Absolute Konfiguration der Equisetumalkaloide (+)-Palustrin,Palustridin ((+)-Monohydrochlorid) sowie der (−)-Dihydropalustraminsäure und weiterer Derivate. 16. Mitteilung über Schachtelhalmalkaloide

Determination of the absolute configuration of alkaloids from Equisetum sp.,e.g. (+)-palustrin, palustridin ((+)-hydrochloride), and (?)-dihydropalustramic acid and derivatives The absolute configuration of the title alkaloids has been determined using chiroptical methods (ORD., superposition of CD. values of appropriate models and a modified Horeau method). (+)-Palustrin is (13R, 17 S, 1′S)-17-(1-hydroxypropyl)-1,5,10-triazabicyclo [11.4.0]heptadec-15-en-11-on.     

Über die Synthese der Pilocarpus-Alkaloide Isopilosin und Pilocarpin,sowie die absolute Konfiguration des (+)-Isopilosins

A novel synthesis for rac-pilosinine ( 6 rac) and transformation of (+)-pilosinine ( 6 ) into the pilocarpus alkaloids (+)-isopilosine ( 9 ) and (+)-pilocarpine ( 18 ) are described. By correlation via 5 with 18 the absolute configuration of (+)-isopilosine ( 9 ) is established.     

Über die Struktur der makrocyclischen Spermidin-Alkaloide Oncinotin,Neooncinotin und Isooncinotin. 151. Mitteilung über Alkaloide

Three spermidine alkaloids – oncinotine ( 1 ), neooncinotine ( 3 ), and isooncinotine ( 2 ) – have been isolated from the stem bark of Oncinotis nitida BENTH . (Scheme 1); 1 and 3 are so far an unseparable mixture. However, by treatment of this mixture with K-t-butoxide, neooncinotine is completely converted into isooncinotine, and oncinotine, the main alkaloid, is obtained in pure form. The structural assigment of these alkaloids is based on chemical and spectral evidence. Thus oncinotine ( 1 ) has been degraded via 24 (Scheme 4) and 32 to the putrescine derivative 35 and the piperidine derivative 34 (Scheme 5). Similarly neooncinotine ( 3 ) and isooncinotine ( 2 ), have given 34 along with the 1, 3-diaminopropane derivative 36 (Scheme 5). The major decomposition pathways of 24 , 35 and 36 in the mass spectra are described in Schemes 8, 6 and 7 respectively. The absolute configuration of 1 , 2 and 3 is derived by chiroptical correlations with (R)-(?)-N-methylconiine ( 38 ).     

«Alkaloide» in tierischem und menschlichem Gewebe. 6. Mitteilung [1] [2]. Synthese und absolute Konfiguration chiraler 2, 3, 10, 11 - Tetrahydroxy-8-methyl-berbine [3]

Synthesis and absolute configuration of chiral 2, 3, 10, 11-tetrahydroxy-8-methylberbines [3] . The synthesis and absolute configuration of the four optically active berbines Xa, b and XIa, b are described. These compounds consitute potential ‘alkaloids’ obtained by condensation of either R-(+) or S-(?)-norlaudanosoline (THP, III) with acetaldehyde, a major metabolite of ethanol.     

Über Juliprosin,ein weiteres Alkaloid aus Prosopis julifloraA.DC. 180. Mitteilung über organische Naturstoffe

Juliprosine, a Further Alkaloid Isolated from Prosopis juliflora A .DC . By catalytic hydrogenation of the second base juliprosine ( 2 ) isolated from Prosopis juliflora (Leguminosae) the hexahydroderivative 5 was formed. The same product was obtained also by catalytic hydrogenation of juliprosopine ( 1 ) of known structure. The absolute configuration of 2 was deduced by comparison of [M]_D values of Prosopis alkaloids of known absolute configuration.     

Konstitution und absolute Konfiguration der Rhoeadin-Alkaloide (+)-Alpinigenin und (+)-cis-Alpinigenin

The constitution and absolute configuration of the rhoeadine alkaloids (+)-alpinigenine and (+)-cis-alpinigenine. The fundamental structure of the hemi-acetal phenylbenzazepine alkaloid (+)-alpinigenine ( 1 ), isolated from Papaver bracteatum LINDL ., was derived essentially from ¹H-NMR.- and mass-spectra of 1 and its derivatives 7, 10 and 14 (cf. Scheme 2). The positioning of the four methoxy groups in the two aromatic rings could be deduced from the ¹H-NMR.-spectra of the N-oxides 14 and 15 in which, as a result of favourable sterical and conformational behaviour, an interaction exists between the N-oxide oxygen atom and one of the two ortho protons in ring C. The B/D-trans-fused 1 undergoes isomerization in 1N HCl to cis-alpinigenine ( 16 ). A stereochemical correlation between bases in the trans-and cis-series was enabled via an Emde degradation of the corresponding methylacetal-methyliodides 21 resp. 19 leading to the enantiomeric isochroman derivatives 22 resp. 23 which are achiral at C (2) (Scheme 4). The configuration at C (14) in the hemi-acetals (eg. 1 and 16 ) and the methyl ethers (eg. 7 and 8 ) is discussed in detail (cf. Scheme 7). (+)-Alpinigenine ( 1 ) has the (1S, 2R, 14R) configuration and (+)-cis-alpinigenine ( 16 ), in chloroform or acetone solution, the (1R, 2R, 14R) configuration.     

