Analysis of metastable defocusing spectra of lycoctonine bases having 7,8-methylenedioxy groups

The parameters of the MD spectra of the fragmentary ions of 21 lycoctonine alkaloids with 7,8-MDOGs have been investigated. On this basis, the monotypicity of the main fragmentation processes characteristic for the individual groups of compounds have been confirmed. A decrease in the number of common group characteristics of the MD spectra of the ions arising as the result of multistage breakdown processes is caused by alternative methods for their formation. This is not shown only by the doublet nature of the fragmentary ions. The results of a comparison of the MD spectra with the structures of the molecules have confirmed the hypothesis expressed previously concerning the 7,8-MDOG as the center of localization of the charge, competing with the nitrogen atom and facilitating the elimination of various substituents from the diterpene skeleton. A comparison has been made of two methods of evaluating the common nature of the fragmentation reaction: from the energies of the metastable transitions and from the relative intensities of the metastable peaks. The two methods give mutually supplementary information concerning the nature of the fragmentation processes.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 397–407, May–June, 1987.     

Reactions of lycoctonine alkaloids containing a 7,8-methylenedioxy group with Na in liquid ammonia

The reactions of 6-dehydroeldelidine and 6-dehydrodelcorine with sodium in liquid ammonia have been studied. Structures have been put forward for the compounds obtained. Features of the fragmentation of these compounds under electron impact are discussed.Abu Ali Ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 527–532, July–August, 1989.     

Reactions of lycoctonine alkaloids containing a 7,8-methylenedioxy group with Na in liquid ammonia

The reactions of 6-dehydroeldelidine and 6-dehydrodelcorine with sodium in liquid ammonia have been studied. Structures have been put forward for the compounds obtained. Features of the fragmentation of these compounds under electron impact are discussed. Abu Ali Ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 527–532, July–August, 1989.     

Features of the mass spectra of hetisine bases with an OH group at C-14

The EI mass spectra of five hetisine bases with an OH group at C-14 have been investigated. The main directions of fragmentation are initiated by the cleavage of the C-14-C-20 bond. With the aid of measurements of the elementary compositions of the molecular and fragmentary ions and of a comparison of the B/E linked-scanning and metastable defocusing spectra, the mechanism of the formation of the key fragments has been established and alternative methods for the production of certain ions have been revealed.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 82–89, January–February, 1992.     

B/E linked scanning spectra of the molecular and fragmentary ions of lycoctonine bases

The B/E linked scanning spectra of the M⁺, (M-15)⁺, and (M-OR₁)⁺ ions and those of some other series have been investigated. The characteristic nature of the individual intensities of the metastable peaks (the magnitudes A) with the same R₁ radicals for different groups of alkaloids has been shown for the spectra of the M⁺ and (M-15)⁺ ions. The reason for the quantitative differences of the B/E spectra of the (M-OH)⁺ ions from the spectra of the (M-OCH₃)⁺ and (M-OAc)⁺ ions, consisting in the influence of alternative methods of eliminating an OH radical, has been found. It has been confirmed that the values of A of analogous transitions calculated from the B/E and MD spectra are close to one another. On the other hand, the values of the energy of the metastable transitions obtained by these two methods differ from one another by two orders of magnitude.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Special Design Bureau of Analytical Instrument Construction, Scientific and Technical Branch, Academy of Sciences of the USSR, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 72–84, January–February, 1991.     

某些西佛碱类化合物的质谱重排反应

研究了十四种西佛碱类化合物的电子轰击质谱，利用碰撞诱导解离(CID)和B/E联动扫描技术，证实了特殊重排产物的离子结构及生成机理，并利用亚稳离子测定方式对这类化合物的主要离子进行了归属。     

Characteristics of the mass spectra of ecdysteroids with different numbers of -OR groups

The mass spectra of 15 phytoecdysteroids and acetyl derivatives have been compared. With a decrease in the number of -OR groups, the contribution of cleavages of the bonds of the steroid skeleton increases. 20,22-Diols are characterized by the greatest significance of fragmentation at the C-20–C-22 bond. In all the spectra, clear indications of fragmentation of the side chain at the C-22–C-23, C-23–C-24, and C-24–C-25 bonds are observed.     

Characteristics of the mass spectra of ecdysteroids with different numbers of -OR groups

The mass spectra of 15 phytoecdysteroids and acetyl derivatives have been compared. With a decrease in the number of -OR groups, the contribution of cleavages of the bonds of the steroid skeleton increases. 20,22-Diols are characterized by the greatest significance of fragmentation at the C-20–C-22 bond. In all the spectra, clear indications of fragmentation of the side chain at the C-22–C-23, C-23–C-24, and C-24–C-25 bonds are observed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 518–528, July–August, 1980.     

