Amides spectroscopic analysis

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

It is a supposition that the )9-sheet structure of neurotoxin is an essential structural element for binding to the receptor. The presence of -sheet structure was found by Raman spectroscopic analysis of a sea snake neurotoxin (2). The amide I band and III band for Enhydrina schistosa toxin were at 1672 cm and 1242 cm" respectively. These wave numbers are characteristic for anti-parallel -sheet structure. The presence of -sheet structure found by Raman spectroscopic study was later confirmed by X-ray diffraction study on Laticauda semifasciata toxin b. 

These achiral poly(A -propargylamides) form helices with an equivalent amount of right- and left-handed screw senses. Addition of chiral alcohols induces predominantly one-handed screw sense in polyl7a and polyl7d. NMR spectroscopic analysis has revealed that the amide side chains interact with optically active alcohols by hydrogen bonding. Terpenes also induce a one-handed helix. In this case, hydrophobic interaction plays an important role for helix induction. 

The structure of bursatellin, a metabolite from the Puerto Rican sea hare Bursatella leachii pleii (389), was revised to be 483, possessing an N-formyl amide functionality, by detailed spectroscopic analysis using the compound (483) isolated from the Mediterranean B. leachii leachii and B. leachii savignyana (390). The optical rotation of bursatellin (483) from the Mediterranean sample, however, was of opposite sign to that reported... 

De Diego T, Lozano P, Gmouh S et al (2004) Fluorescence and CD spectroscopic analysis of the a-chymotrypsin stabilization by the ionic liquid, l-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide. Biotechnol Bioeng 88 916-924... 

For the final part (Scheme 5.3), the 20-carbon chain of fumonisin Bj was coupled from the Uthium acetylide derived from 273 and the Weinreb amide 279 (233). After enantioselective reduction of the alkynyl ketone 281 (234, 235), the C-10 stereochemistiy was set, followed by benzyl ether formation and acid-catalyzed acetonide removal, to provide diol 282 (236). Using tricarballylic acid dibenzyl ester, the two hydroxy groups were esterified (237) and the hydrogenation of the azide, the alkyne, and the benzylic ethers led to the target product, fumonisin Bj (249). The spectroscopic analysis matched with those of commercial fumonisin Bj and further experiments on the synthetic material showed inhibitoiy activity on sphingoUpid biosynthesis. 

A PRS structure is only possible for PG, and is ruled out by the evidence for an APRS structure for this polypeptide. However, the normal modes of PRS PG have also been calculated [82], It is interesting that, when multisheet TDC coupling is included, the strong Raman amide I mode is predicted to be at a much lower frequency than the strong IR amide I mode, just the opposite of what is observed and predicted for the APRS structure. This demonstrates the power of detailed vibrational spectroscopic analysis in revealing fine details of polypeptide structure. 

A series of D,D-dialkyl 2-oxo-2- 4-(selenomorpholinosulfonyl)phenyla-mino) ethylphosphonates (37) has been synthesized and their structures confirmed by IR, H and P NMR spectroscopy and mass spectrometry. Other papers on phosphonate esters have used principally H and C NMR spectroscopy including a facile diastereoselective synthesis of phosphonate esters bearing cyclic or acyclic amides and a study of structural isomers of pyridinephosphonic acids. Some novel iminophosphoranes have been synthesized and characterized by IR, NMR ( H, C and and solely H NMR in addition to mass spectroscopic analysis. The crystal synthesis, structure (by XRD) and characterization of a new organic... 

The spectroscopic analysis and various physical, dielectric, and electrical properties of odd-numbered nylons have been sumtxtarized. Odd-numbered nylons sb polymorphism. Nylon-11 shows at least live different crystal forms. The y form seems to be the most common polymorph in many odd-numbered nylons. The piezoelectric and ferroelectric behaviors fA odd-numbered nylons such as nylon-7 and nykm-11 are comparable or belter than for PVDF and depend on the crystal form. The desired stability of the piezoelectric response in odd-munbered nylons is related to the ferroelectric reorientation of the amide group dipoles followed by densely packed hydrogen-bonded sheets in the crystalline regions induced by poling and annealing. 

As noted earlier, hard tissues are composite materials consisting of mineral and organic matrix. In Raman spectroscopic analysis, the organic matrix is identified by methylene side chains (CH2 at 1450 cm" ), amide III ( 1200-1300 cm" ), amide I ( 1620-1700cm ), phenylalanine (1002cm ) or the combined proline (921 and 855 cm ), and hydroxyproline (876 cm ) bands [2, 27, 208-210]. 

The physical and spectroscopic properties of /V-acyloxy-A-alkoxyamides confirm pyramidality at nitrogen and the disconnection of the nitrogen lone pair from the amide carbonyl. The presence of an acyloxyl and an alkoxyl group at nitrogen also results in an anomeric interaction between the oxygens, which is facilitated by the sp3-hybridised nitrogen. Experimental observations, including X-ray analysis are fully supported by results from computational chemistry. 

GC analyses of the pupal secretion of E. borealis have indicated the presence of vitamin E acetate and other tocopherol derivatives [49,50]. However, in tests with ants, these compounds proved to be essentially inactive, whereas the secretion itself was potently deterrent. To find and identify the active components in the pupal Epilachna borealis secretion, NMR spectroscopic studies on the fresh secretion were carried out. One and two-dimensional NMR experiments revealed that the tocopheryl acetates account for only a relatively small percentage of the beetles5 total secretion (20%), whereas the major components represented a group of previously undetected compounds. By analysis of the COSY, HSQC and HMBC spectra of the mixture, these components were shown to be esters and amides derived from three (co-l)-(2-hydroxyethylamino)alka-noic acids 44-46. HPLC analyses coupled to a mass spectrometric detector revealed that the secretion contain a highly diverse mixture of macrocyclic polyamines, the polyazamacrolides (PAMLs) 47-52 (Fig. 8). 

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