Years of cumulative research can result in the development of a clinically useful drug, providing either a cure for a particular disease or symptomatic relief from a physiological disorder. A lead compound with a desired pharmacological activity may have associated with it undesirable side effects, characteristics that limit its bioavailability, or structural features which adversely influence its metabolism and excretion from the body. Bioisosterism represents one approach used by the medicinal chemist for the rational modification of lead compounds into safer and more clinically effective agents. The concept of bioisosterism is often considered to be qualitative and intuitive.1 The prevalence of the use of bioisosteric replacements in drug design need not be emphasized. This topic has been reviewed in previous years.2-5 The objective of this review is to provide an overview of bioisosteres that incorporates sufficient detail to enable the reader to understand the concepts being delineated. While a few popular examples of the successful use of bioisosteres have been included, the George Patani graduated with a B.Pharm. in 1992 from the College of Pharmaceutical Sciences, Mangalore University at Manipal, India. In 1996, he received his M.S. in Pharmaceutical Science at Rutgers University under the direction of Professor Edmond J. LaVoie. He is presently pursuing graduate studies in pharmaceutics. His current research interests are focused on drug design and controlled drug delivery.

https://www.mch.estranky.sk/file/228/1996chemrev96-3147-76_bioisosterism.pdf

Bioisosterism: A Rational Approach in Drug Design.

Fluorine has received great attention in all fields of science. “Small atom with a big ego” was the title of the Symposium at the ACS meeting in San Francisco in 2000, where a number of the current scientific and industrial aspects of fluorine chemistry made possible by the small size and high electronegativity of the atom were discussed. This small atom has provided mankind with significant benefits in special products such as poly(tetrafluroethylene) (PTFE), freon, fluoro-liquid crystals, optical fiber, pharmaceutical and agrochemical compounds, and so on, all of which have their own unique properties that are otherwise difficult to obtain.1 For instance, at present, up to 30% of agrochemicals and 10% of pharmaceuticals currently used contain fluorine atoms. Therefore, organic fluorine compounds have received a great deal of interest and attention from the scientists involved in diverse fields of science and technology. Now, not only C-F bond formation but also selective C-F bond activation have become current subjects of active investigation from the viewpoint of effective synthesis of fluoroorganic compounds. The former is highlighted by designing a sophisticated fluorinating reagent for regioand stereocontrolled fluorination and developing versatile multifunctional and easily prepared building blocks. C-F bond formation has been treated extensively in several reviews2 and books.3 The latter is a subject that has been less explored but would be promising for selective defluorination of aliphatic fluorides, cross-coupling with aryl fluorides, and * To whom correspondence should be addressed. Phone: 81-78-803-5799. Fax: 81-78-803-5799. E-mail: amii@kobe-u.ac.jp and uneyamak@cc.okayamau.ac.jp. † Kobe University. ‡ Okayama University. Chem. Rev. 2009, 109, 2119–2183 2119

C-F bond activation in organic synthesis.

3.1. Chelation 564 3.2. Acid−Base Character 564 3.3. Photochemistry 565 4. In Vitro Antimicrobial Spectra 566 5. Structure−Activity Relationships 568 5.1. N-1 Ethyl Family 568 5.2. N-1 Cyclopropyl Family 568 5.3. N-1 to C-8 Bridged (Tricyclic) Family 568 5.4. N-1 Aryl Family 569 5.5. Positions C-2, C-3, and C-4 570 5.6. C-4a Substituted Analogues 571 5.7. C-5 Substituents 571 5.8. C-6 Substituents 571 5.9. C-7 Substituents 571 5.9.1. Piperazinyl and Related Moieties 572 5.9.2. Pyrrolidinyl and Related Moieties 572 5.9.3. Cyclobutylaminyl and Related Moieties 572 5.9.4. Bicycloaminyl Moieties 572 5.9.5. Carbon-Linked Substituents 572 5.10. Substituents at C-8 573 5.11. Resume of Structure−Activity Relationships of Quinolones 573

Bacterial topoisomerase inhibitors: quinolone and pyridone antibacterial agents.

Sustainable metal-based catalysts for the synthesis of cyclic carbonates containing five-membered rings

A number of 7-substituted quinolone derivatives were synthesized and evaluated for antibacterial and cytotoxic activities. Preliminary results indicated that most compounds tested in this study demonstrated better activity against methicillin-resistant Staphylococcus aureus than norfloxacin. Among them, 1-(4-amino-2-fluorophenyl)-6-fluoro-1,4-dihydro-7-[4-[2-(4-methoxyphenyl)-2-hydroxyiminoethyl]-1-piperazinyl]-4-oxo-3-quinolinecarboxylic acid (11d) and its ketone precursor 10d exhibited significant activities against Klebsiella pneumoniae, methicillin-resistant S. aureus, erythromycin- and ampicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecalis. Due to strong cytotoxicities of 11d (a mean log GI(50) of -5.40), compound 10d, with good antibacterial activities and low cytotoxicities (a mean log GI(50) of -4.67), is a more potential drug candidate.

