Synthesis of (−)-pinidinone

The diastereoselective PdCl₂/CuCl₂-catalysed intramolecular methoxyaminocarbonylation of N-benzyl protected alkenyl amine 4 was used as a key step in the total synthesis of the naturally occurring piperidine alkaloid (−)-pinidinone. Commercially available (S)-propylene oxide was employed as starting material, delivering the key substrate 4 in three steps and 68% overall yield. Subsequently, the influence of various reaction parameters on the diastereoselectivity of the key cyclisation of 4 was scrutinised. Copper(II) chloride proved to be the optimum reagent and/or co-catalyst for the successful aminocyclisation-methoxycarbonylation tandem transformation of alkenyl amine 4 into the desired methyl esters 3 and 8. The latter were subsequently transformed into the title natural product.     

Synthesis and stereochemistry of (−)-rosiridol and (−)-rosiridin

The plant-derived monoterpenoids (−)-rosiridol and (−)-rosiridin can be assembled in an enantioselective manner via DIP-Cl reduction of a ketone precursor obtained by BCl₃-mediated C-C coupling of prenyl stannane and an α,β-unsaturated C₅ aldehyde. On the basis of Mosher analyses, the absolute stereochemistry 4S was assigned to (−)-rosiridol; this was confirmed by X-ray structure analysis of pentaacetylrosiridin. Glucosylation of (4S)-4-acetoxygeraniol proceeds under Koenigs-Knorr conditions in diethyl ether. (−)-Rosiridin was synthesized for the first time.     

Synthesis of (−)-lapatin B

The synthesis of (−)-lapatin B (1) has been achieved from l-tryptophan. The key reactions involve oxidative cyclization of N,N-diacetylglyantrypine (8) using PhI(OH)(OTs), and an indole-to-oxindole transformation in the penultimate step.     

Study of dehydration kinetics of heteropoly molybdate and tungstate complexes of gallium(III)

The dehydration processes of heteropoly hexamolybdate and dodecatungstate complexes of gallium were investigated. The kinetics of dehydration were studied in a flow reactor, the obtained activation energy values being 50–107 kJ/mol, and the pre-exponential factor 10⁴–10¹³s^–1. The nature of the external cation does not influence the dehydration kinetics essentially. The activation energy and pre-exponential factor values increase on transition from the high-hydrated tungstates to the low-hydrated molybdates.

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Zusammenfassung Es wurde der Dehydratierungsproze\ der Heteropolyhexamolybdat- und Dodecawolframat-Komplexe von Gallium untersucht. Die Kinetik der Dehydratierung wurde in einem Durchflu\reaktor untersucht, die erhaltenen Werte für die Aktivierungsenergie und den prÄexponentiellen Faktor betragen 50–107 kJ/mol bzw. 10⁴–10¹³s^–1. Die Kinetik der Dehydratierung wird durch externe Kationen nicht wesentlich beeinflu\t. Aktivierungsenergie und prÄexponentieller Faktor steigen beim übergang vom hochhydratierten Wolframat zum niederhydratierten Molybdat.

     

Synthesis of (+)- and (−)-isocarvone

The first synthesis of 5-isopropenyl-3-methyl-cyclohex-2-enone, (isocarvone) (2), in enantiomerically pure form is reported. Both enantiomers of 2 can be produced by manipulation of carboxylic acid 5, which is available from R-(−)-carvone (1). These materials provide new chiral building blocks that could be used in total synthesis of natural products and related optically active compounds.     

Synthesis and absolute configuration of (−)-serantrypinone

A synthesis of (−)-serantrypinone (3) has been achieved from l-tryptophan. A key reaction involves the transformation of a selenoxide to an acetate via trapping of a presumed intermediate in a seleno-Pummerer reaction.     

Synthesis of natural (−)-hamigeran B

Alkylation of lactam 10, first with iodide 15 and then with MeI, gave mainly (18:1) lactam 18. This was converted by treatment with t-BuLi and then with aqueous base into enone 4, which was elaborated into (−)-hamigeran B. A key feature of the last part of the synthesis is the use of t-BuMe₂Si-groups (as in intermediate 24) both to direct hydrogenation from the appropriate face and to protect the benzylic CO bond from hydrogenolysis.     

Synthesis and absolute configuration of (−)-chettaphanin I and (−)-chettaphanin II

An efficient synthesis of chettaphanin I and II has been achieved from ent-halimic acid. The absolute configuration of the natural products was established by nOe experiment and by X-ray analysis of chettaphanin II.     

Studies on chromium(III) hydroxide, arsenate, antimonate, molybdate and tungstate

Five water-insoluble compounds of chromium(III) have been synthesized by mixing 0.10M solutions of chromic chloride and the appropriate sodium salts in the volume ratio of 1:2, at pH 6-7. Their ion-exchange characteristics have been compared. The tungstate has the highest chemical stability and the arsenate has the highest ion-exchange capacity. Chromium(III) molybdate columns have been used to separate Pb(2+) from numerous metal ions.     

