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.     

Mass spectrometry of sesquiterpenoids of the carotane series. Influence of various methods of ionization on the fragmentation of sesquiterpenols

The mass spectra of five natural sesquiterpenols with various methods of ionization have been studied. A distinct direction of breakdown according to the alternative positions of the OH group at the C-4 or C-5 atom for the skeleton has been found. It has been established that the use of chemical ionization and of secondary-ion mass spectrometry raises the intensity of the molecular ions and increases specific directions of fragmentation.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 522–525, July–August, 1993.     

Mass spectra of diterpene alkaloids with the hetisine skeleton

An analysis of literature material has shown that the stability of the M⁺ ions of bases with the hetisine skeleton decreases considerably when an OR group is present at C-1, C-6, or C-9. The directions of fragmentation are not monotypical and depend greatly on the positions of the oxygen substituents. A similar conclusion can be made from a study of the group and individual features of the breakdown of hetisine, nominine, talatisine, and their derivatives revealed with the aid of high-resolution mass spectrometry and MD spectra. An unusual property of these spectra is the formation of nitrogen-free fragments. The mass spectra of hetisine alkaloids of a new type — zeraconine and its N-oxide — have been characterized.Institute of the Chemistry of Plant Substances of the Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 542–553, July–August, 1987.     

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.     

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.     

Features of the mass spectra of lycoctonine bases with 7,8-methylenedioxy groups

The mass-spectral properties of 21 lycoctonine bases with 1-methyoxy-7,8-methyl-enedioxy groups have been studied and generalized. An influence of a methyl-enedioxy group of the nature of the substituents at C-6 and C-10, and of a ¹⁰⁽¹²⁾ bond on the fragmentation of the alkaloids and their derivatives has been found.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Abu Ali ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 389–397, May–June, 1987.     

Mass spectra of pseudoguaianolides related to carpesiolin

The main directions of fragmentation and the EI of six pseudoguaianolides related to carpesiolin have been studied. It has been established that acylation of the OH group at C-6 suppresses the selective breakdown of the guaiane skeleton, while the simultaneous presence of AcO groups at C-2 and C-4 favors the formation of a number of characteristic ions. The hydrogenation of the exomethylene group has no appreciable influence on direction of fragmentation. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 530–535, July–August, 1993.     

Mass spectrum of glycosides of ecdysteroids and their peracetates

Features of the fragmentation of the carbohydrate chains of galactopyranosides of ecdysteroids (sileneosides A–D) and their peracetates under electron impact are discussed. The migration of Gal and AcGal residues from C-22 to C-20 has been detected. The secondary-ion mass spectra of the sileneosides using liquid matrices are considered.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. All-Union Scientific-Research Institute of Agricultural Biotechnology, V. I. Lenin All-Union Academy of Agricultural Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 226–231, March–April, 1991.     

Oximes and nitriles of cardenolides

The influence of the oximation of cardenolides and the production of 10-cyanocardenolides on their biological activity has been studied. The prefered conformation of strophanthidin 19-aldoxime has been established; it has chelate fragment as the result of the orientation in the same direction of the nitrogen atom of the oxime group and the hydroxy groups at C-3 and C-5.All-Union Scientific-Research Institute of the Chemistry and Technology of Drugs, Khar'kov. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 608–612, September–October, 1983.     

Mass spectrometry of pennogenin glycosides

The electron-impact mass spectra of five unesterified pennogenin glycosides, which contain the M⁺ or (M - H₂O)⁺ peaks, have been obtained. The characteristic features of the fragmentation of these compounds have been studied. In addition to ions characterizing the successive elimination of carbohydrate units, fragments have been detected which show the breakdown of the terminal pyranose ring. Five new directions of the fragmentation of the spirostanol skeleton due to the presence of an OH group at C-17 have been found.Institute of the Chemistry of Plant Substance, Academy of Sciences of the Uzbek SSR, Tashkent. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Science Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–341, May–June, 1986.     

