DMDS adducts

Fig.8A,B Derivatization of Type I pheromones A Z7-12 OAc with dimethyl disulfide (DMDS) and mass spectra of the DMDS adduct B E5,Z7-12 OAc with 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) and mass spectra of the MTAD adduct...

Fig. 9A,B GC-MS analysis of the pheromone extract of Anadevidia peponis (Noctuidae, 1 FE) treated with DMDS A TIC B mass chromatograms [141]. The mass chromatograms, which are multiplied by indicated factors, monitor the M+ of DMDS adducts derived from C10 to C16 monoenyl acetates (m/z 292,320,348, and 376) and some diagnostic fragment ions (m/z 89,117,145,173,175,203,231, and 259) to determine their double-bond position. Peaks I-VI indicate the DMDS adducts of the following components in the pheromone gland Z5-10 OAc (I),Z5-12 OAc (II),Z7-12 OAc (III), ll-12 OAc (IV),Z9-14 OAc (V), and Zll-16 OAc (VI)...

Example The oxidative addition of dimethyl disulfide (DMDS) transforms the double bond to its 1,2-bis-thiomethyl derivative (a). Induced by charge localization at either sulfur atom, the molecular ions of DMDS adducts are prone to a-cleavage at the former double bond position (b). This gives rise to sulfonium ions that are readily identified from the mass spectrum (Chap. 6.2.5). The method can be extended to dienes, trienes, and alkynes. [70,71] (For the mass spectral fragmentation of thioethers cf. Chap. 6.12.4). 

Figure 4.1 GC/MS analysis of methyl esters prepared from a whole cell lipid extract of the YEpOLEX-PDesat-TnD11Z-transformed ole1 strain of Saccharomyces cerevisiae (A) total ion spectrum of fatty acid methyl esters resolved by capillary GLC (B) mass spectrum of the degradation products of the DMDS adduct of Z11 -16 Me in A. The diagnostic m/z values of the DMDS adduct of Z11-16 Me are labeled. (Reproduced with permission from Knipple et al., 1998. 1998 by The National Academy of Sciences.)...

Figure 4.4 GC/MS analysis of DMDS adducts of methyl esters prepared from whole cell lipid extracts of the YEpOLEX-PoctoZIO-transformed olel strain of S. cerevisiae (A) control olel yeast cells supplemented with 0.5 mM Z11 -18 Acid (B) YEpOLEX-PoctoZl0-transformed olel yeast cells supplemented with 0.05 mM Z11-18 Acid (C) mass spectrum of DMDS adduct of Z10-16 Me in B. GC peaks prior to 25 minutes in A and B correspond to saturated C10-C18 methyl esters. Peaks corresponding to DMDS adducts are found at 44 min for externally added Z11-18 Me and at 38 min in B for Z10-16 Me. (Reproduced with permission from Hao et al., 2002. 2002 by Insect Biochemistry and Molecular Biology.)...

SCHEME 3. a) Synthesis of dimethyl disulfide (DMDS) derivatives of isolated double bonds (monounsaturated compounds or double bonds separated by four or more CH2 groups) b) DMDS adducts from dienes with double bonds separated by 1, 2, or 3 CH2 groups c) DMDS adducts from conjugated double bonds. 

Dimethyldisulfide derivatization is the most common method used for double bond position determination. Reaction of the alkene in hexane with dimethyl disulfide (DMDS) and iodine under an inert atmosphere at 60°C produces the DMDS adduct. MS fragmentation of the DMDS derivatives occurs between the methylsulfide groups, thus locating the original double bond position (Figure 7). DMDS derivatization was used for the determination of the double bond position in (E)-8-dodecenyl acetate, the sex pheromone of the citrus fruit borer. 

When a sufficient amount of sample is available (ca. 1 pg), monoenyl compounds can be analyzed by micro-ozonolysis with and without a solvent [146, 165]. Ozonides, directly injected into GC-MS, are reductively decomposed into two aldehydes by heat. Besides this chemical reaction, the double-bond position is easily and high-sensitively confirmed by making an adduct with DMDS, which... 

