Bibliothek

Notizen: Structure of the Sesquiterpenes of Petasites hybridus (L.) G. M. et SCH.: Petasol and Isopetasol DerivativesThe structure of 11 compounds of the sesquiterpene fraction of petasites hybridus has been determined by combination of spectroscopic methods, especially by analysis of the 360-MHz-1H-NMR. spectra. Most natural products are esters of two isomeric sesquiterpene alcohols, characterized by an eremophilan skeleton, namely of petasol as well as of isopetasol. The structure of one key product has been confirmed by X-ray analysis.

Notizen: Reactions of 3-Dimethylamino-2,2-dimethyl-2H-azirine with NH-Acidic Heterocycles; Synthesis of 4H-ImidazolesIn this paper, reactions of 3-dimethylamino-2,2-dimethyl-2H-azirine (1) with heterocyclic compounds containing the structure unit CO—NH—CO—NH are described. 5,5-Diethylbarbituric acid (5) reacts with 1 in refluxing 2-propanol to give the 4H-imidazole derivative 6 (Scheme 2) in 80% yield. The structure of 6 has been established by X-ray crystallography. Under similar conditions 1 and isopropyl uracil-6-carboxylate (7) yield the 4H-imidazole 8 (Scheme 3), the structure of which is deduced from spectral data and the degradation reactions shown in Scheme 3. Hydrolysis of 8 with 3N HCl at room temperature leads to the α-ketoester derivative 9, which in refluxing methanol gives dimethyl oxalate and 5-dimethyl-amino-2,4,4-trimethyl-4H-imidazole (10). On hydrolysis the latter is converted to the known 2,4,4-trimethyl-2-imidazolin-5-one (11) [6]. Quinazolin-2,4 (1H, 3H)-dione (12) and imidazolidinetrione (parabanic acid, 14) undergo with 1 a similar reaction to give the 4H-imidazoles 13 and 15, respectively (Schemes 4 and 5).In Scheme 6 two possible mechanisms for the formation of 4H-imidazoles from 1 and heterocycles of type 16 are formulated. The zwitterionic intermediate f corresponds to b in Scheme 1. Instead of dehydration as in the case of the reaction of 1 with phthalohydrazide [3], or ring expansion as with saccharin and cyclic imides [1] [2], f, undergoes ring opening (way A or B). Decarboxylation then leads to the 4H-imidazoles 17.

Notizen: Triterpenoids from ‘Oakmoss’ (Evernia Prunastri (L.) ACH.)Seven triterpenoids have been isolated from ‘oakmoss’ (Evernia Prunastri (L.) ACH.) extracts by column chromatography and identified as friedelin (1), taraxerol (2), 29-nor-21 α-hopan-3,22-dione (3), moretenone (4), ursolic acid (5), lupeol (6) and lanosterol (7).

Notizen: Nucleotides. IX. Synthesis and properties of 1-(2′-deoxy-D-ribofuranosyl)-lumazin-3′-monophosphatesThe synthesis of various 1-(2′-deoxy-α-[and β-]D-ribofuranosyl)-lumazine-3′-monophosphates 25--30 starting from the corresponding pteridine nucleosides 1--6 is described. Monomethoxytritylation in 5′-position to 7--12, phosphorylation by cyanoethylphosphate to 13--18, and deprotection by acid and base treatment afforded the lumazine nucleotides 25--30 in good overall yield. The various reaction products have been characterized by physical means, such as UV. spectra, pK-values and their chromatographical and electrophoretical behaviour. Enzymatic dephosphorylations by alkaline phosphatase led to the starting material 1--6 with a 3--4 times slower hydrolysis rate in comparison to Tp.

Notizen: Intramolecular Substitution under Inversion at the Threemembered Ring of 7exo-Bromobicyclo[4.1.0]heptan-3endo-ol yielding a Tetrahydrofuran RingThe reaction 1a → 2a involving substitution at a cyclopropane carbon atom can be observed only with the bromophilic alkyllithium reagents but not with the bases lithium diisopropyl amide (LDA) (Table 1) or potassium t-butoxide (KTB). The mechanism must be an insertion as outlined in Scheme 1. - The monobromides 1b, 1c and 1d are prepared stereoselectively from the acetal 3a. Again, cyclization of 1b takes only place with LDA in the presence of alkyllithium (Table 2, entries 1--4) suggesting an insertion mechanism (route (a) or (b) in Scheme 2). In contrast, KTB effects the substitution in high yield with no loss (from 1c) or incorporation of deuterium at the cyclopropane substitution center (Table 2, entries 5--7); the possibility is discussed that this process is an SN2-type reaction.

Notizen: Nucleotides. X. Synthesis and properties of dinucleoside monophosphates with 2′-deoxyadenosine and 1-(2′-deoxy-β-D-ribofuranosyl)-lumazines as building blocksThe synthesis of various dinucleoside monophosphates 16--20 consisting of 2′-deoxyadenosine and 1-(2′-deoxy-β-D-ribofuranosyl)-lumazines via the triester approach is described. The fully protected phosphotriesters 6--10 as well as the partially deblocked intermediates 11--15 have also been isolated and characterized by physical means. Intramolecular interactions in 16--20 have been investigated by the determination of the hypochromicities and CD. spectra revealing a more or less distinct stacking effect in dependence of the 6,7-substituents in the lumazine moiety as well as the polarity of the internucleotidic linkage. Enzymatic degradations of the dinucleoside monophosphates with snake venom and spleen phosphodiesterase are depending strongly on various structural features indicating a much lower substrate specificity especially in presence of 6,7-diphenyl-lumazine as an aglycone with the latter enzyme.