A mass spectrometric study of some triterpenes of the dammarane series

Summary 1. The mass spectra of tetracyclic triterpenes of the dammarane series with substituents at C-3, 6, and 12 and with side chains of various structures have been studied.2. The main direction of fragmentation is the formation of ions as the result of the decomposition of the side chain and of ring C, the second type of fragmentation being controlled by the structure of the side chain.Institute of Biologically Active Substances of the Far-Eastern Scientific Center of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 286–294, May–June, 1971.     

Molecular conformations at the cellulose–water interface

¹³C-NMR chemical shifts were measured for C-4 and C-6 in a collection of eight crystalline glucoses and glucosides. The influence of the hydroxymethyl conformation was greater at C-4 than at C-6, with mean chemical shifts for gauche–trans molecules displaced 3.1 ppm (C-4) and 2.5 ppm (C-6) relative to gauche–gauche molecules. This information was used to interpret ¹³C-NMR spectra of crystalline celluloses. Chemical shifts for C-4 in the crystallite cores of celluloses I and II differed by just 0.2 ppm, but the corresponding chemical shifts for well-ordered crystallite surfaces differed by 3.0 ppm. The separation between crystallite-surface signals was attributed to different hydroxymethyl conformations at the cellulose–water interface, i.e., gauche–gauche and gauche–trans on crystallites of cellulose I and cellulose II, respectively. A broad C-4 signal in the spectrum of cellulose II indicated gauche–gauche conformations in disordered cellulose. Chemical shifts for C-6 were consistent with these conformations.     

Interaction of cardenolides of the strophanthidin series with functionally important sections of transport Na,K-ATPase

On the basis of an analysis of the structure-activity interrelationship of cardiac glycosides and their analogs, four-center model of the binding of the compounds with Na,K-ATPase has been proposed. These centers are represented by the steroid nucleus with a polar group at C-3 and a hydroxy group at C-14, and also by a lactone ring with a double bond. It has been shown that the hydrophobic binding section of the glycoside must be in contact with a hydrophobic region of the enzyme having a fairly large volume.Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 339–345, May–June, 1983.     

Berberis Alkaloids XXXVIII. Turcamine — A new isoquinoline alkaloid fromBerberis turcomanica

The new isoquinoline alkaloid turcamine (1) has been isolated from the leaves ofBerberis turcomanica, and its structure has been established as 8-hydroxy-7-methoxy-2-methyltetrahydroisoquinoline. A relationship has been found between a substituent at C-8 and the multiplicities of the signals from C-5 and C-6.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 894–896, November–December, 1996. Original article submitted April 15, 1996.     

Migration of the exocyclic double bond in terpenoid coumarins of the iresane series

In terpenoid coumarins of the iresane series with an exocyclic double bond, migration of the double bond into the ring with the retention of the configuration of the substituent in position 1 is observed in an acid medium. The reaction has been performed in CF₃COOH and has been monitored by the PMR method. Badrakemin has yielded conferol, badrakemone has yielded conferone, badrakemin acetate has yielded conferol acetate, colladonin has yielded moschatol, and farnesiferol A and gummosin have yielded the corresponding isomers with endocyclic double bonds. The rate of the reaction is affected by the nature of the substituent at C-6. The presence of a keto group increases the time of isomerization to 1.5 h as compared with the 5–10 min for compounds with an OH group at C-6. The increase in the time of the reaction leads to the formation of byproducts. The reaction does not take place in CH₃COOH.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 630–637, September–October, 1979.     

NMR studies of 4(3H)-quinazolinones and 4(3H)-quinazolinethiones

Summary Unambiguous¹H and¹³C NMR assignments for 4(3H)-quinazolinones1–6 and their corresponding 4-thiones7–12 have been made. This resulted in the revision of the previous assignments for the two benzenoid carbons (C-5 and C-8) of quinazolinones1,2,4, and5. Thionation of the nucleophilic amides1–6 has been found to cause a distinct change in the¹³C chemical shift of particularly C-4, but also of those of C-4a, C-5, and C-8a. One-bond and several long range heteronuclear coupling constants for the compounds have also been measured.

