Elisa Perissutti

The Application of Microwave Irradiation as New Convenient Synthetic Procedure in Drug Discovery

Heterocyclic compounds hold a special place among pharmaceutically important natural and synthetic materials. The remarkable ability of heterocyclic nuclei to serve both as biomimetics and reactive pharmacophores has largely contributed to their unique value as traditional key elements of numerous drugs. In both lead identification and lead optimization processes there is an acute need for new organic small molecules. Traditional methods of organic synthesis are orders of magnitude too slow to satisfy the demand for these compounds. The fields of combinatorial and automated medicinal chemistry have been developed to meet the increasing requirement of new compounds for drug discovery, within these fields, speed is of the essence. The efficiency of microwave flash-heating chemistry in dramatically reducing reaction times (reduced from days and hours to minutes and seconds) has recently been proven in several different fields of organic chemistry. We believe that the time saved by using focused microwaves is potentially important in traditional organic synthesis but could be of even greater importance in high-speed combinatorial and medicinal chemistry. In this review, it is impossible to cover all significant developments in the area of microwave-assisted organic synthesis (MAOS). Rather, outlines the basic principles behind the technology and summarizes the areas in which microwave technology has made an impact, to date. Specific attention is given to application of microwave irradiation in liquid systems, and in the solid state as well of several representative biologically interesting nuclei. In addition we report some of the most recently disclosed applications in combinatorial chemistry.

Derivatives as 5HT1A Receptor Ligands-Past and Present

Serotonin is a neuromediator, well-know for its implication in mood regulation, anxiety, depression and, insomnia as well as in normal human function such as sleep, sexual activity and appetite. In this way, serotonin (5-hydroxytryptamine, 5-HT) is one of the most attractive targets for medicinal chemists and pharmaceutical companies. Among 5-HTRs, the 5-HT1A subtype is the best studied, and it is generally accepted that it is involved in psychiatric disorders such as anxiety and depression. Several structurally different compounds are known to bind 5-HT1A receptor sites such as aminotetralins, ergolines, arylpiperazines, indolylalkylamines, aporphines and aryloxyalkyl-amines. In this review, we report an overview of the 5-HT1A receptor ligands, belonging to different chemical classes.

5-HT1A Receptor: An Old Target as a New Attractive Tool in Drug Discovery from Central Nervous System to Cancer

The serotonin receptor subtype 5-HT(1A) was one of the first serotonin receptor subtypes pharmacologically characterized. This receptor subtype has long been object of intense research and is implicated in the pathogenesis and treatment of anxiety and depressive disorders. In recent years, new chemical entities targeting the 5-HT(1A) receptor (alone or in combination with other molecular targets) have been proposed for novel therapeutic uses in neuroprotection, cognitive impairment, Parkinsons disease, pain treatment, malignant carcinoid syndrome, and prostate cancer. This Perspective compares existing data on expression and signaling activity of the 5-HT(1A) receptor to a ligand with an intrinsic agonist or antagonist profile. Our purpose is also to make a complete overview, useful for underlining the features needed to select a specific pharmacological profile rather than another one. This aspect could be really interesting to consider and justify the 5-HT(1A) receptor as a new attractive target for drug discovery.

Synthesis by microwave irradiation and binding properties of novel 5-HT1A receptor ligands

This work reports the synthesis by microwave irradiation and the binding tests on the 5-HT(1A), 5-HT(2A) and 5-HT(2C) receptors of new substituted piperazines in order to identify selective ligands for 5-HT(1A) subtype receptor. Conventional heating and microwave irradiation of the reactions was compared. Synthesis by microwave irradiation gave the desired compounds in better yields than those obtained by conventional heating. The overall times for the syntheses were considerably reduced. Some resulting active compounds (29 and 39) were characterised by a good selectivity profile for the 5-HT(1A) subtype receptor. The more active compounds were selected and further evaluated for their binding affinities on D(1), D(2) dopaminergic and alpha(1), alpha(2) adrenergic receptors. The compound with higher affinity and selectivity for the 5-HT(1A) over all the considered receptors was the 3-[4-[4-(1,2,3,4-tetrahydronaphthyl)-1-piperazinyl]butan]-benzotriazinone (-)29 (5-HT(1A) K(i)=36 nM, other receptors not active).