Notizen: The processes involved in photoenolisations are theoretically simulated by an ab initio SCF-CI method, using cis-2-butenal as a prototype structure. The prominent role of the hydroxyl group conformation in the resulting transient (2a) is emphasized; its rotation ‘out of the reaction site’ allows the next reaction paths to proceed exothermally. The equilibration of the different types of twisted biradicals in the triplet manifold, which only involves a low energy barrier, is thus possible, populating in quite equal weights the precursors of both E- and Z-dienols. In the singlet state, the formation of the Z-isomer is expected to be kinetically dominant. An examination of the role of the substituents suggests that, in related systems, the steric crowding induces important structural relaxation of the dienol geometries.

Notizen: The water exchange on [Mn(H2O)6](ClO4)2 in aqueous solution has been studied as a function of pressure (up to 250 MPa), measuring 17O-FT-NMR. linewidths of the free water resonance at 8.13 MHz. A pressure independent volume of activation, ΔV≠ = -6.2 ± 0.2 cm3 mol-1 is obtained, producing a clear evidence that, contrary to general belief, the mechanism for solvent exchange on Mn2+ is an associative interchange (Ia).

Notizen: The radical anions of the following substituted [2.2]paracyclophanes have been characterized by ESR. and ENDOR. spectroscopy: 4, 16-dicyano- (o-2), 4, 12-dicyano- (p-2), 4,5,12,13-tetracyano- (3) and 4,5,12,13-tetrakis (alkoxycarbonyl)- [2.2]paracyclophanes (4-R, where R = Me, Et, iPr or tBu is the ester alkyl group); 4,5-bis(methoxycarbonyl)[2.2]paracyclophane-12, 13-dicarboxylic anhydride (5); [2.2]paracyclophane-4,5:12, 13-tetracarboxylic bisanhydride (6) and bisimides (7-R, where R = H, D, Me or Ph is the substituent at the imide N-atom). Comparison of the hyperfine data for these radical anions with those for analogously substituted derivatives of benzene indicates that the most prominent coupling constants are approximately halved on passing from the latter to the former. Lowering of the symmetry, as a consequence of ion pairing, has been observed for the radical anions 4-iPr\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4-tBu\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} associated with the counterion K⊕ in 1,2-dimethoxyethane at 183 K, but not for 4-Me\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4-Et\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} under the same conditions. This result suggests that the migration of K⊕ between the preferred sited in two equivalent ion pairs is slowed down by the steric hindrance arising from the bulky iPr and tBu ester groups.

Notizen: The Cope Rearrangement, a Reaction for Repeatable Ring ExpansionsStarting with the unsaturated β-ketoesters of type I, a vinyl group is introduced into the β-position by 1,4-addition of vinyl magnesium chloride to give II (Scheme 3). Treatment of the β-ketoester II with phenyl vinyl sulfoxide in the presence of sodium hydride yields the sulfoxides III, which on thermolysis lead to the α, β-divinyl ketoesters of type IV via elimination of sulfinic acid (Scheme 3). The Cope-System IV undergoes rearrangement to V, which is again an unsaturated β-ketoester. The latter is suitable for a further ring expansion sequence. These reaction steps were carried out with the nine-, twelve- and fifteen-membered ketoesters 32, 33 and 34, as well as with the open-chain compound 35 (Table 1). With the cyclohexane derivative 31, ring expansion could not be achieved with the described sequence.

Notizen: p-Toluenesulfonylhydrazones of α, β-unsaturated ketones undergo an alkynone fragmentation in high yield when treated with electrophiles under basic conditions. With N-bromosuccinimide in alcohols, the p-tosylhydrazones 4a and 4b yielded in a one-pot reaction the cyclic 4-alkyn-1-ones 5a and 5b; these were converted to Exaltone® (1a) and muscone (1b) on catalytic hydrogenation.

Notizen: The 31P{1H} nuclear Overhauser effects (NOE's) and 31P-spin-lattice relaxation times (T1) for a series of trans-[PdCl2P2], P = PEt3, PPr3n, PBu3n, PMe2Ph, PMePh2, P(p-Tol)3, P(cyclohexyl)3 complexes are reported. Both the NOE and T1 values depend upon the choice of solvent. The dipole-dipole mechanism dominates the spin-lattice relaxation of the coordinated phosphorus atom with the T1 values for the PEt3, PPr3n, and P (cyclohexyl)3 complexes decreasing with increasing molecular weight of the phosphine.

