Isolation high resolution mass spectrometry

B Nicotine is a diamino compound isolated from dried tobacco leaves. Nicotine has two rings and M + = 162.1157 by high-resolution mass spectrometry. Give a molecular formula for nicotine, and calculate the number of double bonds. 

A systematic investigation of the free amino acids of the Leguminosae led to the isolation of a novel ninhydrin-positive compound from the leaves of Derris elliptica Benth. (Papilionidae) (93). This substance was analyzed as C6H,3N04 (microanalysis and high resolution mass spectrometry) and was shown to be an amino alcohol. The absence of a carbonyl in the 1R, the loss of 31 mass units in the mass spectrum, and a positive periodate cleavage reaction were best embodied into a dihydroxydihydroxymethylpyrrolidine structure. The relative simplicity of the NMR spectra (three peaks in the 13C spectrum four spin-system in the H spectrum) pointed out a symmetrical structure. Inasmuch as the material was optically active ([a]D 56.4, c = 7, H20), meso structures were ruled out, and the 2R, 3R, 4R, 5R relative configuration was retained (93). This structure (53) was further confirmed by an X-ray determination (94). 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

Complete structure elucidation of individual resin glycoside constituents is now achieved readily by the use of a combination of high-resolution mass spectrometry and NMR spectroscopy. These methods are applicable to the isolated natural products or to their peracetylated and methylated derivatives. 

A number of new 14-membered-ring alkaloids incorporating the p-hydroxy-styrylamine and j8-hydroxyphenylalanine structural features have been isolated and structurally elucidated, mainly by application of high-resolution mass spectrometry. Cre natine A (55) has been obtained from Discaria crenata while alkaloid A, (feretine) (56) and alkaloid A2 (57) have been isolated from Feretia apondanthera. In addition to four known alkaloids, the root bark of Zizyphus nummularia has yielded nummularine-D (58) and nummularine-E (59). ... 

All of the calystegines isolated to date have been obtained as amorphous white solids and melting points have therefore not been reported. Structures have been determined by spectroscopic methods, in particular H and 1SC NMR spectroscopy and high-resolution mass spectrometry. Additional confirmatory evidence has been obtained from analysis of the alkaloids as trimethylsilyl ether derivatives by gas chromatography - mass spectrometry (Section 4.4). In certain cases the structures and absolute configurations have been confirmed by synthesis (Section 6). 

Some of the most difficult structural problems in the indole alkaloid field are associated with the bisindole alkaloids of the vobtusine type. Since 1955, vobtusine has been isolated on numerous occasions, often in large quantities, from the Apocynaceae species Callichilia, Conopharyngia, Rejoua, and Voacanga A correct molecular formula could only be determined by high-resolution mass spectrometry. In 1966 a partial structure was proposed for the alkaloid and later in the same year a complete structure was put forward. An unambiguous structural proof is, however, still lacking. The difficulty arises from the complete resistance of the alkaloid and its derivatives to cleavage, in contrast, for example, to the dimers of the voacamine and vinblastine types. Non-cleavable dimers occur also in calabash-curare but in these cases chemical correlation with cleavable alkaloids has been possible (see Section 2, p. 209). To date no bisindole alkaloid related to vobtusine has been found which can be split into monomeric units. 

Dehydrocancentrine-B, a cherry-red alkaloid isolated from the same source, had the same functional groups as cancentrine (NMR, IR). However, its IR spectrum indicated the presence of an additional double bond in agreement with the molecular formula (C36H32N2O7) obtained by high-resolution mass spectrometry (HRMS). The mass spectrum was very similar to that of cancentrine with the exception that ions from the cularine half of the molecule appeared two mass units lower. Thus there were ions at m/e 361 (C21H15NO5) and m/e 348 (C20H14NO5) arising from fissions a + b and a -l- c, respectively (Scheme 1). This indicated that the extra double bond was in the cularine part of the molecule and must be located at the only available position, namely, C-31—C-32 (12). The NMR spectrum supported the location of the double bond in this position by the presence of a fourth AB system one half of which was visible at S 6.25 (Jab = 7.0 Hz). The location of the substituents and the relative stereochemistry of the alkaloid were shown to be identical with those... 

The oligostilbenoid vaticaffinol (15) was isolated initially from Vatica affmis [57]. High-resolution mass spectrometry on the molecular ion was unsuccessful for this compound, but its decamethyl ether showed a molecular ion at m/z 1056.4253 (C66H62O12). Its UV absorption maximum was observed at 282 nm (EtOH, log G 4.4) [48], and the IR spectrum showed prominent hydroxyl group absorption at 3200 cm-. TTie 3C-NMR spectrum of vaticaffinol (15) at 75 MHz displayed 56 carbons, and the H-NMR spectrum at 270 and 300 MHz showed six aliphatic protons... 

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