Features of the mass spectra of C18-diterpene alkaloids

Fragmentation under electron impact of eleven C₁₈-diterpene alkaloids with an oxygen function at C-4 has been investigated. The contributions of various modes of forming the (M - CH₃)⁺ ions have been determined. The mechanism of the appearance of the fragments (M - CH₃)⁺ and (M - OCH₃)⁺ at the expense of the methoxy groups at C-14 and C-16 has been considered. The characteristic nature of the parameters of the metastable peaks in the transitions to these daughter ions has been shown. Minor directions of the fragmentation of 3,4-epoxy- and 4-hydroxy bases have been characterized.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 95–106, January–February, 1989.     

Common substructures in groups of compounds exhibiting similar mass spectra

Summary Principal component projections of sets of mass spectra show clusters that contain compounds with common structure properties. The similarity of structures is investigated by an automatic search for large common substructures within the compounds of a cluster. Resulting spectra-structure-relationships are helpful in interpretation of spectra.     

Synthesis of 7,8-dimethoxy and 7,8-methylenedioxy isochroman-3-ones an efficient synthesis of (±) tetrahydropalmatine and (±) canadine

Efficient syntheses of the title compounds, using heteroatom directed lithiation reaction is described.     

Features of the splitting out of a methyl radical from lycoctonine alkaloids under electron impact

The mass spectra of 53 alkaloids and their derivatives are considered. It is known that the presence of a C₆(OCH₃)-C₇(OH)-C₈ (OH) grouping in C₁₉-diterpene alkaloids leads to a high intensity of the (M - 15)⁺ ions at the expense of the C₆(OCH₃) group and considerably suppresses the competing processes of forming the [M - OH (OCH₃)]⁺ ions in the alkaloids and the (M - 56)⁺ ions in the anhydroxy bases. When the above-mentioned grouping is absent, the (M - 15)⁺ ions are formed mainly by the splitting out of a H₃ from a N-ethyl group.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii. No. 4, pp. 525–536, July–August, 1985.     

Identification of unknown compounds using data bases and computer simulation of mass spectra

The possibility of identification based on the comparison of experimental electron-ionization mass spectrum of an unknown (in our case, model) compound with the mass spectra of the candidate compounds generated by the Mass Frontier software has been demonstrated by the example of three model compounds. The structural isomers of the identified substances found in the ChemExper database have been used as the candidate compounds. The candidate substances have been ranged by the degree of similarity between their simulated mass spectra and the experimental mass spectrum of the unknown compound. The mass spectra have been compared on the basis of the algorithm used in the NIST MS Search standard search system. In all three cases, the sought-after structure has been indicated as the most probable one of all the candidate structures.     

Features of the splitting out of a methyl radical from lycoctonine alkaloids under electron impact

The mass spectra of 53 alkaloids and their derivatives are considered. It is known that the presence of a C₆(OCH₃)-C₇(OH)-C₈ (OH) grouping in C₁₉-diterpene alkaloids leads to a high intensity of the (M - 15)⁺ ions at the expense of the C₆(OCH₃) group and considerably suppresses the competing processes of forming the [M - OH (OCH₃)]⁺ ions in the alkaloids and the (M - 56)⁺ ions in the anhydroxy bases. When the above-mentioned grouping is absent, the (M - 15)⁺ ions are formed mainly by the splitting out of a ?H₃ from a N-ethyl group.     

Use of the method of metastable defocusing for the analysis of the processes involved in the fragmentation of lycoctonine bases

The metastable transitions in the mass spectra of 21 lycoctonine bases have been studied by the method of metastable defocusing (MD). It has been established that as a criterion of the monotypicity of single-stage fragmentation reactions it is possible to use a linear dependence of the relative intensities of the metastable peaks (MPs) on the stability of the daughter ion. In the MD spectra of the ions formed in several stages, to characterize the generality of the breakdown reactions, in addition to the intensities of the MPs, the accurate positions of their maxima and the general shape of the curve are important.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 481–495, July–August, 1984.     

Use of the method of metastable defocusing for the analysis of the processes involved in the fragmentation of lycoctonine bases

The metastable transitions in the mass spectra of 21 lycoctonine bases have been studied by the method of metastable defocusing (MD). It has been established that as a criterion of the monotypicity of single-stage fragmentation reactions it is possible to use a linear dependence of the relative intensities of the metastable peaks (MPs) on the stability of the daughter ion. In the MD spectra of the ions formed in several stages, to characterize the generality of the breakdown reactions, in addition to the intensities of the MPs, the accurate positions of their maxima and the general shape of the curve are important.     

Mass spactra of diterpene alkaloids with the lycoctonine skeleton

Conclusions The main routes of fragmentation of diterpene alkaloids with the lycoctonine skeleton under the action of electron impact are discussed.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 6, pp. 515–519, 1969