Notizen: Dye-sensitized photooxygenation (1O2-reaction) of the symmetrically 3,3-dialkyl-substituted allyl alcohols 1-6 (A, Table 1) and the E- and Z-isomers of the 3-methyl-3-alkylsubstituted allyl alcohols 7-11 (A1, Table 2) has been studied. The α, β-epoxyaldehydes B and B1 and the β-hydroperoxy-homoallyl alcohols C, C1 and D1 were practically the sole oxygenation products formed. The rate and selectivity of the 1O2 additions were found to be markedly dependent on the degree of substitution (i.e. H-availability) at the allyl position which is Z-orientated to the carbinol group. The allyl alcohols with a Z-3-methyl group, 1 and the E-isomers of 7 to 10, showed practically the same reactivity towards 1O2 and formed only the two oxygenation products of type B1 and C1 (ratio close to 60:40). In contrast, the allyl alcohols with a Z-3-methylene group, 2 and the Z-isomers of 7 to 9, reacted more slowly with 1O2 and yielded all the three possible products B1, C1 and D1 in a very different ratio of ∼ 80:10:10. However, from both the E- and Z-isomers of the alcohols 7 to 10 the formations of the two oxygenation products were always strongly favoured (85-100%) which result from 1O2 additions at the disubstituted side of the double bond. This behaviour is thus completely analogous to that of the corresponding trisubstituted olefins previously studied [1]The same side-specific selectivity in 1O2 ene additions to several E/Z-isomeric and deuterium-labelled olefins has also been described recently by C.M. Stephenson et al. [2] (we thank Dr. V. Rautenstrauch and Prof. C.W. Jefford for informing us about this work). The similar behaviour of enol ethers, which react with 1O2 preferentially at the RO-substituted side, had been observed earlier by C.S. Foote et al. [3] and extended to numerous derivatives by J.M. Conia et al. [4] [5]. and follows a new selection rule, termed syn-preference [1], in the ene addition of 1O2.

Notizen: The Li/K-derivative 6 is used to synthesize the title compounds (3a and 4a) in enantiomerically pure form from (-)-(S)-propylene epoxide. The C,C bond forming key step leading to the hydroxyketone 7 is followed by cyclization (→, 8), Beckmann cleavage (→ 9b) and hydrolysis to 3a (recently isolated from civet). Base treatment of 3a opens the ring (10) to give the hydroxyacid 1 which is cyclized to the macrolide 4a. The synthetic usefulness of the highly nucleophilic doubly reduced dienone system 6 as d5-reagent (see synthons 2) is thus demonstirated.

Notizen: Stereoselective synthesis of cyclopropylsugarsUse of the phase-transfer catalysis significantly increased the yield of the reactions leading to the known compounds 2 and 3. Stereoselective cyclopropylation of 3 and 4 and 8, was brought about using in the first instance the Simmons-Smith's reagent, whereas the reaction of dichlorocarbene led to 6 easily dechlorinated to 8. Both diastereoisomeric cyclopropylsugars 4 and 8 were transformed into the corresponding ethyl glycosides.

Notizen: In contrast to the behavior of 4-substituted-1,2, 4-triazoline-3, 5-diones which add to the syn-face of the cyclohexadiene with respect to the hetero-ring in propellanes of type 1, dienophiles containing a C, C double bond instead of an N, N double bond add exclusively to the anti-face of the same substrates. This supports our thesis that these reactions are controlled by secondary orbital interaction between the N, N dienophiles and the hetero-ring of the substrates, an interaction which cannot exist in the C, C dienophiles.

Notizen: In addition to the two new sterols verongulasterol 11 and 25-dehydroaplysterol 13 of Verongia cauliformis3), which were reported earlier [2] [3], the minor and trace sterols of this sponge include five new sterols listed in the title (with the exception of the known 24 S-methyl-cholesta-5, 25-dien-3β-ol (codisterol, 1b). The isolation of the 24(R)-epimer of codisterol is of interest, as this compound is a possibly biosynthetic precursor for aplysterol 12, 25-dehydroaplysterol 13, and verongulasterol 11 (all 24R) which occur in the same sponge [2]. A partial synthesis from fucosterol (4) of 24 (R + S)-isopropenylcholesterol (9), and of 24-isopropylcholesterol (10) is described.

Notizen: On the biogenesis of betacyanins. Expaiments with [2-14C]-dopaxanthineLabelled dopaxanthine is prepared from betanin by a double exchange procedure replacing first its cyclodopa part by diethylamine and effecting the second exchange with 2-[14C]-dopa on the purified intermediate ‘DEA-betalain’; the specific activity delivered with the dopa allowed accurate determination of ∊ in the electronic spectrum of dopaxanthine (λmax 488 nm, ∊ = 41.800). The C(2)-labelled dopaxanthine is incubated into the fruits of Opuntia bergeriana. The incorporation rates into betanin are found to correspond approximately to those obtained in earlier experiments with labelled dopa alone: Only 1--5% of the label showed up in the cyclodopa moiety of the betanin (which is isolated as cyclodopa-glucoside) whereas 99--95% of the radioactivity was associated with the betalamic acid part (recovered in form of indicaxanthine).

