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Pivaloyloxymethyl
Pivaloyloxymethyl (POM, pivoxil, pivoxyl) is a protecting group used in organic synthesis.''Protective Groups in Organic Synthesis'', 3rd Edition, Theodora M. Greene and Peter G. M. Wuts, The POM radical has the formula (CH3)3C-CO-O-CH2. The POM group is also sometimes used to produce prodrugs. For example, the POM group can be attached to a negatively charged organophosphate group(s) of a drug causing a neutralization of the negative charge, which can allow the drug to become more lipid-soluble and thus more able to diffuse passively across cell membranes into cells. Upon entry into cells, the POM portion of the molecule can be removed by cellular processes resulting in release of active drug. Clinically used prodrugs containing pivaloyloxymethyl groups include adefovir dipivoxil, pivampicillin, cefditoren pivoxil, pivmecillinam, and valproate pivoxil. Tenofovir disoproxil contains a very similar prodrug group. See also * Pivalic acid Pivalic acid is a carboxylic acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pivaloyloxymethyl
Pivaloyloxymethyl (POM, pivoxil, pivoxyl) is a protecting group used in organic synthesis.''Protective Groups in Organic Synthesis'', 3rd Edition, Theodora M. Greene and Peter G. M. Wuts, The POM radical has the formula (CH3)3C-CO-O-CH2. The POM group is also sometimes used to produce prodrugs. For example, the POM group can be attached to a negatively charged organophosphate group(s) of a drug causing a neutralization of the negative charge, which can allow the drug to become more lipid-soluble and thus more able to diffuse passively across cell membranes into cells. Upon entry into cells, the POM portion of the molecule can be removed by cellular processes resulting in release of active drug. Clinically used prodrugs containing pivaloyloxymethyl groups include adefovir dipivoxil, pivampicillin, cefditoren pivoxil, pivmecillinam, and valproate pivoxil. Tenofovir disoproxil contains a very similar prodrug group. See also * Pivalic acid Pivalic acid is a carboxylic acid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adefovir Dipivoxil
Adefovir is a prescription medicine used to treat (chronic) infections with hepatitis B virus. A prodrug form of adefovir was previously called bis-POM PMEA, with trade names Preveon and Hepsera. It is an orally administered nucleotide analog reverse-transcriptase inhibitor (ntRTI). It can be formulated as the pivoxil prodrug adefovir dipivoxil. Uses It is used for treatment of hepatitis B. Trials of adefovir in patients with HIV have not shown any clear benefits. History Adefovir was invented in the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic by Antonín Holý, and the drug was developed by Gilead Sciences for HIV with the brand name Preveon. However, in November 1999, an expert panel advised the U.S. Food and Drug Administration (FDA) not to approve the drug due to concerns about the severity and frequency of kidney toxicity when dosed at 60 or 120 mg. The FDA followed that advice, refusing to approve adefovir as a treatment ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protecting Group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many preparations of delicate organic compounds, some specific parts of their molecules cannot survive the required reagents or chemical environments. Then, these parts, or groups, must be protected. For example, lithium aluminium hydride is a highly reactive but useful reagent capable of reducing esters to alcohols. It will always react with carbonyl groups, and this cannot be discouraged by any means. When a reduction of an ester is required in the presence of a carbonyl, the attack of the hydride on the carbonyl has to be prevented. For example, the carbonyl is converted into an acetal, which does not react with hydrides. The acetal is then called a protecting group for the carbonyl. After the step involving the hydride is complete, the acet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: ''total synthesis'', ''semisynthesis'', and ''methodology''. Total synthesis A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available petrochemical or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a ''linear'' synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. Most often, each step in a synthesis refers to a separate rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical (chemistry)
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉) which have two unpaired electrons. Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations. Radicals are important in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. A majority of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prodrug
A prodrug is a medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be used to improve how the drug is absorbed, distributed, metabolized, and excreted (ADME). Prodrugs are often designed to improve bioavailability when a drug itself is poorly absorbed from the gastrointestinal tract. A prodrug may be used to improve how selectively the drug interacts with cells or processes that are not its intended target. This reduces adverse or unintended effects of a drug, especially important in treatments like chemotherapy, which can have severe unintended and undesirable side effects. History Many herbal extracts historically used in medicine contain glycosides (sugar derivatives) of the active agent, which are hydrolyzed in the intestines to release the active and more bioavailable aglycone. For example, salicin is a β-D-glucopyranosid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organophosphate
