MTAD adduct

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...

A depiction of the MTAD adduct formation is given in Scheme 4. The MTAD moiety gives characteristic peaks at m/z 165/166 [M - R - R" + H] and distinct ions representing cleavage on either side of the six-membered ring. 

Fig. 2.4. Gas chromatography-electron-impact mass spectrum of the 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) adduct of 10,12-18 2 methyl ester from a commercial conjugated linoleic acid (CLA) mixture.

Diagnostic Ions for MTAD Adducts of the Methyl Esters of CLA Positional Isomers Ranging from 7,9-18 2 to 12,14-18 2 ... 

The identities of CLA isomers derived from heat-treated vegetable oils, and isolated by silver-ion HPLC, were confirmed using MTAD adducts (75). The trans,trans isomers, 9t,llt- and 10f,12i-18 2, were major componoits. Fatty acid mixtures containing natural CLA appear not to have been analyzed as the MTAD adducts by GC-MS. It has been observed that MTAD may react with methylene-interrupted uusaturat-ed fatty acids if conditions are too harsh (73), and therefore further investigation might be warranted to assess the applicability to natural CLA samples, bearing in mind that CLA, compared with other fatty acids, is at low levels in such samples. 

In vivo, CLA can be transformed by elongation/desaturation processes into a number of metabolites, and in studies on rats fed CLA, GC-MS of specific derivatives has been used for determining their structure (79-82). DMOX derivatives, picolinyl esters, and MTAD adducts have all been used, often in a complementary manner. Before GC-MS analysis, it was necessary to fractionate the metabohtes by RP-HPLC,... 

GC-MS has been an invaluable tool for determining the positions of double bonds in CLA metabolites formed by elongation/desaturation reactions. As for CLA, DMOX derivatives and MTAD adducts have proved to be useful some-... 

For the components with a conjugated diene system, derivatization with MTAD is useful to determine the unsaturated positions [168]. Adducts of the di-enophile MTAD, which is formed with conjugated dienes via Diels-Alder cyclo-... 

While unsubstituted imidazo[l,5- ]pyridine when treated with MTAD and PTAD gives unstable 1 2 adducts, compounds 386 under the same conditions provide good yields of 387 (Equation 54) <1995JHC1525>. 

The alkenylchromone 600 when treated with PTAD in dichloromethane at room temperature affords fused tetracycle 601 in 92% yield (Equation 89) <2002J(P1)2799>. The same treatment of 3-substituted xanthones 602 with PTAD or MTAD gives the corresponding adducts 603 in nearly quantitative yields (Equation 90) <1998J(P1)1547>. Both epimers at C-12a result from a lack of diastereofacial control in the cycloaddition, a feature which is characteristic of the behavior of RTADs with 5-substituted cyclohexa-1,3-dienes <1980JOC5105>. 

Reaction of tetrasubstituted isopyrazoles 640 with PTAD or MTAD affords the corresponding adducts 641 in high yields (Equation 95) C1970JA6218, 1995JOC308, 1996JOC3172>. 

Figure 4. The mass spectrum of the adduct of methyl cis-, trans-9,11-octadecadienoate and 4-methyf-1,2,4-triazoHne-3,5-dione (MTAD). Reproduced by permission of AOCS Press (143).

Diels-Alder addition of MTAD to naphthalene (84JA5368 85MI2) and phenanthrene (88TL5509) under photochemical conditions has been described. Even irradiation of an MTAD solution in benzene at -40°C gives the corresponding Diels-Alder adduct (89JA9247). However, these adducts are thermally unstable and undergo cycloreversion at about — 10 C. 

Reaction of 1,2-diphenylcyclopropene derivatives (380) with PTAD gives bicyclic derivatives 383. Aziridine intermediate 381 is expected to rearrange to dipole 382, which then collapses to the final product (Scheme 63). Cycloaddition of MTAD to similar vinylcyclopropene 384 proceeds in a different way, providing 386. Formation of this product can be rationalized in terms of an initial formation of the Diels-Alder adduct 385, which then rearranges by a 1,3-sigmatropic shift to thermodynamically more stable compound 386 (90JOC2478). 

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