Notizen: E.S.R. study of radiation damage in a single crystal of sodium dimethyl arsonateL'irradiation aux rayons X, à 77 K, d'un monocristal de diméthylarsinate de sodium provoque le piégeage de \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} \left({\rm O} \right){\rm As}\left({{\rm O}^ -} \right)\mathop {\rm C}\limits^ \cdot {\rm H}_{\rm 2} $\end{document} et de (CH3)2AsO2--. En fonction de la température ces radicaux se réorientent ou donnent naissance à de nouvelles espèces radicalaires. Les tenseurs g et de couplage hyperfin avec 75As ont été déterminés à 105 K, 165 K, 215 K et 295 K et permettent de proposer une identification de plusieurs espèces radicalaires localisées sur l'atome d'arsenic. Le rǒle de la température d'irradiation et l'influence de l'oxygène sur la réactivité des radicaux piégés dans le cristal sont également étudiés.

Notizen: Friedel-Crafts reactions of aromatic derivatives with 1,4-dicarbonyls 2,3-éthylenic compounds. Part IV. Reactions of 5-hydroxy or 5-chloro 3,5-dimethyl or 4,5-dimethyl 2 (5 H) furanonesWe studied the Friedel-Crafts reactions of 2-(5H)-furanones. In the presence of sulfuric acid and of an aromatic derivative, 5-hydroxy- or 5-chloro-5-methyl-2-(5H)-furanones with one methyl group either in the 3 position, or in the 4 position generally give the corresponding 5-aryl-2-(5H)-furanones, while with aluminium chloride, it is possible to obtain, when a reaction takes place, isomeric 1H-indenecarboxylic acids. However, in a particular case, an addition to the substrate's double bond is observed. The 3-aryl-5-hydroxy-tetrahydrofuran-2-one obtained is methylated in two ways and gives either a cyclic product, or a linear one. In two cases tautomerism between 1H-1-indenecarboxylic acid and 1H-3-indenecarboxylic has been shown by 1H-NMR.

Notizen: Derivatives of enose- and ynosephosphonates and related compounds. Preliminary communicationThe gem-dibromo terminal enoses 1 and 7 are convenient sources of glycosylacetylenes which upon reaction with phosphorus electrophiles gave the phosphorusbearing acetylenic sugars 4, 5 and 8. Compounds 5 and 8 underwent cycloaddition reactions leading to isoxazolyl-C-glycosides 6 and 9 respectively. The nitroolefinic sugar derivative 11 gave upon bromination-dehydrobromination the first example of a new kind of potentially useful synthetic intermediates, the gem-bromonitroenose 12. The enosephosphonate 13 was also prepared from 11. The diglycosylhydroxylamine 18 represents another type of phosphorus-bearing acetylenic sugar derivative. Some 1H- and 13C-NMR. data relative to the new types of phosphorus-containing sugar derivatives synthesized are given.

Notizen: Note on a preparation of β, γ-unsaturated carboxylic acid derivatives using the amide acetal Claisen rearrangement3-(Trimethylsilyl)allyl alcohols smoothly undergo the amide acetal Claisen rearrangement furnishing allyl silanes. Subsequent protolysis with HF at -20° provides a convenient, stereoselective method for the preparation of β, γ-unsaturated carboxylic acid derivatives. Three model examples illustrate the procedure.

Notizen: Isomerization of the Bis(triphenylphosphine)platin(0) Complexes of Bicyclo[4.2.1]non-1-ene and Bicyclo[4.2.1]non-1(8)-eneIsomrisation of the Bredt-Olefins 3 and 7 as the bis (triphenylphosphine)-Pt(0) complexes 1 and 8, respectively, has been observed. The bridgehead-olefin 3 as well as the bicyclic olefins 4, 5 and 6 have also been isomerized with catalytical amounts of (ethylene)bis(triphenylphosphine)platinum(0) (2).

Notizen: Use of the ‘Zip’ reaction for the synthesis of a 53-membered polyminolactamThe synthesis of N-(39-amino-4, 8, 12, 16, 20, 24, 28, 32, 36-nonaaza-nonatriacontyl)-12-dodecanlactam (1)In ‘5’ wurden die Verbindungen 1 als 1-(39-Amino-4,8,12,16,20,24,28,32,36-nonaazanonatriacontyl)-1-azacyclotridecan-2-on, 4 als 7-Chlor-1-phthalimido-4-tosyl-4-azaheptan, 5 als 7-Jod-1-phthalimido-4-tosyl-4-azaheptan und 20 als 1,5,9,13,17,21,25,29,33,37,41-Undecaazatripentacontan-42-on bezeichnet. has been described. The formation of synthon 2 , used for the chain extension of the known 12[6] shown in Scheme 2 , is demonstrated in Scheme 1 . In presence of base (KAPA-reagent), 1 undergoes the so called ‘Zip’-reaction resulting in a ring-expansion by 40 members which leads to 20 .

Notizen: Cyclopropyl ketones are readily cleaved under neutral conditions at room temperature by the combined action of acetyl methanesulfonate and nucleophiles such as Br-, I-, and MsO-. The high-yield reaction involves regiospecific enol acetate formation with a stereoselectivity of nucleophile addition which is compatible with an SN2-type opening of the cyclopropyl ring.

Notizen: Preparation of 6exo, 7exo-bis (methylidene)-tricyclo[3.2.1.02,4]octane (6) is described. The reactivity of 6 towards tetracyanoethylene is evaluated and compared with that of exo-2,3-epoxy-5,6-bis (methylidene)norbornane (5), 2,3-bis-(methylidene)norbornane (1) and other related dienes. The cyclopropane group in 6 exerts an unsignificant rate retardation effect on the Diels-Alder reactivity of this diene relative to that of 1, whereas a relatively important rate retardation effect is caused by the exo-oxirane ring in 5. The observed effects are probably due to electronic factors (through-space and through-bond interactions).

