The role of the orphan G-protein-coupled receptor 55 (GPR55) in inflammation has been reported in different models. However, its role in neuroinflammation in respect to the arachidonic acid (AA) cascade in activated microglia is still lacking of comprehension. Therefore, we synthesized a novel GPR55 antagonist (KIT 10, 0.1–25 µM) and tested its effects on the AA cascade in lipopolysaccharide (LPS, 10 ng / mL)-treated primary rat microglia using Western blot and EIAs. We show here that KIT 10 potently prevented the release of prostaglandin $E_{2}$ ($PGE_{2}$), reduced microsomal $PGE_{2}$ synthase (mPGES-1) and cyclooxygenase-2 (COX-2) synthesis, and inhibited the phosphorylation of Ikappa B-alpha (IκB-α), a crucial upstream step of the inflammation-related nuclear factor-kappaB (NF-κB) signaling pathway. However, no effects were observed on COX-1 and -2 activities and mitogen-activated kinases (MAPK). In summary, the novel GPR55 receptor antagonist KIT 10 reduces neuroinflammatory parameters in microglia by inhibiting the COX-2/$PGE_{2}$ pathway. Further experiments are necessary to better elucidate its effects and mechanisms. Nevertheless, the modulation of inflammation by GPR55 might be a new therapeutic option to treat CNS disorders with a neuroinflammatory background such as AD or depression

Synthesis and SAR evaluation of coumarin derivatives as potent cannabinoid receptor agonists

We report the development and extensive structure-activity relationship evaluation of a series of modified coumarins as cannabinoid receptor ligands. In radioligand, and [S-35]GTP gamma S binding assays the CB receptor binding affinities and efficacies of the new ligands were determined. Furthermore, we used a ligand-based docking approach to validate the empirical observed results. In conclusion, several crucial structural requirements were identified. The most potent coumarins like 3-butyl-7-(1-butylcyclopentyl)-5-hydroxy-2H-chromen-2-one (36b, K-i CB2 13.7 nM, EC50 18 nM), 7-(1-butylcyclohexyl)-5-hydroxy-3-propyl-2H-chromen-2-one (39b, K-i CB2 6.5 nM, EC50 4.51 nM) showed a CB2 selective agonistic profile with low nanomolar affinities. (C) 2021 Published by Elsevier Masson SAS.Peer reviewe

The Diels‐Alder Approach towards Cannabinoid Derivatives and Formal Synthesis of Tetrahydrocannabinol (THC)

Abstract Based on the Diels‐Alder reaction of vinylchromenes with electron‐poor dienophiles, we developed a strategy for the synthesis of tetrahydrocannabinol derivatives. Substituted vinyl chromenes could be converted with several dienophiles to successfully isolate several complex molecules. These molecules already contain the cannabinoid‐like base structure and further processing of one such derivative led to a precursor of Δ9‐tetrahydrocannabinol. The most challenging step towards this precursor was an epoxidation step that was ultimately achieved via dimethyl dioxirane

Anti-neuroinflammatory effects of GPR55 antagonists in LPS-activated primary microglial cells

Abstract Background Neuroinflammation plays a vital role in Alzheimer’s disease and other neurodegenerative conditions. Microglia are the resident mononuclear immune cells of the central nervous system, and they play essential roles in the maintenance of homeostasis and responses to neuroinflammation. The orphan G-protein-coupled receptor 55 (GPR55) has been reported to modulate inflammation and is expressed in immune cells such as monocytes and microglia. However, its effects on neuroinflammation, mainly on the production of members of the arachidonic acid pathway in activated microglia, have not been elucidated in detail. Methods In this present study, a series of coumarin derivatives, that exhibit GPR55 antagonism properties, were designed. The effects of these compounds on members of the arachidonic acid cascade were studied in lipopolysaccharide (LPS)-treated primary rat microglia using Western blot, qPCR, and ELISA. Results We demonstrate here that the various compounds with GPR55 antagonistic activities significantly inhibited the release of PGE2 in primary microglia. The inhibition of LPS-induced PGE2 release by the most potent candidate KIT 17 was partially dependent on reduced protein synthesis of mPGES-1 and COX-2. KIT 17 did not affect any key enzyme involved on the endocannabinoid system. We furthermore show that microglia expressed GPR55 and that a synthetic antagonist of the GPR receptor (ML193) demonstrated the same effect of the KIT 17 on the inhibition of PGE2. Conclusions Our results suggest that KIT 17 is acting as an inverse agonist on GPR55 independent of the endocannabinoid system. Targeting GPR55 might be a new therapeutic option to treat neurodegenerative diseases with a neuroinflammatory background such as Alzheimer’s disease, Parkinson, and multiple sclerosis (MS)