Mass spectra of steroidal

T.R. Sharp, M. Sutton, A. Ferguson and K.N. Marsh, Electron impact mass spectra of steroids Androstanes and derivatives. Presented at the 37th ASMS Conference on Mass Spectrometry and Allied Topics, Miami Beach, FL, 21-26 May 1989. 

Fig. 8.21. FAB mass spectra of steroids separated by CEC. Column, 350 x 0.05 mm i.d. packed with 3 pm Hypersil ODS eluent, 4 mmol/1 sodium tetraborate, 80% acetonitrile applied voltage, 21.5 kV detection, CFFAB-MS, 230-500 amu matrix, post column addition of 1% glycerol in 50% water-50% methanol, 5 pl/min sample, testosterone ([M+H]+ 209), hydrocortisone ([M+H]+ 363), aldosterone ([M+H]+ 361) (in order of elution). (Reproduced from ref. [25] with permission of John Wiley Sons).

Several texts and reviews covering various aspects of steroidal alkaloids are available. Amongst these are "Chemistry of the Alkaloids," ed. S. W. Pelletier, Chapter 19 (by Y. Sato), van Nostrand Reinhold, New York, 1970 D. R. Dalton, "The Alkaloids," Part 7, Chapters 37 and 41, Marcel Dekker, New York, 1979 "The Alkaloids Chemistry and Physiology," ed, R. G. A. Rodrigo, Vol. 19, Chapter 2 (by H. Ripperger and K. Schreiber), Academic Press, New York, 1981. Periodic reviews are to be found in Specialist Periodical Reports, Vols. 8-13, and Natural Product Reports, Vol. 1, 1984 (Royal Society of Chemistry, London). Numerous recently-isolated steroidal bases are listed in J. S. Glasby, "Encyclopaedia of the Alkaloids," Vol. 4, Plenum Press, New York and London, 1983. The mass spectra of steroidal alkaloids have been reviewed (H. Budzikiewicz, Mass Spec. Rev., 1982, 1, 125,... 

Table 11 compares some preprocessing methods for mass spectra of steroids C2513. Normal spectra and spectra normalized to local ion current show the best classification- These results are valid only for a certain classification procedure and only for steroid mass spectra-Nevertheless, qualitative conclusions may be drawn also for other methods or other types of compounds-... 

Mixtures of NO/N2 (2-15%) were shown to enhance the M ion in the mass spectra of steroidal alcohols and the trimethylsilyl-ethers of biologically-important polyols and glucuronides (48). 

The correlation between the electron impact mass spectra of steroids and their structure has been a well-researched topic over the last twenty years. The success of mass spectrometry in this area owes much to the detailed analyses by Djerassi and co-workers. For unconjugated steroids, EIMS has been able to answer many structural questions. 

In view of our results obtained in reactions of the tetrahalogeno-benzynes with aromatic compounds we carried out a reaction of tetra-fluorobenzyne with the A-ring aromatic steroid 3,l7,fl-dimethoxy-oestra-l(10),2,4-triene (119) 154>. As we expected the initially formed enol-ethers were very rapidly hydrolysed and the adducts were isolated as the ketones (120) and (121). The mass spectra of the compounds (120) and (121) did not show molecular ion peaks and as anticipated the ketones were rapidly converted into the naphthalenes (122) and (123) photo-chemically. 

The RDA reaction is often observed from steroid molecular ions, and it can be very indicative of steroidal stmcture. [107,110,113,114] The extent of the RDA reaction depends on whether the central ring junction is cis or trans. The mass spectra of A -steroidal olefins, for example, showed a marked dependence upon the stereochemistry of the A/B ring juncture, in accordance with orbital symmetry rules for a thermal concerted process. In the trans isomer the RDA is much reduced as compared to the cis isomer. The effect was shown to increase at 12 eV, and as typical for a rearrangement, the RDA reaction became more pronounced, whereas simple cleavages almost vanished. This represented the first example of such apparent symmetry control in olefinic hydrocarbons. [114]. 

Longevialle, P. Better, R. Electron Impact Mass Spectra of Bifunctional Steroids. The Interaction Between Ionic and Neutral Fragments Derived From die Same Parent Ion. Org. Mass Spectrom. 1983,18, 1-8. 

Amino Acids Detection of the molecular ion peaks of amino acids can be difficult. If we examine the mass spectra of amino acids, as well as of steroids and triglycerides, by a variety of ionization techniques, we can appreciate their relative merits. 

Mass spectra of methoxime (MO)-TMS derivatives of steroids typically give the following fragments M-31 (loss of oxime), sequential 90 losses (trimethylsilanol), loss of the primary TMS group (M-103), and combinations thereof. Often the ion chosen for monitoring is one formed by the above fragmentations. A detailed de-... 

Transform Mass Spectrometry Mass Spectra of Glycoalkaloids and Steroid Glycosides," Biomed. and Env. Mass Spectrom., 13, 19-204 (1986). 

The gas-chromatographic separation of corticosteroids as cyclic boronates offers considerable promise. Alkyl (or phenyl) boronic acids condense readily with 17a,20-, or 20,21-diols, and also with 17a,21-hydroxy-20-oxo steroids to form cyclic esters [e.g. (557) and (558)] with excellent g.l.c. properties. The mass spectra of these boronates exhibit prominent molecular ions. 

The mass spectra of 1-amino-steroids are not affected by the. configuration of the amino-group. H-D exchange reactions observed with deuteriated amines were explained by the high activation energy of the last fragmentation leading to the main ion. The relative importance of M-43 ions in the mass spectra of the 1-methylamino-compounds was explained by a conformational effect. 

Mass spectra of a series of 20-pyridyl steroids were measured, and the fragmentations discussed. Intramolecular hydrogen transfer in mass spectra rearrangements involving the loss of small neutral molecules has been reviewed.The loss of water and ammonia from hydroxy-amino- and amino-steroids was quoted. 

Figure 52. Conventional mass spectra of 14 (and 14a) keto and diketo steroids [205].

The localisation of hydroxy-groups from study of mass spectra of the derived ketones has been described. 5a- and 5 -3-oxo-steroids can generally be distinguished by their characteristic fragmentations. The same compounds can be converted into their enol trimethylsilyl ethers, having the olefinic bond respectively in the A - and A -positions. Each affords a distinctive mass spectral fragmentation pattern. ... 

C. Mass and N.M.R. Spectra of Steroidal Amines.—A study has recently been made18 of the mass spectral fragmentation pattern of the dimer (28), obtained by reduction of the cyanamide of conanine with lithium aluminium hydride.19 As with certain benzylamines, a major fragment has been interpreted to arise from a heterolytic rupture of the C—N= bond. 

For one, the mass spectra of trimethylsilyl derivatives may not be suitably informative. Frequently, the intensities of molecular-ion and useful fragment peaks are low compared with those of the ubiquitous MejSi m/e = 13), MejSiOH (m/e = 15), and MejSiOSiMej" (w/e = 147) peaks, obscuring clues as to the identity of low concentration components. Polyhydroxy compounds, such as certain steroids, tend to undergo fragmentation by successive losses of trimethylsilanol (MejSiOH) molecules, exhibiting series of peaks 90 mass units apart, with attendant uncertainty as to whether the molecular-ion peak is the highest-mass member of the series or something invisible beyond that. 

C. Mass and N.M.R. Spectra of Steroidal Amines.—The fragmentation pattern in the mass spectrometer of steroidal diamines has been reported. 

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