Notizen: Leaf-gland pigments from labiatae: structures of 13 diterpenoids (coleons) from Solenostemon sylvaticus (GÜRKE) T.T. AYE and Coleus garckeanus VATKEThe above mentioned East-African labiatae have been investigated for their leaf-gland pigments. The two plants contain very similar abietanoic diterpenoids. Besides the already known coleons O (5a) and W (1a), 11 novel compounds have been isolated and their structures established:Diosphenol: 16(or 17)-O-acetyl-coleon W (1b).Diketones: Coleon X (16 or 17)-acetoxy-11, 12, 14, 17 (or 16)-tetrahydroxy-abieta-8, 11, 13-triene-6,7-dione (2a); 16 (or 17)-O-acetyl-coleon X (2b).Spiro-coleons: 6-O-acetyl-19-acetyloxy-coleon Q (3b); 12-O-desacetyl-7-O-acetyl-19-acetyloxy-coleon Q (3c); 12-O-desacetyl-7-O-acetyl-19-acetyloxy-coleon P (3e); 12-O-desacetyl-7-O-acetyl-3β, 19-diacetyloxy-coleon Q (4b); 19-acetyloxy-coleon O (5b); 12-O-desacetyl-6-O-acetyl-17-acetyloxy-coleon P (7); 7-desoxy-12-O-desacetyl-3-acetyloxy-coleon N (6b); coleon Z (8).Compound 7 contains a spiro cycloprope unit, substituted by one carbonyl and two carbinol functions. Compound 8 (Coleon Z) contains a unique cis-butadiene unit formed from C(3)-C(4)-C(18)-C(19).

Notizen: Carbocyclic compounds from monosaccharides. II. Transformations in the mannose seriesUpon treatment with Zn in refluxing aqeous ethanol or butanol, the anomeric mannopyranosides 11 and 14 yielded the aldehyde 15 which was subjected (via its N-methyl-nitrone) to an intramolecular nitrone-olefine cycloaddition leading diastereoselectively to 18 in a yield of 64% from 14. Minor products of this reaction sequence were the compounds 19, 20 and 21. Similarily, the easily accessible unsaturated furanose 26, upon treatment with N-methyl-hydroxylamine gave the isoxazolidines 27 (84%) and 28 (3%), thus showing that a free 4-hydroxy group is not detrimental to this intramolecular nitrone-olefin cycloaddition. The configuration of 18, 27 and 28 (resp. 29) were determined by spectroscopic means; that of 27 was further proven by transformation into the compound 31, of which an X-ray analysis was performed.

Notizen: Carbocycles from monosaccharides. III. Concerning the diastereoselective formation of cyclopentane derivatives. Transformations in the galactose series.The diastereoselectivity of the intramolecular nitrone-olefine cycloaddition of 1, 3 and 4 (Scheme 1), yielding only 2, 5 and 6 but none of the isomers 8, 9 and 10 is explained by assuming a kinetic control and postulating that the relative activation energies of the two relevant transition states in the cyclization of e.g. 1 can be estimated from the conformers A and B, the latter being destabilized by a synperiplanar arrangement of the nitrone function and the 2-alkoxy-group (Scheme 2). It is further postulated, that this destabilization is responsible for the formation of (2,3)-trans configurated products. Since 2, 5 and 6 are presumably thermodynamically more stable than 8, 9 and 10, a case was investigated, where the cycloaddition can either give thermodynamically less stable (2,3)-trans-product such as 12 or a thermodynamically more stable (2,3)-cis-product such as 13. 12 and 13 could both be formed from the aldehyde 25 via the nitrone 11 (Schemes 3 and 5). Treatment of the galactoside 16 first with Zn in aqueous butanol (forming among other products 25 and its 2-debenzyl-oxy-derivative) and then with N-Methyldroxylamine yielded the isoxazolidines 12 (72%), 13 (2%) and 27 (7%) (Schemes 4 and 6). Similarily, the anomeric silylated galactosides 17 and 23 gave 29 (78% from 17, 77% from 23) and 27 (5% and 3%). Upon desilylation, 29 gave 32, which was converted into 12. The structure of the isoxazolidines was unambiguously deduced from their NMR. spectra and those of their derivatives 33 and 34. Compound 32 was further transformed into its deoxyderivative 36. The high diastereoselectivity of the cycloaddition restricts the number of diastereomeric, pentasubstituted cyclopentanes available by this method. However, cyclization of the 2-Hydroxy-aldehyde 37 (Scheme 8) gave the kinetically less favoured isomer 40 in a higher proportion, showing the differential influence of hydrogen-bonds on the relevant activation energies. Thermolysis of 32 gave 40 (79%) and 41 (11%). The structure of 41 was deduced from its NMR. spectra and those of its derivatives 42 and 43. Thermolysis of 29 gave, after desilylation, 41 (42%), 40 (22%) and 32 (13%) and thermolysis of 6 lead to a 25 : 75 equilibrium with 44 (combined yield 90%). These transformations illustrate means leading to additional isomers and are in agreement with the proposed explanation of the diastereoselectivity in question.

