Retro-mass-spectral synthesis

Mass Spectra and Retro-Mass Spectral Synthesis... 

Mass Spectra and the Retro-Mass Spectral synthesis.65... 

Hesse s excellent general introduction to alkaloid chemistry naturally contains numerous references to indole alkaloids, and in particular contains a detailed discussion of the structure elucidation of villalstonine, by way of illustration of modern experimental methods used in alkaloid chemistry.1 Indole alkaloids also receive mention in a brief review of hypotensive principles from plants,20 in a review of synthesis via photocyclization of enamides,2 and in another on the use of lactones in alkaloid synthesis.21 Kametani has also reviewed (unfortunately, in Japanese) the synthesis, by his group, of alkaloids by retro mass spectral synthesis .2d The proceedings of the 1979 meeting of the Phytochemical Society of Europe, which were entirely devoted to indole alkaloids, are now available.3... 

The Kametani group further investigated quinazolone synthesis by cycloaddition of iminoketene with imines based on the concept of retro mass spectral synthesis and applied it to the total syntheses of deoxyvasicinone (24),... 

A new and very neat synthesis of evodiamine and rutaecarpine is described by the authors as a retro mass spectral synthesis , since the original conception was derived from the mode of fragmentation of these alkaloids in the mass spectrometer this involves a familiar retro Diels-Alder fission of ring c. Evodiamine (16a) was thus constructed by a 27r + 47r cycloaddition of 3,4-dihydro-/8-carboline with the keteneimine (17), prepared in situ by elimination of sulphur dioxide from the sulphinamide anhydride (18) (Scheme 7). When the anthranilic acid derivative (19) was used the product was rutaecarpine (20) itself, the initially formed dihydro-... 

Kametani, T., 8c Fukumoto, K. 1976. "Total Synthesis of Natural Products by Retro Mass Spectral Synthesis." Accounts of Chemical Research, 9 319-325. 

Kametani et al have achieved a very neat synthesis of euxylophoricine A (20) by application of their retro-mass-spectral synthesis. Cycloaddition of 3,4-dihydro-j8-carboline with the iminoketen (21b), prepared in situ by decomposition of the sulphinamide anhydride (21a), gave euxylophoricine A (20) directly. Euxylophoricine C (22) was prepared by an exactly analogous route (Scheme 4). 

Kametani, T., T. Higa, C. V. Loc, M. Ihara, M. Koizumi, and K. Fukumoto Iminoketene Cycloaddition. 1. A Facile Synthesis of Quinazolone System by Condensation of Iminoketene with Imines — A Total Synthesis of Evodiamine and Rutaecarpine by Retro Mass-Spectral Synthesis. J. Amer. Chem. Soc. 98, 6186 (1976). 

Details of Kametani s synthesis of evodiamine and rutaecarpine by the retro mass-spectral approach22" have also been published.23" An extension of this method afforded a new synthesis23 of rutaecarpine (26) thus, condensation of the... 

In many cases, fragmentations corresponding to the retroreaction of a powerful reaction (sec. lO.S.B.vi) can be identified and used retrosynthetically. Retro-mass spectral analysis has been applied to total synthesis by Kametani. The mass spectra of tetrahydroisoquinoline alkaloids show fragmentations by the three major pathways shown in Scheme 10.24.1 Kametani observed that path c (a retro Diels-Alder reaction) was the major fragmentation pathway (sec. ll.S.B). Xylopinene (274) gave this specific fragmentation (to 275 and... 

Scheme 10.25. Synthesis of xylopinene (274) based on retro-mass spectral analysis.

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