https://ir.kmu.edu.tw/retrieve/10338/805006-3.pdf

Synthesis and Antibacterial Evaluation of Certain Quinolone Derivatives

A series of 2-(4-substituted-1-(homo)piperazinyl)benzimidazoles was prepared and tested for H1-antihistaminic activity in vitro and in vivo. Most of the compounds showed antihistaminic activity and some of the 1-[2-(substituted-oxy)ethyl] derivatives exhibited potent activity. In a structure-activity comparison it was found that the oxygen atom in the 2-(substituted-oxy)ethyl group at the 1-position of the benzimidazole nucleus played an important role for potent antihistaminic activity, especially in vivo. One of the most potent compounds, 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole (69), was 39 times more potent than chlorpheniramine maleate in H1-antihistaminic activity in vivo and was selected for clinical evaluation. The structure of compound 69 is of interest because it provides only a single aromatic unit linked through a chain to a basic nitrogen, while most H1-antihistaminic agents have structures that comprise a double-aromatic unit linked through a chain to a basic tertiary amino group.

Synthesis of 2-(4-substituted-1-piperazinyl)benzimidazoles as H1-antihistaminic agents.

It is known that thiazolo[3,2-a][1,8]naphthyridine derivatives (3a) exhibit good antibacterial activity. Accordingly, several analogues of 3a, viz. oxazolo- and imidazolo[3,2-a][1,8]naphthyridine derivatives 3b and 3c, were synthesized and evaluated for antibacterial activity in vitro and for inhibitory activity against DNA gyrase of Escherichia coli K-12 C600. Compound 3a exhibited antibacterial activity comparable to that of ofloxacin and enoxacin against Gram-positive and Gram-negative bacteria and displayed antibacterial activity superior to that of 3b and 3c. The antibacterial activities of 3b and 3c decreased in that order. DNA gyrase inhibitory activities of 3a-c in E. coli K-12 C600 paralleled their in vitro antibacterial activity. It was found that enhancement of the DNA gyrase inhibitory activity of 3a was dependent on a certain feature of the sulfur atom of the thiazole ring.

Synthesis and antibacterial activity of thiazolo-, oxazolo-, and imidazolo[3,2-a][1,8]naphthyridinecarboxylic acids.

Structural modification and the coronary vasodilator activity of the calcium antagonist fostedil (KB-944) are described. Elimination of the bezothiazole ring or replacement of the benzothiazole ring of fostedil with other hetero rings leads to a decrease in vasodilator activity. Change of the distance from the aromatic ring to the phosphorus of fostedil causes a decrease in the activity. The present study indicates that the presence of an aromatic ring substituted thiazole ring and the presence of phosphonate at an appropriate distance from the thiazole ring are important for the coronary vasodilator action of fostedil.

Organic phosphorus compounds. 2. Synthesis and coronary vasodilator activity of (benzothiazolylbenzyl) phosphonate derivatives.

Several 3-formylquinolone derivatives (8a-c) were synthesized to assay the antibacterial activity both in vitro and in vivo. In vitro, all of the compounds 8a-c showed lower activity than that of the corresponding 3-carboxyl compounds 1a-c, and in vivo, they showed higher activity than that of compounds 1a-c. After oral administration of 3-formyl compounds 8a-c to mice, the compounds were rapidly metabolized into 3-carboxyl compounds 1a-c. In particular, the 3-formyl derivative (8a) of norfloxacin (NFLX, 1a) gave a 2-fold higher serum level than that of NFLX and functioned as a prodrug of NFLX.

Studies on prodrugs. 7. Synthesis and antimicrobial activity of 3-formylquinolone derivatives.

A series of 1-benzyl-4-diphenylmethylpiperazines was prepared and tested for cerebral vasodilating activity. Among the compounds with stronger potency and longer-lasting action than papaverine, the most potent analog 19 (KB-2796) was selected for further study. Some pharmacological properties of 19 are presented.

Goro Tsukamoto

Papers

Synthesis of 2-(4-substituted-1-piperazinyl)benzimidazoles as H1-antihistaminic agents.

Synthesis and antibacterial activity of thiazolo-, oxazolo-, and imidazolo[3,2-a][1,8]naphthyridinecarboxylic acids.

Organic phosphorus compounds. 2. Synthesis and coronary vasodilator activity of (benzothiazolylbenzyl) phosphonate derivatives.

Studies on prodrugs. 7. Synthesis and antimicrobial activity of 3-formylquinolone derivatives.

Benzylpiperazine Derivatives. IV. Syntheses and Cerebral Vasodilating Activities of 1-Benzyl-4-diphenylmethyl-piperazine Derivatives