Notizen: The absolute configuration of verrucarin B (2) has been determined by a single crystal X-ray diffraction analysis. This result permits the stereochemistry of the biogenetic transformation of mevalonic acid (12) to verrucarinic acid (7) to be deduced.

Notizen: Aus den Wurzeln der im Titel genannten Labiate wurde Crocetin-dialdehyd (8,8′-Diapo-carotin-8,8′-dial) (1), C20H24O2, isoliert. Chromatographisch wurde diese Verbindung auch in den oberirdischen Teilen dieser Pflanze nachgewiesen.

Notizen: Iridoidglucosides from Leucocarpus perfoliatus G. DON.The known iridoid glucoside boschnalosid (1) was isolated from Leucocarpus perfoliatus in addition to the hitherto unknown yuheinosid, for which structure 2 was deduced.

Notizen: Simple Synthesis of 6-[4-Methyl-3-cyclohexen-1-yl]-5-hepten-2-on, a Precursor of α-Bisabolene and Its Isopropenyl IsomerThe alcohol 14 reacts with vinyl resp isopropenyl ether by Claisen rearrangement to give the aldehyde 16/17 resp. the ketone 3/4. Contrary to other reports this separable (E/Z)-mixture also occurs as a result of the synthesis following the pathway 7 → 8/9 → 10/11 → 12/13 (see also [2]). The bisabolene isomers 5 resp. 6 are obtained by reaction of 3 resp. 4 with methylidene triphenyl phosphorane. A mixture of 1 and 5. however, is formed from 3 via the alcohol 18 and its acetate 19. Likewise 4 reacts via 20 and 21 to give a (2/6)-mixture.

Notizen: Contribution to the Absolute Configuration of the Spermine Alkaloids O-Methylorantine and AphelandrineThe absolute configuration of the spermine alkaloid O-methylorantine (1) isolated from Chaenorhinum minus (L.) WILLK. ET LGE. and Ch. villosum (L.) WILLK. ET LGE. was determined. Besides the difference in the substitution at C(31) (OCH3 versus OH) the constitution of 1 and aphelandrine (2) [6] is the same. This was established by spectroscopic evidence, by isomerization reactions of 2, orantine (4) and their derivatives (Scheme 2), and by degradation reactions of 1 and 4, respectively. The methyl ether 1 of orantine (4), the latter prepared by base catalyzed isomerization from aphelandrine (2), is in all respects identical with the natural O-methylorantine (1). Orantine (4) is identical (UV., CD., 1H-NMR. and TLC. evidence) with ephedradine A, recently isolated by Hikino et al. [8], who determined the absolute configuration of ephedradine A by X-ray analysis. The absolute configuration of aphelandrine (2) was related to the one of 4 by chemical degradation.

Notizen: The course of the catalytic hydrogenation and isomerization (H2/Raney-Ni/dioxane or H2/Pd/C/EtOH) of Δ5.7-, Δ7-, Δ8-, and Δ8(14)-steroid olefins was shown to depend strongly on the configuration at C(13). The known hydrogenation/isomerization of reactions of Δ5.7-dienes in the 13β-series to Δ7-(H2/Raney-Ni/dioxane) and Δ8(14)-olefins (H2/Pd/C/EtOH) were also confirmed in the 3β, 19-epoxy-13β- and 3-Oxo-19-acetoxy-13β-steroid series (e.g. 32 → 35 → 37, Scheme 3). On the other hand, in the corresponding 13α-steroid series the same reactions afforded the Δ7-. and the Δ8-olefins (mixture of products with H2/Raney-Ni/dioxane; quantitatively the Δ8-compounds with H2/Pd/C/EtOH; s. e.g. Scheme 3). A similar dependence on the C(13) configuration was observed in the allylic oxidation of these olefins with SeO2 (Fieser's test, see Table), and in the acid catalyzed opening of the 7α, 8α-epoxides (e.g. 60 → 62 + 63 in the 13β-series, and 56 → 64 + 65 in the 13α-series, Scheme 8).

Notizen: Stereospecific syntheses of (E)- and (Z)-α-bisabolenes have made revision of the configuration of natural (+)-α-bisabolene from Opoponax oil necessary. 13C-NMR. spectroscopy has been used for the differentiation of these isomers.

Notizen: Some Irradiation Experiments with 2, 1-Benzisothiazoles2, 1-Benzisothiazole (1) on irradiation with a mercury high-pressure lamp in benzene/diethylamine yields, after acetylation, 2-acetylamino-benzaldehyde (3; Scheme 1). Similarly, irradiation of 3-chloro-2, 1-benzisothiazole (2) in benzene/diethylamine leads to a mixture of 3-dimethylamino-2, 1-benzisothiazole (6a) and N, N-diethyl-thioanthranilamide (7a; Scheme 2). Benzisothiazole 6a, on irradiation, is not transformed into 7a. On the other hand, when 2 is irradiated in methanol a mixture of 3-methoxy-2, 1-benzisothiazole (4a) and methyl anthranilate (5a; Scheme 2) is obtained. In this case, 4a on irradiation in methanol or ethanol also yields 5a. No exchange of the methoxy group in 4a is observed when the irradiation is performed in ethanolic solution. Thus, 2, 1-benzisothiazoles 1, 2 and 4a react photochemically by N,S-bond cleavage and hydrogen-atom abstraction from the solvent (Scheme 3). 3-Chloro-2, 1-benzisothiazole (2) shows a second photoreaction, i.e. nucleophilic exchange of the chloro substituent by methanol or diethyl amine. The latter reaction can also be observed thermally, e.g. in boiling methanol in the presence of methoxide ions.

