(2006), after slight modifications. The fundamental principle of the DPPH method is the reduction of the DPPH radical in an ethanolic solution by an H-donator antioxidant (AH) to form the non-radical form DPPH-H. In a microtube, 10 µL of each fraction at different concentrations (10 - 1000 µg/mL) were mixed with 990 µL of a DPPH solution (0.1mM) prepared daily. The reaction was allowed to develop for 30 minutes in the dark at room temperature, and then the absorbance was read at 515 nm with a spectrophotometer (Spectronic Helios Alpha UV-Visible, Thermo Electron Corporation, U.S.A). The analysis was done in triplicate for each
CHAPTER III BIGINELLI REACTION INTRODUCTION Dihydropyrimidinones (DHPMs), commonly known as Biginelli compounds, have attained unprecedented attention due to its greater biological, pharmaceutical and therapeutic properties. In 1893, Pietro Biginelli reported the first synthesis of 3,4-dihydroprimidin-2(1H)ones (DHPM) by a very simple multi-component one-pot condensation reaction of an aromatic aldehyde, urea and ethyl acetoacetate in ethanolic solution1 (Scheme 1.1). This efficient approach to partly reduced pyrimidines, termed the Biginelli reaction or condensation, was largely ignored in the following years, and therefore, also the synthetic potential of these multi-functionalized dihydropyrimidines remained unexplored. In recent years, however, interest in these compounds has increased rapidly, and the scope of the original cyclocondensation reaction has been widely extended by variation of all three components. Scheme 1.1.
1.3. An Overview for the Synthesis of Tetrahydropyrans, Piperidines and Dihydro-γ-pyrone Derivatives To build this class of heterocycles, many strategies have been developed over the years. The most widely used methods are the Prins cyclization, hetero-Diels–Alder (HDA) cyclization, oxonium-ene cyclization, the intramolecular Michael additions and ring-closing metathesis. Other strategies include electrophile-induced cyclizations of non-activated alkenes and Lewis acid promoted cyclizations of epoxy alcohols/amines. Reported methods used for six membered oxygen and nitrogen ring synthesis have their own advantages and disadvantages.
purified through preparative LC as described above and finally characterized as phloretin and phloridzin (Fig. 1). Compound 1 3-(4-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one or phlorizin was obtained as amorphous powder, mp 2620C. The UV/Visible spectrum of the compound showed λmax at 225 and 285 nm. ESI–MS m/z 297 [M+Na]+ in positive ion mode and 273 [M-H] in negative ion mode for molecular formula C15H14O5; 274.
6). RP-HPLC program: 0-5 min 5-30 min 30-35 min 20% MeCN 20-85% MeCN 85-99% MeCN 5-{3-(3-N-polyethyleniminemaleimide)propylamidophenyl}-10,15,20-tris(4-sulfonato-phenyl)porphyrin trisodium salt (TPPS-PEI) (8b) TPPS-Mal (20 mM) in 500 μL of dry DMF was titrated to 500 μL of 40 mM polyethylenimine in dry DMF. After stirring at room temperature for 8 h additional 0.5 ml of 40 mM PEI were added. The solution mixture was kept with stirring overnight. The solvent was removed under reducing
The main objective of this experiment was the formation of phenacetin from the synthesis of acetaminophen. This was done through a chemical reaction known as the Williamson ether synthesis using techniques of refluxing, vacuum filtration and recrystallization incorporating a mixed solvent system. A further objective of this experiment was to study the formation of the product (phenacetin). Such validation was completed by using techniques for determining the melting point, calculating percent yield, and IR (infrared spectroscopy) of the resultant product. Our reaction yielded 3.696% of phenacetin product.
Quantification and trypsin digestion of polypeptides Protein concentration was estimated by Bradford assay, and 100µg of total protein from each sample was subjected to in-solution trypsin digestion to generate peptides. Initially, treating the sample with 5µl of 100mM dithiothreitol in 50 mM ammonium bicarbonate for 30 min at 60ºC and alkylation with 200mM iodoacetamide in 50 mM ammonium bicarbonate at room temperature for 30 minutes reduced the protein disulphide bonds. Proteins were then digested with 4µg of sequencing grade-modified trypsin (Sigma) in 50 mM ammonium bicarbonate by incubating overnight at 37ºC. The trypsin digestion reaction was stopped by 1µl of 100% formic acid. The digested peptide solutions were centrifuged at 14000
Hardee and his group developed a process of activation of aliphatic carboxylic acids taking 3, 3-dichlorocyclopropenes in presence of tertiary amine base , DIPEA (diisopropylethylamine)[22] FIGURE 3.3 ACTIVATION OF ALIPHATIC ACID Racemization is frequent in the course of coupling reaction at the C-terminal amino acid residue due to the ionization of the α-hydrogen atom and formation of an oxazolone intermediate in peptide synthesis, so of course this will not reagent of choice in peptide synthesis, where suitable peptide coupling reagent can be selected, which is out of scope of this review. [22] 3.2 SELECTED PROCESS Out of all the processes mentioned in the survey, these processes were selected on the behalf of having most appropriate reaction conditions and environment of the research lab, i.e modification with
The photolysis of the azirine with the shortwavelength light (>300 nm) caused the C-C bond cleavage of the 2H-azirine ring to produce the nitrile ylide.31 The C,C-dicyanoketenimines were generated by flash vacuum thermolysis of ketene N,S-acetals or by thermal or photochemical decomposition of alpha-azido-beta-cyanocinnamonitrile. In the latter reaction, 3,3-dicyano-2-phenyl-1-azirine 12 is also formed. Nucleophilic substitution reactions of 2-halo- 2H-azirines with potassium phthalimide and aniline allowed the preparation of substituted 2H-azirines. The reactions of 2-bromo-2H-azirine with methylamine led to the synthesis of alpha-diimines. 2-Halo- 2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 10a-10d, 3-oxazoline, and 2H-[1,4]oxazines.32 Chemical reactions are described for the formation of aziridine-2-one and di-azirine-3-one derivatives as potential precursors for the original synthesis of amino-acids, proteins, pyrimidines, purines, nicotinamide and flavin.33
5-Aminolaevulinic acid (ALA) and porphobilinogen are reported as the early precursors in the haem biosynthetic pathway [11]. Using ALA in both aerobic and anaerobic organism after their biosynthesis in a specific way depending on the type of organism involve, the formation of the porphyrin and haem from the precursor ALA species are commonly proceeded with same sequence of reactions in all these species .The condensation of two molecules of ALA by the enzyme dehydratase gives first ring structure, porphobilinogen (PBG) [12]. The condensation of four PBG molecules in the presence of two enzymes, PGB deaminase and pophyrinogen cosynthetase results in formation of a four ring structure, uroporphyrinogen with side chain mainly comprising of acetic and propanoic acid. The decarboxylation of the acetic acid side chain of uroporphyrinogen to methyl group by enzyme uroporphyrinogen decarboxylase results in the formation of coproporphyrinogen. The oxidative decarboxylation of the propanoic side chain to vinyl group in the presence of enzyme coproporphyrinogen oxidase gives rise to Protoporphrinogen IX [13].