Sodium adducts

Isoquinoline can be reduced quantitatively over platinum in acidic media to a mixture of i j -decahydroisoquinoline [2744-08-3] and /n j -decahydroisoquinoline [2744-09-4] (32). Hydrogenation with platinum oxide in strong acid, but under mild conditions, selectively reduces the benzene ring and leads to a 90% yield of 5,6,7,8-tetrahydroisoquinoline [36556-06-6] (32,33). Sodium hydride, in dipolar aprotic solvents like hexamethylphosphoric triamide, reduces isoquinoline in quantitative yield to the sodium adduct [81045-34-3] (25) (152). The adduct reacts with acid chlorides or anhydrides to give N-acyl derivatives which are converted to 4-substituted 1,2-dihydroisoquinolines. Sodium borohydride and carboxylic acids combine to provide a one-step reduction—alkylation (35). Sodium cyanoborohydride reduces isoquinoline under similar conditions without N-alkylation to give... 

Because carotenes lack heteroatoms such as oxygen to which protons or sodium cations might attach, no ions are usually detected for these hydrocarbon compounds during ESI in positive mode, although protonated molecules and sodium adducts were observed for xanthophyUs under normal conditions with MeOH, MTBE, and H2O as a mobile phase from HPLC. Addition of a heptafluorobutanol oxidant at 0.1 or 0.5% produced abundant molecular ions of p-carotene with high reproducibility. Substitution of MeOH for acetonitrile produced similar limits of detection. ... 

Our attempts to isolate larger amounts of 6 from the solution have failed so far. The mass peak of the sodium adduct of 8 (Mg Na+ = 246.8), however, strongly supports the oxidation of 5 into 6 as a prerequisite for the subsequent formation of 8 from 7 as outlined (eqs. 6 and 7). The addition of ethylamine to capture the reactive aldehyde 6 as imine did not result in recognized reaction products. 

Analytical methods for the detection of residues of semicarbazide use derivatisation with 2-nitrobenzaldehyde and LC-MS detection. Figure 18 shows the positive ESI response for a 1 ppm solution of semicarbazide after derivatisation and concentration. The main peak 2 at 16 min shows the expected 209 (M+H)+ ion of the 2-nitrobenzaldehyde derivative of semicarbazide together with its sodium adduct ion at m/z 231 (Figure 19). 

CID spectra obtained for the metabolite with mh 413 was similar to that of the previously discussed metabolite mlz 383). At high collision energy the fragments with mh 229.0870 (Ci4H1303), mh 151 and mh 105 that presumably correspond to BP3 and its main fragments were also detected. In the spectrum obtained at low collision energy, apart from the sodium adduct of BP3 mh = 251.0694,... 

Figure 5.2 GALDI mass spectra of (a) fresh hydroxydammarenone (1, sodium adduct [M+Na]+ at m/z 465) and (b) an equimolar mixture of hydroxydammarenone (1 H, m/z 465), uvaol (5 U, m/z 465), oleanonic acid (3 On, m/z 477), oleanolic acid (2 Ol, m/z 479), andglycyrrhetinic acid (4 G, m/z 493) [39]. In (a), a small amount of (M+16) is visible at m/z 481 in the unaged sample. Signals marked with crosses at m/z 413, 469, 483, and 507are contaminants in the spectrometer...

Table 5.1 Components of fresh dammar resin, as reported in the literature [34] with corresponding m/z values of the sodium adducts (see Figure 5.6a)...

The time-of-flight mass spectrometer was usually operated in the positive mode in order to detect the cationic sodium adducts of the analyte molecules. The anions of H-acidic substances were detected in the negative mode. This mode significantly enhanced the signals of acidic compounds, e.g. free fatty acids compared with ester signals in the mass spectra of beeswax and tung oil. 

Table 5.5 Prominent peaks in the mass spectrum of aloe resin (see Figure 5.13), interpretation following the literature. The dyes are not detected as sodium adducts but as radical cations formed by direct absorption and ionisation of the laser energy...

NPEOs and OPEOs (rcEo = 3-10) as industrial blends or standard compound (Triton X-100), respectively, were separated together with linear alkylbenzene sulfonates (LASs) on a Ci-RP column [10]. The intensive ions that could be observed in the spectra were mono-, di- and tri-sodium adduct ions [M + Na]+ (m/z 581), [M + 2Na]+ (m/z 604) and [M + 3Na]+ (m/z 626) of the EO7 homologue. The intensity of the molecular [M + H]+-ion, however, was small compared with the sodium adduct ions. The compounds had been concentrated prior to separation on Cis and SAX SPE cartridges. Samples from river water were handled in the same way. 