Microwave enhanced solution synthesis of 1,4-benzodiazepin-5-ones

Abstract Some 2-methyl-1,4-benzodiazepin-5-ones have been synthesized by the application of microwave irradiation. Conventional heating and microwave irradiation of the reactions were compared. Synthesis by microwave irradiation gave the desired compounds in better yields than those obtained by conventional heating. The overall times for the syntheses were considerably reduced.

Microwave-enhanced solution coupling of the α,α-dialkyl amino acid, Aib☆

Abstract The difficult coupling of α-aminoisobutyric acid (Aib), during the synthesis of dipeptides ( 1 – 6 ), was carried out using PyBOP/HOBt and HBTU/HOBt reagents by application of microwave energy in the presence of solvent. Room temperature, conventional heating (oil bath) and microwave irradiation of the reactions are compared. Synthesis by microwave irradiation gave the desired compounds in higher yields and in shorter reaction times than those obtained by conventional heating or at room temperature.

Preparation and local anaesthetic activity of benzotriazinone and benzoyltriazole derivatives

Two sets of benzotriazinone and benzoyltriazole derivatives were prepared and tested for local anaesthetic activity in comparison with lidocaine. Several of the prepared compounds exhibited a fairly good activity comparable or superior to that of lidocaine. The presence of a benzotriazinone or a benzoyltriazole moiety as an aromatic system was quite profitable for both the intensity and duration of activity. The acute toxicity in mice of the four most potent compounds of the series was also assessed. Compound 1b, which has an anaesthetic activity comparable to that of lidocaine, was also characterized by a more favourable therapeutic index. All compounds were tested in vitro to evaluate their negative chronotropic action in isolated rat right atria.

Synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives potassium channel openers

As part of a search for new potassium channel openers, the synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives derived from transformation of the benzopyran skeleton of cromakalim were described. Several new 1,4-benzoxazine derivatives were provided with significant vasorelaxant activity with an overall pharmacological behavior similar to CRK (1f, 1i, 2d, 2e, 2f and 2i).

Synthesis of new 1,2,3-benzotriazin-4-one-arylpiperazine derivatives as 5-HT1A serotonin receptor ligands

A series of novel 1,2,3-benzotriazin-4-one derivatives was prepared and evaluated as ligands for 5-HT receptors. Radioligand binding assays proved that the majority of the novel compounds behaved as good to excellent ligands at the 5-HT1A receptor, some of which were selective with respect 5-HT2A and 5-HT2C receptors. Six analogues (1a, 2a, 2b, 2c, 2e and 2i) were selected and further evaluated for their binding affinities on D1, D2 dopaminergic and alpha1-, alpha2-adrenergic receptors. A o-OCH3 derivative (2e) bound at 5-HT1A sites with subnanomolar affinity (IC50 = 0.059 nM) and shows high selectivity over all considered receptors and may offer a new lead for the development of therapeutically efficacious agents.

Synthesis, biological activity and conformational study of 1,4-benzoxazine derivatives as potassium channel modulators

Abstract With the aim of discovering new molecules with K + -channel activating properties, we have synthesized derivatives of cromakalim (CRK), an important molecule which shows specific affinity towards K + channels, by replacing the benzopyrane ring of this reference compound with a 1,4-benzoxazine moiety. A different number of substituents showing a good discrimination between hydrophobic and electronic properties have been inserted at the 6-position of the 1,4-benzoxazine ring. We describe here the synthesis and discuss the solid state conformation of these new molecules. When tested on rat aorta ring precontracted with phenylephrine, two compounds ( 2c and 2d ) showed a concentration-dependent relaxation similar to that measured for cromakalim but less potent than this reference drug.