In 1935, Robert Robinson and his colleague William Sage Rapson published a series of articles for the Journal of the Chemical Society. In them, Robinson and Rapson detail how they performed a number of experiments that synthesized molecules similar in structure to sterols. In particular, Part 7 of their experiments describes what is today known in organic chemistry circles and classrooms alike as the Robinson Annulation Reaction. Figures 1 and 2 above demonstrate two examples of the mechanism for the Robinson Annulation Reaction. In Robinson’s words (1935), this reaction involves a ketone that “might undergo double cyclisation” with formation of a new structure (p. 1533). The Robinson Annulation Reaction constructs a new ring (for example, a six-membered ring) from the original starting ketone found in the reactants. Typically, a structure known as an enolate (the anion formed when an alpha hydrogen in the molecule of an aldehyde or a ketone is removed as a hydrogen ion and contains a double bond because it is resonance stabilized—source: science.uvu.edu) would be added to a methyl vinyl ketone or other enone (compound containing a ketone and an alkene). This process is also known as a base-catalyzed Michael addition. Dehydration, or removal of H2O, then occurs to give a cyclohexenone product. The article, “Asymmetric one-pot Robinson annulations” (Rajagopal et al., 2001) describes the procedure of a Robinson Annulation Reaction that converts a five-membered cyclic ketone to a two-ring, bicyclic compound. In this reaction, 1.12 g of 0.01 mol dione was added to a solution of 1.15 g of 0.01 mol S-proline in dry DMSO and mixed in a beaker, followed by 0.7 g of 0.01 mol methyl vinyl ketone. This mixture was stirred for 145 ... ... middle of paper ... ...ucts are in the wrong conformation, the antibiotic will not work affectively in a patient’s system. This is especially useful when there are a set number of starting products, and one wishes to proceed down a chemical pathway in a certain number of steps. This reaction is also utilized as an “environmentally benign approach [to] solvation” (Morrison, et al., 2001) as well as in the production of “complex natural products” in chemical synthesis (Akiyama, et al., 2009). Robinson Annulation is a useful reaction, but not the simplest, so other types of enantioselective synthesis reactions have also been thought up, including “the Lewis acid catalyzed reaction of” regioselective compounds (Huffman, et al., 1985). Lastly, there is a Robinson Annulation Reaction involved in the synthesis of morphine, one of medicine’s basic “pain killer” medications (synarchive.com).
The sole purpose of performing the lab was to utilize aldol condensation reactions to synthesize a cyclopenta-dienone, while using UV spectrophotometry and computer visualization to further understand the dienone. In the beginning of the lab, the tetraphenylcyclopentadienone (TPCP) was synthesized using dibenzyl ketone and benzyl under extremely basic conditions. The synthesis process could be further understood by observing the mechanism portrayed in Figure 1. According to the figure, the dibenzyl ketone will first loose an alpha hydrogen to form the enolate intermediate.
However, it provided insight in the context of Diels-Alder reaction at that time[8] and confirmed the morphine structure proposed by organic chemist Robert Robinson[9]. As a result, many chemists eventually discovered an efficient way to produce morphine. The most prominent of which was developed by Kenner C. Rice which proceeded to make 30% of the product with 14 steps[10]. His method is based on the biomimetric route that follows the Grewe cyclization which corresponds to the morphine biosynthesis[10], as illustrated in Figure
Ever since the discovery of antibiotics in the 1920’s, treating bacterial infections in humans, and animals alike, has emerged as a revolutionary possibility. Antibiotics are drugs that are naturally produced by bacteria or fungus to defend against other bacteria via death or inhibiting reproduction (1). Since their detection, antibiotics have been diversified into many different forms and classes which are arranged by mode of action. Glycopeptides are a class of antibiotics which are composed of glycolsylated cyclic or polycyclic nonribosomal peptides that inhibit cell wall synthesis in susceptible bacteria (2). However, it was soon discovered that the use of these antibiotic drugs would lead to antibiotic resistance. This paper will discuss the history, function, and resistance associated with vancomycin, a glycopeptide antibiotic.
The three butene products have been verified to elute in the following order: 1-butene, trans-2-butene, and cis-2-butene. Theory: The dehydration of 2-butanol, a secondary alcohol, progresses readily in the presence of a strong acid like concentrated sulfuric acid (H2SO4). The reaction is completed via the E1 mechanism. Initially, the hydroxyl group is a poor leaving group, but that is remedied by its protonation by the acid catalyst (H2SO4) converting it to a better leaving group, H2O. The loss of this water molecule results in a secondary carbocation intermediate that continues to form an alkene in an E1 elimination.
Stewart, Philip S, (2001) states that antibiotics are elements that are used to kill, or hinder the multiplication and growth of organisms. Especially, these antibiotics are meant to control fungi and bacteria. In this case, the antibiotics that are used in killing bacteria are referred to as bactericidal, and the ones that are used to prevent the multiplication process are bacteriostatic. The primary microbes for antibiotics are bacteria and fungi. These microorganisms are crucial to facilitate the secretion of substances that kill harmful bacteria which confer competition for the limited available nutrients (Southern, P. J., &Berg, 1981).