In this latter study, the position of the isolated double bond in the chains was established by DMDS treatment, followed by linked scan MS/MS analysis of the resulting mixture of adducts [136]. As in the case of the European species, there are always three position isomers of the isolated double bond for each chain length. Moreover, the positions of this double bond are always the same with... 

The mechanism of the N03 radical reaction with DMDS is complex. The rate constants for the N03 reaction with CH3SCH3, CH3SH, and CH3SSCH3 (Table 8.17) are similar and much larger than that for the reaction with H2S. This suggests that by analogy with the dimethyl sulfide reaction, the initial step is addition to a sulfur atom to form an adduct that then reacts further ... 

FTIR studies of the N03-DMDS reaction (Jensen et al., 1992 MacLeod et al., 1986) identified HCHO, S02, CH30N02, CH3S03H, HN03, and CH3SN02 as products of the reaction with N03. In addition, there were a number of FTIR bands that were unidentified. Presumably the decomposition of the adduct gives at least in part intermediates such as CH3S and CH3SO, which then go on to react as described earlier (see Fig. 8.25). 

Adam, W., Makosza, M., Stalinski, K., Zhao, C.-G. DMD Oxidation of in-Situ-Generated sH Adducts Derived from Nitroarenes and the Carbanion of 2-Phenylpropionitrile to Phenols The First Direct Substitution of a Nitro by a Hydroxy Group. J. Org. Chem. 1998, 63, 4390-4391. 

Janies LP, Lamps LW, McCullough S, Hinson JA (2003a) Interleukin 6 and hepatocyte regeneration in acetaminophen toxicity in the mouse. Biochem Biophys Res Commun 309 857-863 James LP, Letzig L, Simpson PM, Capparelli E, Roberts DW, Hinson JA, Davem TJ, Lee WM (2009) Pharmacokinetics of acetaminophen-protein adducts in adults with acetaminophen ovtadose and acute liver failure. Drag Metab Dispos 37 1779-1784. Published online May 13, 2009 10.1124/dmd.l08.026195... 

DMDS derivatization was extended to diunsaturated fatty compounds by Vin-centi et al. (27). Only when the two double bonds in dienes are separated by at least foiu methylene groups do the expected di-adducts arise (27). When the two double... 

The synthesis of fluoroalkyl-substituted heterocycles is a subject of continuous interest this challenging issue has been presented in details in reviews [107,108]. It has been shown that trifluoromethyl carbanion, generated from (trifluoromethyl) trimethylsilane (the Ruppert reagent), adds easily to 2-chloro-3-nitropyridine. The produced o adducts can be oxidized with dimethyldioxirane (DMD) to form two isomeric 2-chloro-4-(and 6-)trifluoromethyl-3-hydroxypyridines (Scheme 30) [109]. 

These results indicate that DMD directs its action on the negatively charged nitro group of the a -adducts to form intermediate cyclohexadienone and subsequent aromatization. Sensitivity of KMnO oxidation of the a -adducts to the steric effects at the addition site and high value of kinetic isotope effect (KIE) k lk 10 at -70°C [12b] suggests that the oxidation proceeds via direct interaction of the oxidant with the oxidized site, hence probably via abstraction of the hydride anion. 

The ONSH in nitroarenes with carbanions carried out at low temperature and KMnO in liquid ammonia or DDQ and DMD in THF/DMF is a general process. For instance, this reaction has found valuable application for introduction of nitroaryl and hydroxyaryl substituents into molecules of a-amino acids. Thus, carbanions of esters of protected amino acids upon addition to nitroarenes form o -adducts that are oxidized by KMnO in liquid ammonia or DDQ in THF/ DMF. The subsequent hydrolysis produces a-nitroaryl a-amino acids (Scheme 11.7) [15]. 

Oxidation of these a -adducts with DMD results in an introduction of />-hydroxyaryl substituents into a-positions of amino acids [15]. The formation of a -adducts is connected with creation of a stereogenic center. When the carbanions of protected amino acids contain a chiral center in the vicinity of the prochiral carbanion moiety, the formation of the o"-adducts proceeds with high stereoselectivity. Since the oxidation of the a -adducts does not affect the newly formed stereogenic center, the ONSH in such cases proceeds with high diastereoselectivity and, as a consequence, enantioselectivity (Scheme 11.8) [16]. 

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