In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered as esters of phosphoric acid. Like most functional groups, organophosphates occur in a diverse range of forms, with important examples including key biomolecules such as DNA, RNA and ATP, as well as many insecticides, herbicides, nerve agents and flame retardants. OPEs have been widely used in various products as flame retardants, plasticizers, and performance additives to engine oil. The popularity of OPEs as flame retardants came as a substitution for the highly regulated brominated flame retardants. The low cost of production and compatibility to diverse polymers made OPEs to be widely used in industry including textile, furniture, electronics as plasticizers and flame retardants. These compounds are added to the final product physica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lipophilicity
Lipophilicity (from Greek λίπος "fat" and φίλος "friendly"), refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such non-polar solvents are themselves lipophilic (translated as "fat-loving" or "fat-liking"), and the axiom that "like dissolves like" generally holds true. Thus lipophilic substances tend to dissolve in other lipophilic substances, but hydrophilic ("water-loving") substances tend to dissolve in water and other hydrophilic substances. Lipophilicity, hydrophobicity, and non-polarity may describe the same tendency towards participation in the London dispersion force, as the terms are often used interchangeably. However, the terms "lipophilic" and "hydrophobic" are not synonymous, as can be seen with silicones and fluorocarbons, which are hydrophobic but not lipophilic. __TOC__ Surfactants Hydrocarbon-based surfactants are compounds that are amphiphilic (or amphipathic), having a hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to ions a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pivampicillin
Pivampicillin is a pivaloyloxymethyl ester of ampicillin. It is a prodrug, which is thought to enhance the oral bioavailability of ampicillin because of its greater lipophilicity compared to that of ampicillin. Adverse effects Prodrugs that release pivalic acid when broken down by the body—such as pivampicillin, pivmecillinam, and cefditoren pivoxil—have long been known to deplete levels of carnitine. This effect is not due to the drug itself but to pivalate, which is mostly removed from the body by forming a conjugate with carnitine. Although short-term use of these drugs can cause a marked decrease in blood levels of carnitine, it is unlikely to be of clinical significance; long-term use, however, is not recommended. Availability Worldwide, pivampicillin is only available in Denmark, where it is sold as Pondocillin® by PharmaCoDane, or Miraxid® by LEO Pharma LEO Pharma A/S is a multinational Danish pharmaceutical company, founded in 1908, with a presence in about 100 co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cefditoren Pivoxil
Cefditoren, also known as cefditoren pivoxil is an antibiotic used to treat infections caused by Gram-positive and Gram-negative bacteria that are resistant to other antibiotics. It is mainly used for treatment of community acquired pneumonia. It is taken by mouth and is in the cephalosporin family of antibiotics, which is part of the broader beta-lactam group of antibiotics. Structure Like other cephalosporins, cefditoren has a β-lactam ring at the 7 position of cephalosporin ring that is responsible for its inhibitory action on bacterial cell wall synthesis. In addition to the cephem nucleus common to all cephalosporins, cefditoren has an aminothiazole group that enhances its activity against Gram-negative organisms, a methylthiazole group that enhances its activity against Gram-positive organisms, a methoxyimino group that gives it stability against β-lactamases, and a pivoxil ester group that enhances oral bioavailability. Antimicrobial activity The spectrum of cefdi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pivmecillinam
Pivmecillinam (INN) or amdinocillin pivoxil (USAN, trade names Selexid, Penomax and Coactabs) is an orally active prodrug of mecillinam, an extended-spectrum penicillin antibiotic. Pivmecillinam is the pivaloyloxymethyl ester of mecillinam. Pivmecillinam is only considered to be active against Gram-negative bacteria, and is used primarily in the treatment of lower urinary tract infections. In the Nordic countries, it has been widely used in that indication since the 1970s. It has been proposed as the first-line drug of choice for empirical treatment of acute cystitis. It has also been used to treat paratyphoid fever and shigellosis. Activity Adverse effects The adverse effect profile of pivmecillinam is similar to that of other penicillins. The most common side effects of mecillinam use are rash and gastrointestinal upset, including nausea and vomiting. Retrieved on August 31, 2008. Prodrugs that release pivalic acid when broken down by the body — such as pivmecillinam, pi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
