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Tesi etd-12192014-175627

Thesis type
Tesi di laurea magistrale LM5
Design and synthesis of heterocyclic derivatives as potential MAGL inhibitors
Corso di studi
relatore Prof.ssa Manera, Clementina
relatore Dott.ssa Arena, Chiara
relatore Prof. Macchia, Marco
Parole chiave
  • Cannabinoid sistem
  • 2-arachidonoylglycerol
  • MAGL
  • eicosanoid
  • arachidonic acid
  • COX-2
  • phenylpiperazine
  • pyrimidilpiperazine
Data inizio appello
Riassunto analitico
The aim of the present thesis work is the design and synthesis of novel compounds as potential MAGL inhibitors, with two fundamental scaffolds, phenylpiperazine and pyrimidylpiperazine.
The endocannabinoid system is implicated in, and regulates, several physiological processes, ranging from food intake and energy balance to pain and inflammation. 2-arachidonoylglycerol (2-AG) is a bioactive lipid able to activate the cannabinoid receptors, CB1 and CB2, which classically mediate its effects. The activity of this bioactive lipid is dependent on its endogenous levels, and therefore by the balance between its production and degradation. It is well known that 2-AG is inactivated through hydrolysis into arachidonic acid and glycerol by Monoacylglycerol lipase (MAGL). Nevertheless, several elements need to be considered to obtain an exact outline of 2-AG metabolism. For instance, although MAGL is the main responsible for controlling 2-AG levels in numerous tissues, two additional α/β-hydrolases domain (ABHD) 6 and 12 can similarly hydrolyze 2-AG. Furthermore recent studies have shown that 2-AG is also substrate of cyclooxygenase (COX)-2. As a consequence, substrate-selective inhibition of COX-2 leads to increased 2-AG levels. According to these findings, it is crucial to understand where and under which circumstances each enzyme is responsible for controlling 2-AG levels for the development of new drugs. Another crucial element to take in consideration when interfering with 2-AG metabolism is that, although 2-AG is a bioactive lipid in its own right, it is also an intermediate in the production of several other bioactive lipids. For instance, MAGL plays a key role in the control of arachidonic acid tissue levels, and thus in the production of prostaglandins during inflammation. Furthermore, 2-AG can be also channelled through COX-2 and subsequent prostaglandin synthase activity leading to the production of prostaglandin glycerol esters (PG-Gs). Altogether these elements demonstrate the close relationship between the endocannabinoid and eicosanoid system and highlight the key role of the metabolism of 2-AG in inflammation-related pathologies (Figure 1).
Finally, in peripheral tissues often MAGL shows changes in other monoacylglycerols, consistent with its lipolytic role as the final step of triglyceride hydrolysis. Indeed, MAGL seems to play a key role in the most aggressive cancer through controlling global FFAs (free fatty acid) levels that serve as the building blocks for synthesis of pro-tumorigenic signaling lipids such as PGE2 and lysophosphatidic acid (LPA).
Therefore, inhibitors of 2-AG metabolism may represent an attractive therapeutic approach for the treatment of pain, inflammation, anxiety, neurodegeneration, cancer and other disorders.

Until now several de novo inhibitors, whose structures do not resemble any endogenous cannabinoid were developed,. They are characterized by a flat structure with a hydrophobic pharmacophoric group connected through a linker to a polar pharmacophore.
In the laboratory where I performed my thesis work, were previously developed compounds with general structure A (Figure 2) as inhibitors of MAGL:

These compounds present all the features typical of MAGL inhibitors: the hydrophobic portion is represented by a phenyl-piperazine moiety; the polar pharmacophore is represented by urea, thiourea, or amide functionality; the spacer is characterized by a three-carbon atom chain. Among these, compound A1 (Figure 3) showed the best inhibitory activity against MAGL.

During the first part of my thesis work I synthesized compound 1 (Figure 4) which presents the same structural features of series A, but it differs from this for the polar pharmacophore that is a carbamate functionality as, since it is well known that carbamate derivatives constitute a good template for inhibiting serine hydrolases.

After, to further study the structure-activity relationships of this class of compounds, it was decided to modify the structure of derivative A1 by linking the pharmacophore group directly to the piperazine ring, and/or by inserting a substituent in para position to the piperazine ring (Figure 5).

My thesis work was inserted in this research project and provided the synthesis of compounds 2-5 (Figure 6).

Recently, a novel class of MAGL inhibitors was reported from a patent (WO2010124121A1)9 developed by Kristen M. and colleagues. These compounds present general structure B (Figure 7) and the most of these derivatives showed interesting inhibitory capacity, on the order of low micromolar/ nanomolar range and the most active inhibitor B1 showed to inhibit MAGL through a reversible mechanism.

Starting from these studies, during the second part of my thesis work, I focused the attention on the design and synthesis of a novel class of potential MAGL inhibitor with general structure C (Figure 8).
These compounds are characterized by a piperazine-pirimidine portion and an amide group as polar pharmacophore, directly linked or separated by a two- or three-carbon atom chain. Three different classes of amide were prepared: 1) phenyl amide derivatives, which gave the best results with the previous series (A); 2) biphenyl amide derivatives, to evaluate the effect of an increase of the hydrophobicity; and 3) the amides derived from (RS)-2-(4-(2-methylpropyl)phenyl)propanoic acid (ibuprofen), since it was recently emerged that the association of a non steroidal anti-inflammatory drug (NSAID) with a compound inhibiting endocannabinoid degradation could be synergistic and open up new therapeutic path for a multitarget approach.