ABSTRACT
The reaction mixture for the hydrogenation of ethyl pyruvate on Pt-alumina catalyst modified with isocinchona alkaloids (alpha-ICN (I) and beta-ICN (II)) was studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS). It was established that part of the chiral modifiers themselves are converted into ions of m/z 299, 305 and 309 in the course of chiral hydrogenation. The experimental data allowed the determination of the probable structure of the ions mentioned. According to ESI-MS/MS spectra the structure of the new cinchona alkaloids was assumed: tetrahydro-isocinchonines (III-VI), decahydro-isocinchonines (VII, VIII) and hydrogenated compounds of VII and VIII by scission of their C--N and C--O bonds (IX/1, IX/2, X). Fragmentation pathways are proposed for these new compounds.
Subject(s)
Cinchona Alkaloids/chemistry , Spectrometry, Mass, Electrospray Ionization/methods , Stereoisomerism , Molecular StructureABSTRACT
The potassium salt of E- and Z-2,3-diphenylpropenoic acids prepared in situ could be esterified efficiently in DMSO with the appropriate alkyl halides at room temperature. In this way 10 previously undescribed esters of these acids were synthesised and characterised. Excellent yields were observed for most of the E isomers and the more hindered Z esters were also obtained in good yields, far better than those obtained applying the classical acid-catalysed esterification reaction.
Subject(s)
Esters , Dimethyl Sulfoxide/chemistry , Esters/chemical synthesis , Esters/chemistry , Molecular Structure , Solvents/chemistry , StereoisomerismSubject(s)
Acetic Anhydrides/chemistry , Models, Molecular , Pyridines/chemistry , Pyruvates/chemistry , Spectrometry, Mass, Electrospray Ionization/methods , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Acetic Anhydrides/analysis , Isomerism , Models, Chemical , Pyridines/analysis , Pyruvates/analysisABSTRACT
The reactions of ethyl pyruvate with acetic anhydride and pyridine were studied by electrospray ionization mass spectrometry (ESI-MS). Ethyl 2-acetoxy-2-pyridiniumpropionate (1) (m/z 238) resulting from the reaction of the acetylpyridinium cation with ethyl pyruvate, and the adduct of ethyl 2-acetoxyacrylate with a pyridinium cation (2), bound together by non-covalent interactions (m/z 238), were identified by ESI-MS for the first time. Structures 1 and 2 cannot be distinguished, probably because one may be converted into the other and vice versa.