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Kernresonanzspektroskopie von 4(3H)-Chinazolinonen und 4(3H)-Chinazolinthionen

Zusammenfassung Die¹H- und¹³C-NMR-Spektren der 4(3H)-Chinazolinone1–6 und ihrer entsprechenden 4-Thione7–12 wurden zugeordnet. Dabei zeigte sich, daß eine frühere Zuordnung der beiden benzoiden Kohlenstoffe (C-5 und C-8) der Chinazolinone1,2,4 und5 falsch war. Ersatz des Sauerstoffs durch Schwefel in den nukleophilen Amiden1–6 führt insbesondere für C-4, aber auch für C-4a, C-5 und C-8a zu einer deutlichen Änderung der chemischen Verschiebung. Heteronukleare Kopplungskonstanten über eine und über mehrere Bindungen wurden bestimmt.

     

Mass spectrometry of sesquiterpenoids of the carotane series. Influence of various methods of ionization on the fragmentation of sesquiterpenols

The mass spectra of five natural sesquiterpenols with various methods of ionization have been studied. A distinct direction of breakdown according to the alternative positions of the OH group at the C-4 or C-5 atom for the skeleton has been found. It has been established that the use of chemical ionization and of secondary-ion mass spectrometry raises the intensity of the molecular ions and increases specific directions of fragmentation. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 522–525, July–August, 1993.     

Study on fragmentation behavior of 5/7/6-type taxoids by tandem mass spectrometry

The mass spectrometric behaviors of seven compounds, namely four 4beta(20),5-oxetane 5/7/6-type taxoids (i.e. taxayuntin A, taxayuntin B, taxayuntin and taxayuntin C) and three 4(20)-methylene 5/7/6-type taxoids (i.e. brevifoliol, taxchinin A and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol) have been investigated by the positive ion FAB-MS/MS technique. The fragmentation has been correlated with the types and positions of substituents of these compounds. It has been found that with the OH group at the C-10 position, taxayuntin A, taxayuntin B and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol are dominated by the loss of H2O, while with the BzO group at the C-10 position, taxayuntin, taxayuntin C, brevifoliol and taxchinin A preferentially eliminate the BzO group. In addition, C-2 is an active site, and neutral loss from the C-2 position readily occurs. The four 4beta(20),5-oxetane 5/7/6-type taxoids produce the terminal product ion with a stable conjugated system at m/z 311, while the 4(20)-methylene 5/7/6-type taxoids brevifoliol and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol produce this ion at m/z 237, and taxchinin A at m/z 253. Interestingly, characteristic fragment ions involving the loss of a 118 u group were observed for taxayuntin, and a possible fragmentation mechanism is given. The major fragmentation pathways and mechanisms of ion formation for the compounds are proposed on the basis of CID spectra and accurate mass measurements. The results of this paper will be helpful for structural analysis of analogs.     

Mass spectra of substituted Δ2-1,2,4-oxadiazolines—I

The electron impact fragmentation of four Δ²-1,2,4-oxadiazolines with substituents at positions 3 and 5 has been examined. The direct analysis of daughter ions and high resolution mass measurements provided valuable information regarding certain ions. The present study clearly demonstrates that the substitution of phenyl or a substituted phenyl group for alkyl at C-3 and alkyl in place of a phenyl substituent at C-5 in the oxadiazoline system alters the fragmentation modes considerably.     

Mass spectra of 3-arylidene-1H-2,3-dihydro-1,4-benzodiazepin-2-ones

The scheme of the fragmentation of arylidene derivatives of 5-phenyl-1,4-benzodiazepin-2-ones was established by means of high-resolution mass spectrometry. One of the principal fragmentation pathways of these compounds is cleavage of the 2C-3C and 4N-5C bonds to give two fragments. Depending on the substituents in the arylidene portion of the molecule, the charge is localized primarily on one or the other of these fragments. The mechanism of the formation of the [ArCH₂]⁺ ions observed in the mass spectra of all of the investigated compounds was established on the basis of the mass spectrum of the 1N-deuterium-labeled compound. The specific fragmentation pathways due to the ortho effect of the nitro group are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1690–1696, December, 1976.