Using the same instrument with an ESI interface NPEOs and OPEOs show a great affinity for alkali metal ions. They gave exclusively, evenly spaced sodium adducts [M + Na]+, due to the ubiquity of sodium in the solvents and surfaces (Fig. 4.3.1(B)). In another type of instrument applying ESI, however, a relatively complicated spectrum was obtained (Fig. 4.3.2(A)), with similarities to the APCI spectrum of the first instrument. 

Although sodium adducts were preferably formed in both instruments, even in the absence of added electrolyte, in order to avoid the possible reduction in ionisation due to insufficient concentration of metal ions in solution, it is recommended that sample extracts are fortified with sodium ions prior to injection. However, the addition of higher concentrations can induce system instability and analyte suppression. Therefore, the concentration of added electrolyte should... 

Shang et al. [7] studied the effect of different additives (NaAc, NaOH, NaCl, NH4Ac) on analyte signal intensity and they found that the relative intensity of NPEO adduct ions may be enhanced by all additives, but NaAc produced the most abundant adduct ions for the entire ethoxylate series with good reproducibility. Additionally, the intensity of adducts, especially for mono- and diethoxylates was found to depend on reaction time prior to LC-ESI-MS analysis and concentration of NaAc. They recommended 0.5 mM NaAc for normal-phase separation with solvent system toluene-MeOH-water. In reversed-phase systems the highest abundance of sodium adducts for NPEOs ( iEO = 1-10) was observed at concentrations higher than 10 xM, while any further increase in concentration had very low influence on signal intensity [10,11],... 

Adducts have also been obtained by the reaction of methylmagnesium iodide with 3,5-dicyanopyridine and related substrates.138 Their formation involves a shift in the IR spectrum from 1563-1575 cm 1 to 1612-1645 cm"1, for C=C bonds, and from 2230-2248 cm 1 to 2125-2225 cm for the C=N bond, the final values being near the absorbance of the dihydro derivatives. Hydrolysis yields the expected dihydro derivatives. In connection with the nature of metal-nitrogen bond, it is of interest that in the sodium adduct 94 the IR spectrum indicates appreciable electron delocalization relative to the corresponding dihydro derivative (shift toward lower frequency), which suggests a substantial ionic character of the bond due to the low electronegativity of sodium. 

The negative charge distribution in the adducts was evaluated on the basis of the chemical shift values and found to be nearly 75% concentrated on the nitrogen atom. In the reactions of l-ethoxycarbonyl-l,4-dihydropyridines with organosodium and organopotassium compounds, the resulting metal-associated (j-adducts were not soluble in aliphatic hydrocarbons alone but were made so by addition of 18-crown-6. This behavior would support ionic structures for the potassium and sodium adducts. 

Sodium chloride may be added to the eluting solvent at a concentration of 0.01 M in order to accentuate sodium adduct ions in the MALDI-TOF mass spectrum and suppress the formation of potassium adduct ions. 

Figure 2 Oligonucleotide artifacts detectable on MALDI-TOF MS. The spectrum shows a typical example of an oligonucleotide of poor quality. The presence of a sodium adduct peak is depicted (Na adduct) and evidence of depurination potentially at G nucleobases (Depurinated). The oligonucleotide sequence used was 5 OH-TAGGCCTGGGAAGCAGCA-OH 3. ...

This analysis revealed a set of ions that were strongly elevated in the IDH mutant-containing cell lines. The exact mass identified these ions as (R)-2-hydroxyglutarate (2HG), the sodium adduct of 2-HG, and the dehydrated product of 2-HG. In vitro experiments with recombinant IDH confirmed that the mutant enzyme, but not the wild-type enzyme, is able to produce 2-HG (Fig. 9). Finally, this correlation was demonstrated to be of clinical relevance because patients with mutated IDH had higher levels of 2-HG. This example highlights the utility of metabolomics in the characterization of enzyme-substrate interactions, in this case a mutated enzyme associated with cancer. Moreover, this work has opened up a new field dedicated towards understanding if and how this IDH mutation leads to cancer [31, 56, 57]. 

MALDI-TOF mass measurement of the ball-type Pcs is the most powerful technique in order to determine their molecular weight and to characterize their structures. In this technique, it is important to find the appropriate matrix in order to obtain highly resolved spectra, thereby obtaining good mass resolution. If we take into account the MALDI-TOF-MS of the ball-type Pcs 33, 34, 35, and 36 in Fig. 9 [46] and 39 and 40 in Fig. 10 [47] as examples, the protonated molecular ion peaks of 33 and 34 were observed at low intensity, but the sodium adduct peaks of Pcs 33 and 34 were found to be dominant, intense peaks in the linear-mode MALDI-TOF-MS by using... 

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