Reacting 1-butanol produced 2-trans-butene as the major product. 1-butanol produces three different products instead of the predicted one because of carbocation rearrangement. Because of the presence of a strong acid this reaction will undergo E1 Saytzeff, which produces the more substituted
The competing enantioselective conversion method uses each enantiomer of a kinetic resolution reagent, in this case R-HBTM and S-HBTM, in separate and parallel reactions, where the stereochemistry of the secondary alcohol is determined by the rate of the reactions. When using the CEC method, the enantiomer of the secondary alcohol will react with one enantiomer of the HBTM acyl-transfer catalyst faster than with the other HBTM enantiomer. The mnemonic that identifies the absolute configuration of the secondary alcohol is as follows: if the reaction is faster with the S-HBTM, then the secondary alcohol has the R-configuration. In contrast, if the reaction is faster with the R-HBTM, then the secondary alcohol has the S-configuration. Thin layer chromatography will be used to discover which enantiomer of HBTM reacts faster with the unknown secondary alcohol. The fast reaction corresponds to a higher Rf spot (the ester) with a greater density and a slower reaction corresponds to a lower Rf spot with high de...
Compounding all of these solutions, the pharmaceutical industry needs to conduct extensive research on developing new antibiotics for various pathogenic bacteria by studying the bacterial structure. This will help scientists to formulate ways of counteracting the functions of the various constituents of bacteria.
Dr.Grundmann, Oliver, Fundamental of Pharmaceutical chemistry (PHA6432), Module 1, Drug action and drug discovery, Fall 2015
In the last decade, the number of prescriptions for antibiotics has increases. Even though, antibiotics are helpful, an excess amount of antibiotics can be dangerous. Quite often antibiotics are wrongly prescribed to cure viruses when they are meant to target bacteria. Antibiotics are a type of medicine that is prone to kill microorganisms, or bacteria. By examining the PBS documentary Hunting the Nightmare Bacteria and the article “U.S. government taps GlaxoSmithKline for New Antibiotics” by Ben Hirschler as well as a few other articles can help depict the problem that is of doctors prescribing antibiotics wrongly or excessively, which can led to becoming harmful to the body.
The product was recrystallized to purify it and the unknown filtrate and nucleophile was determined by taking the melting points and performing TLC. Nucleophilic substitution reactions have a nucleophile (electron pair donor) and an sp3 electrophile (electron pair acceptor) with an attached leaving group. This experiment was a Williamson ether synthesis usually SN2, with an alkoxide and an alkyl halide. Conditions are favored with a strong nucleophile, good leaving group, and a polar aprotic solvent.
The discovery of antibiotics is attributed to Alexander Fleming who discovered the first antibiotic to be commercially used (Penicillin) in approximately 1928. An antibiotic, also known as an antimicrobial, is a medication that is taken in order to either destroy or slow the growth rate of bacteria. Antibiotics are integral to the success of many medical practises, such as; surgical procedures, organ transplants, the treatment of cancer and the treatment of the critically ill. (Ramanan Laxminarayan, 2013)
One of the greatest achievements in the 20th century was the invention and mass production of antibiotics. Antibiotics or antimicrobials are chemical drugs that are used to treat a variety of different infectious bacterial diseases by destroying or slowing the growth of the bacteria. Antibiotics are toxic to the target cell but do not harm the host. They are designed to attack various kinds of parasites, fungus, and bacteria. Contrary to popular belief antibiotics do not work against viruses like those that cause the common cold. Antibiotics are broken down into different classifications because antibiotics are selective killers, which mean that it has been manufactured to kill a certain malicious bacteria strain. Each antimicrobial differs from one another by their physical and chemical properties and by their antibacterial spectrum of activity. The different kinds of antibiotics fight off the infection in different ways. The different ways the antibiotic functions is by inhibiting the bacterial cell from metabolizing, by preventing the bacteria’s cell wall synthesizing, by creating a permeable membrane of the bacteria cell, or by suppressing nucleic acid transcription and replication. Most antibiotics today are semisynthetic, which means their natural derivative has been altered. Antibiotics have two distinct groups that was separated by their effect on bacteria. Bactericidal antimicrobials kills bacteria while bacteriostatic agents hinder the bacteria from growing or reproducing. They are also seperated depending on their activity sepectrum. Narrow antibiotics target a spesfic group of bacteria while a broad spectrum targets many different kinds of cells.
Stereochemistry come to the learning of the relative placement of atoms that form the structure of molecules and their use. An essential subdivision of stereochemistry is the learning of chiral molecules. Stereochemistry is also known as 3D chemistry because the prefix "stereo-" means "three-dimensionality”. The learning of stereochemistry centering on stereoisomers and spans the whole range of organic, inorganic, biological, physical and especially supramolecular chemistry. There is some grandness of stereochemistry. Firstly, is the thalidomide incident. Thalidomide is a medicament drug, first processed in 1957 in Germany, appointed for treating morning illness in pregnant women. The drug was revealed to be teratogenic, causing sincere genetic harm to early embryonic growth and development, leading to limb distortion in babies. Some of the several planned mechanisms of teratogenicity touch on various biological purpose for the (R) - and the (S)-thalidomide enantiomers. In the human body however, thalidomide undergoes racemization whereby justified if only one of the two enantiomers is apply as a drug, the other enantiomer is produced as a outcome of metabolism. Accordingly, it is wrong to state that one of the stereoisomer is harmless while the other is teratogenic. Next, the properties of many drugs rely on their stereochemistry. For information:
Miller SL, and Urey HC. 1959 Organic Compound Synthesis on the Primitive Earth. Science 130,