Energy transfer in mercury-doped calcium tungstate and molybdate

The luminescence of CaWO₄Hg and CaMoO₄Hg is reported. The presence of Hg²⁺ ions in the CaWO₄ lattice influences the luminescence of pure CaWO₄ drastically due to efficient energy transfer from host lattice groups to the emitting centre consisting of a tungstate group with a neighbouring mercuric ion. The luminescence characteristics of CaMoO₄Hg do not differ strongly from those of pure CaMoO₄ due to the absence of efficient energy transfer.     

Synthesis of (−)-hygrine, (−)-norhygrine, (−)-pseudohygroline and (−)-hygroline via Nef reaction

Synthesis of tropane alkaloids (−)-hygrine, (−)-norhygrine and sedum alkaloids (−)-pseudohygroline and (−)-hygroline is described from l-proline via Henry and Nef reactions.     

Synthesis of 1-aminopyrrolizidine alkaloid (−)-absouline by stereoselective aminoconjugate addition

The diastereoselective aminoconjugate addition of benzylamine and lithiobenzylamine to both E and Z-configured vinylogous proline derivatives has been investigated. The results from this study have enabled the stereoselective synthesis of the 1-aminopyrrolizidine alkaloid (−)-absouline.     

Synthesis of the marine furanoditerpene (−)-marginatone

A synthesis of the marine labdane furanoditerpene (−)-marginatone 1 has been accomplished by a short sequence of reactions starting from (+)-coronarin E 5. The key step is the stereocontrolled-intramolecular electrophilic cyclisation of the (+)-dihydrocoronarin E 6, to the tetracyclic marginatane skeleton 7, which is subsequently functionalized by allylic oxidation to give 1. As (+)-coronarin E 5 was previously synthesized from (−)-sclareol 10, the herein reported preparation constitutes the first formal total synthesis of (−)-marginatone 1, by which its absolute configuration has been confirmed.     

Synthesis of new chiral ionic liquids based on (−)-menthol and (−)-borneol

New chiral ionic liquids (CILs) based on (−)-menthol and (−)-borneol were designed and synthesized in very good yields using a simple and efficient 3-step strategy. The properties and characterization of these compounds are discussed.     

Synthesis of ent-ambrox® from (−)-nidorellol

Using ozonolysis of the acid-catalyzed cyclized products of (−)-nidorellol and air-autoxidation as the key steps, (+)-ambrox was obtained in 53% overall yield. In the course of our synthesis, we discovered that (−)-nidorellol provided (+)-ambrox instead of the expected product, (−)-ambrox. Thus the absolute configuration of (−)-nidorellol was proved to be trans-(5R^∗,7R^∗,8R^∗,9S^∗,10R^∗)-labda-12,14-diene-7α,8β-diol, which is opposite to that illustrated in a previous report.     

Synthesis of (−)- and (+)-8-fluoro-galanthamine

The synthesis of racemic 8-fluorogalanthamine and its separation into (−)- and (+)-8-fluorogalanthamine (= (4aS,6R,8aS)- and (4aR,6S,8aR)-1-fluoro-4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro[3a,3,2-ef][2]benzazepin-6-ol) is described.     

Synthesis and ion-exchange properties of cerium(IV) molybdate

Cerium(IV) molybdate, prepared under the optimum conditions of concentration, acidity etc., shows exchange capacity of 0.96 meq per g of exchanger. The sorption of a large number of metal ions has been investigated and the compound shows promising behaviour as cation exchanger. Numerous separations of analytical and radiochemical interest have been performed on the columns of this exchanger with great efficiency.     

Comparative study of iron(III) phosphate,arsenate, antimonate,selenite, molybdate and tungstate

Six water-insoluble compounds of iron(III) have been synthesized by mixing solutions of ferric nitrate and the acidic oxides of elements of Groups V and VI. These compounds have been characterized on the basis of chemical-analysis, pH titration, thermogravimetry, solid-reflectance, IR and Mössbauer studies. Their chemical, thermal and ion-exchange characteristics have been compared.     

Rubidium gadolinium bis­(tungstate)

The structure of rubidium gadolinium bis­(tungstate), RbGd(WO₄)₂, has been determined. The crystal is built up from corner‐ and edge‐sharing WO₆ octa­hedral and GdO₈ polyhedral groups, giving rise to a Gd–WO₄ polyhedral backbone surrounding structural cavities filled with Rb⁺ cations. The Gd and Rb atoms lie on twofold axes.     

Synthesis of enantiopure concave (+)-avenaciolide and (−)-canadensolide skeletons

Simultaneous regio- and chemoselective reduction of the carboxyl group of (2S,3S)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid (garcinia acid), isolated from plant sources in large amounts, has been carried out to reach the core concave bislactone structures of fungal metabolites (+)-avenaciolide and (−)-canadensolide in one and two steps, respectively.