Notizen: Structure of Sesquiterpenes of Petasites hybridus (L.) G. M. et SCH.: Derivatives of NeopetasolThe structure of 5 compounds of the sesquiterpene fraction of petasites hybridus has been determined by combination of spectroscopic methods, especially by analysis of the 360-MHz-1H-NMR. spectra. Most natural products are esters of a sesquiterpene alcohol, which is the 7 β-epimer of petasol. The alcohol is named neopetasol.

Notizen: Hydroxide-Promoted Dehydrohalogenation of vic-Dihalides under Heterogeneous Conditions: Control Over the Reaction Outcome Due to Surprising Solvent and Metal EffectsSelective elimination of either one or two molecules of hydrogen halide from vic-dihalides can be conveniently achieved by employing solid sodium or potassium hydroxide in the presence of solvents such as glycol dimethylether or tetraethyleneglycol dimethylether.

Notizen: A novel iridoid glucoside, named globularidin, lacking the typical double bond between C(3) and C(4), has been isolated from the whole plant of Globularia alypum by the combination of open column- and high-performance liquid chromatography. The structure of this compound was established by chemical transformation and spectral data.

Notizen: Thermal Rearrangement of 2-Oxa-bicyclo [3.3.1]-non-7-en-3-ones; a Novel Lactone RearrangementLactone (+)-2 was prepared by iodolactonisation and subsequent elimination in 51% yield from the known acid (+)-1 (Scheme 1). Alkylation of (+)-2 furnished (+)-3a, (+)-3b and (+)-3c, respectively (Scheme 2). Heating of (+)-3a in boiling DMF racemized the compound ((+)-3a ⇆ (-)-4a). Heating of (+)-3b and (+)-3c, respectively, equilibrated them with (-)-4b and (-)-4c, respectively. This results are interpreted as a [3.3]-sigmatropic rearrangement with a transition state as depicted in a.

Notizen: Oxygen is generated when aqueous solution of iron (III) tris(2,2′-bipyridyl), Fe(bipy)33+, are brought in contact with catalytic amounts of powdered or colloidal RuO2. The oxygen yield depends strongly on the pH, reaching a maximum between pH 7 and 8 where it corresponds to the stoichiometry of the reaction: The rate of the reaction is so fast that it occurs practically upon dissolution of Fe(bipy)33+ in the aqueous phase. In acidic media (pH 4), no O2 evolution is observed. Instead, Fe(bipy)33+ is converted to an intermediate which in the presence of RuO2 yields O2 upon neutralization.The pH profile of the O2 evolution occuring upon illumination of Ru(bipy)32+ in the presence of the cobalt complex [Co(NH3)5Cl]2+ was also investigated.The surprisingly low energy losses (160 mV) in reaction (1) makes the construction of four quanta water splitting systems feasible.

Notizen: Alkali cation complexation and bilayer transport by the bicyclic decapeptides S,S′-bis-cyclo-glycyl-L-hemicystyl-glycyl-glycyl-L-prolyl (1), S, S′-bis-cyclo-glycyl-L-hemicystyl-glycyl-glycyl-D-prolyl (2), S, S′-bis-cyclo-glycyl-L- hemicystyl-sarcosyl-sarcosyl-L-prolyl (3), and S, S′-bis-cyclo-glycyl-L-hemicystyl-sarcosyl-sarcosyl-D-prolyl (4) were analyzed according to structural, thermodynamic and kinetic criteria; valinomycin was used as a reference ionophoretic system.Structural analysis of peptide 3 with spectroscopic methods showed different conformational arrangements in the bicyclic system depending on its state of complexation. Circular dichroism indicated the presence of a multitude of conformations with differing helicities around the disulfide bridge in both free and complexed states.Thermodynamic analysis by microcalorimetry demonstrated a far lower cation selectivity among the synthetic peptides than displayed by valinomycin. Peptide 3 shows cation affinities of about two orders of magnitude higher than peptide 4, but still much lower than found for the complexes of valinomycin with K+ and Rb+. In contrast to the latter case, the complexation reactions of peptides 3 and 4 are driven by both enthalpy and entropy contributions. Neither peptide 1 and 2 nor the cyclic partial structures of all four peptides displayed significant cation complexation.A kinetic analysis of the K+-complexation by peptide 3 based on the microcalorimetry experiments showed far lower rates of cation exchange for the synthetic peptide than those reported for valinomycin. Transport studies with peptide 3 using artificial lipid bilayer membranes gave negative results. The apparent lack of ionophoretic properties of these synthetic peptides despite their considerable ability to form complexes with cations is discussed in terms of structural parameters.