Indolalkaloide aus den Blättern von Hedranthera barteri (Hook. f.) Pichon. 146. Mitteilung über Alkaloide

From the leaves of the West African plant (Apocynaceae Hedranthera barteri) has been isolated the phenolic (?)-desmethyl-vobtusine ( 3 ), alongside the already known bisindole alkaloids (?)-goziline ( 1 ) and (?)-vobtusine ( 2 ). The new alkaloid 3 has been spectroscopically characterised and correlated with (?)-vobtusine ( 2 ). Furthermore, the ‘monomeric’ alkaloids (?)-hedrantherine ( 4 ) and (?)-17-hydroxy-hedran-therine ( 5 ) were found in the leaves of H. barteri. Both of these alkaloids contain a cyclic semiacetal group. These bases and their derivatives possessing an unchanged β-anilinoacrylester group show, in the mass spectrometer, the same characteristic fragmentation as vincadifformine ( 11 ), whilst their 2,3-dihydroderivatives bear more of a resemblance to aspidospermine. From the strongly negative Cotton effect of 4 and 22 at 300–350 nm follows the absolute configuration in these bases of centre 12. Hedrantherine ( 4 ) represents the lower half of the bisindole type of vobtusine bases. The upper half has previously been encountered in form of the alkaloid beninine in the rootbark of H. barteri.     

The Absolute Configuration of 3-Methylpyrrolidine Alkaloids from Poison Glands of Ants Leptothoracini (Myrmicinae)

The absolute configuration of 3-methylpyrrolidine alkaloids isolated from the poison gland of ants Leptothoracini was determined as (3R). The enantiomeric separation by chiral gas chromatography and unambiguous structural assignment of the target compounds are described.     

Peduncularistin,Triabunnin und Aristolarin,drei neue Indolalkaloide aus Aristotelia peduncularis (LABILL.) HOOK. F., 191. Mitteilung über organische Naturstoffe

Peduncularistine, Triabunnine and Aristolarine, Three Ne Indole Alkaloids from Aristotelia peduncularis (L_LABILL.) H_OOK, F. Peduncularistine ( 1 ), triabunnine ( 2 ) and aristolarine ( 3 ), three new indole alkaloids, have been isolated from Aristotelia peduncularis (L_ABILL.) H_OOK. F.; the structure and absolute configuration of 1 were elucidated on the basis of spectroscopic data and confirmed byt transformation of 1 into aristeserratine ( 4 ), a known alkaloid isolated from the same plant. The proposed structure 2 for the second alkaloid and its absolute configuration were established but spectroscopic means and by partial synthesis from 4 . The relative configuration of 3 was postulated on the basis of spectroscopic and biogenetic arguments.     

Synthesis of (+)-(S)-Streptenol A and Biomimetic Synthesis of (2R,4S)- and (2S,4S)-2-(Pent-3-enyl)piperidin-4-ol

(+)-(S)-Streptenol A is synthesized by coupling a 1,3-dithiane with an optically pure epoxide. The absolute configuration of (+)-(S)-streptenol A is thereby correlated with that of (S)-malic acid. Stereoselective reduction of an oxime that could easily be prepared from streptenol A gave the (3S,5R)- and (3S,5S)-aminostreptenols, and after cyclization, configurationally pure 2,4-functionalized piperidine alkaloids.     

Stereocontrolled Organocatalytic Strategy for the Synthesis of Optically Active 2,3‐Disubstituted cis‐2,3‐Dihydrobenzofurans

An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented.     

Syntheses of the cylindrospermopsin alkaloids

An intramolecular 1,3-dipolar cycloaddition has efficiently constructed the A-ring portions of the cylindrospermopsin alkaloids. A nitro-aldol addition of an elaborated nitroalkane to a pyrimidine aldehyde followed by an intramolecular reductive guanidinylation has enabled the syntheses of all three alkaloids in this family in 18-19 steps. We report the first asymmetric synthesis of cylindrospermopsin, unambiguously assigning its absolute configuration.     

Stoffwechselprodukte von Mikroorganismen. 50. Mitteilung. Die Konfiguration der Arcanose

The L -xylo configuration of arcanose, a sugar from the antibiotic lankamycin, has been proven by its transformation into cladinose. The determination of the absolute configuration at C-3 of arcanose and cladinose has been accomplished utilizing a new procedure.     

New Cembrane-Type Diterpenoids from the South China Sea Soft Coral Sinularia nanolobata

In the present study,nine new cembrane-type diterpenoids,namely ximaonanolobatins A—I(1—9),together with six related known analogs(10—15)and four known tetraprenylated alkaloids malonganenones D,E,H,and K(16—19)were isolated from the soft coral Sinularia nanolobata collected off the Ximao Island in the South China Sea.The structures of 1—9 were robustly established by a combination of detailed spectroscopic analyses,chemical reactions,quantum mechanical(QM)-NMR methods,biogenetic consideration,and the comparison with those literature data.The absolute configuration of 1 was confirmed by X-ray diffraction analysis,and the absolute configuration of 2 was determined by QM-NMR calculations and chemical transformation.In addition,the absolute configuration of 3 was determined using the modified Mosher's method.All these isolates were evaluated for their anti-inflammatory and anti-tumor activities.The results showed that only compound 15 exhibited potential anti-inflammatory effect against LPS-induced TNF-αrelease in RAW264.7 macrophages with an IC50 value of 12.6μmol/L.     

Alkaloids ofLiriodendron tulipifera

The alkaloids of the tulip treeLiriodendron tulipifera L., family Magnoliaceae, are considered. More then 20 alkaloids have been isolated during different vegetation periods from various organs of the plant growing in Uzbekistan, and these have been assigned to the aporphine alkaloids and their dehydro, oxo, and 7-hydroxy derivatives; only two alkaloids proved to be derivatives of proaphorphine and of tetrahydroberberine. On the basis of the results of a comparative study of the NMR spectra of aporphines unsubstituted in ring D and some chemical transformations, the structure and configuration of the (R)-3-hydroxy-1,2-dimethoxyaporphine have been proposed for the new alkaloid lirinine. The absolute configurations, possible biogenetic interconnections, and mutual transitions of the alkaloids ofL. tylipifera that are derivatives of aporphine, oxoaporphine, and dehydroaporphine are discussed. A summery table is given which includes 41 alkaloids found in this plant.Institute of the Chemistry of Plant Substances of the Uzbek SSR, Academy of Sciences, Tashkent. Tashkent Agricultural Institute. Translated from Khimiya Prirodnykh Soedenii, No. 5, pp. 628–638, September–October, 1987.     

Divergent Asymmetric Total Synthesis of (−)-Voacafricines A and B

A divergent asymmetric total synthesis of voacafricines A and B, hexacyclic monoterpene indole alkaloids, has been accomplished featuring the following key steps: a) a catalyst-controlled asymmetric Pictet–Spengler reaction of 6-methoxytryptamine with a chiral α-ketoester affording a 1,1-disubstituted tetrahydro-β-carboline in excellent yield and diastereoselectivity; b) oxidative cleavage of a 3,5-disubstituted cyclopentene furnishing a dialdehyde intermediate, which was effectively differentiated through spontaneous cyclization with the neighboring hydroxy and secondary amine functions; c) intramolecular nucleophilic addition of a tertiary amino nitrogen atom to the in situ generated oxonium species generating stereoselectively an unprecedented 8-alkyl octahydro-2H-5,8-methanofuro[2,3-b]azepin-8-ium motif bearing five contiguous stereocenters. The synthesis confirmed the absolute configuration of these two natural products.     

Isoquinoline alkaloids from Asimina triloba

A new aporphine glycoside, (-)-anolobine-9-O-β-D-glucopyranoside was isolated from the twigs of pawpaw (Asimina triloba) along with 7 known alkaloids including five aporphine alkaloids (anolobine, nornuciferine, norushinsunine, liriodenine, and lysicamine), a proaporhine alkaloid (stepharine), and a tetrahydrobenzylisoquinoline alkaloid (coclaurine). Among these compounds, nornuciferine, lysicamine, stepharine, and coclaurine are reported for the first time from this plant. The structure of the new compound was elucidated by spectroscopic methods, including 1?D, 2?D NMR, and HRESI-MS. The absolute configuration of compounds 1, 2, 7 and 8 was determined by CD experiment.     

Lycodine‐Type Alkaloids from Lycopodium casuarinoides

Two new lycodine‐type alkaloids, huperzinine N‐oxide ( 1 ) and 8,15‐dihydrohuperzinine ( 2 ) as well as five known compounds, huperzinine ( 3 ), huperzine B ( 4 ), huperzine D ( 5 ), N‐demethylhuperzinine ( 6 ), and β‐obscurine ( 7 ), were isolated from the club moss Lycopodium casuarinoides. The structures of 1 and 2 were elucidated by spectroscopic methods and chemical transformation. The absolute configuration of 1 was established by chemical correlation with 3 , and that of 2 was determined by its CD spectrum.     

Synthese der enantiomeren 2-Pyrrolidinessigsäuren

Synthesis of the enantiomeric 2-pyrrolidineacetic acids. Starting from the enantiomeric Z-prolines ( 1 ) the title compounds 9 were prepared in optically pure form by using the Arndt-Eistert process. It could be shown by chemical correlation that the stereochemical determining step of the reaction sequence, the Wolff rearrangement of the N-acylated diazomethyl ketones 5 , proceeds with strict retention of configuration. Some known chiroptical methods for determination of absolute configuration were applied to the target compounds.     

Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher Herkunft

The Absolute Configuration of Iridals and Cycloiridals of Different Origin Natural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C₃₁-triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco-ring-A iridal has the same stereo-chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.