Notizen: The defensive secretion of the nudibranch Phyllidia varicosa consists of two isocyanosesquiterpenes: the previously described 9-isocyanopupukeanane (1), and its 2-isomer (4), for which we report the structure and properties. The mixture originates with a sponge, Hymeniacidon sp., where it is produced in varying proportions. CD. measurements and X-ray diffraction data establish the absolute configuration of the two metabolites.

Notizen: Synthesis of some branched paraffins of high molecular weightSynthesis and properties of two series of branched paraffins of high molecular weight are described. In the course of the preparation of one of the starting materials the Wolff-Kishner reduction of a sterically hindered ketone, unstable in basic medium, has been elaborated.

Notizen: α-MSH was labelled at its tyrosine2 residue with tritium and iodine. Several synthetic routes were investigated by preparing 13 precursor or mode compounds and 4 different labelled products (via about 40 intermediates). Their melanotropic activity was determined with an in vitro frog skin assay and, for some of the compounds, with a tyrosinase assay. The tritiation was performed on [Tyr(I2)2]α-MSH by catalytic halogen/tritium exchange, yielding α-MSH of high specific radioactivity (34 Ci/mmol) and full biological activity. Iodination was studied in detail using five different techniques. An equimolar chloramine T procedure proved to be the most convenient and reproducible method, resulting in monoiodinated α-MSH containing 99% of the label in position 2. The biological activity was 50% that of α-MSH; the specific radioactivity, determined in a competitive binding assay with a highly specific α-MSH antiserum and [Tyr(I)2]α-MSH as competitor, was 1530 Ci/mmol. The labelling techniques and the bioligical results are discussed.

Notizen: Leucine9-α-melanotropin ([Leu9]α-MSH) was synthesized in homogeneous solution by a fragment condensation approach, and it was assayed for its melanophore-dispersing and its tyrosinase-stimulating activity with a reflectometric in vitro frog skin assay and with cultured mouse melanoma cells, respectively. In both assay systems, parallel log dose-response curves were obtained for ([Leu9)]α-MSH and α-MSH; however, in the frog skin assay the activity of the title compound was 1 middot; 1010 Units/mmol, i.e. 25% of the activity of α-MSH, whereas its tyrosinasestimulating potency was only 1% compared to α-MSH (EC50= 2.5 · 10-7M). This indicates a major difference in the recognition/stimulation process of the receptors of the two cell types.

Notizen: 2-Pyridine sulfenyl chloride (PS-Cl) is a useful reagent for simultaneously deprotecting and activating the mercapto-group of cysteine and of cysteine-peptides preliminary to disufide-bond formation. The S-protecting groups that are amenable to this reaction include trityl, diphenylmethyl, acetamidomethyl, t-butyl, and t-butylsulfenyl.

Notizen: Attempted Synthesis of Nonafulvenes and of NonaheptafulvaleneThe reaction of cyclononatetraenide with α-bromobenzyl acetate (6) as well as with 1,1-dihalodimethylether gives at -50°, instead of the expected cyclononatetraenes, bicyclo[6.1.0]nona-2,4,6-triene derivatives 10d and 16 (Scheme 3 and 5, respectively). It seems that in some cases the well known thermally disrotative valence isomerization of cyclononatetraenes 7 to 3a, 7a-dihydroindenes 8 is much slower than the formation of bicyclo[6.1.0]nona-2,4,6-trienes of the type 10 and 16. This type of reaction hurts the Woodward-Hoffmann rules.Possible precursors of the attractive nonaheptafulvalene are prepared by reaction of acetoxy-tropylium fluoborate (19a) as well as of bromo-tropylium bromide (19b) with lithium-cyclononatetraenide (Scheme 8). So far, the attempted gas-phase pyrolysis of the precursors 21a and 21b failed to give nonaheptafulvalene (5).

Notizen: Kinetic Study of the Distribution of Electrically Neutral Ionophores between a Solvent Polymeric Membrane and an Aqueous PhaseThe kinetic behaviour of a series of ligands in the transfer from a solvent polymeric membrane into a stirred aqueous phase was investigated and compared with theoretical kinetic models. It was found that the transfer of ligands with low lipophilicity was controlled by the diffusion in the membrane phase, and that of ligands with high lipophilicity was controlled by the exchange reaction at the phase boundary and/or the diffusion through the unstirred Nernst diffusion layer. The diffusion coefficients in the membrane decrease drastically on increase of the content of the polymer in the membrane and are nearly independent of the size and lipophilicity of the ligand, whereas the overall transfer coefficient through the boudary region does not depend on the polymer content but decreases with increasing lipophilicity of the ionophore.

Notizen: Preparation of Stilbenyl Derivatives of IsoxazolesSchiff's bases derived from 3- and 5-(p-formylphenyl)-phenylisoxazoles and o- or p-chloroaniline are reacted with various p-tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t-but-oxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). 5-[4-(Chlorphenylimino-methyl)phenyl]-phenylisoxazoles react less readily than the corresponding 3-isomers.

Notizen: Synthesis of a 33-membered Polyaminolactam by Use of the Zip-reactionThe pentaamino lactam derivative 11 was synthesized from the 13-membered tosylaminolactam 2. The prolongation of the side chain was achieved using the phthalimido derivative 3. After removal of the protecting groups the resulting base 11 was treated with KAPA reagent (1,3-propanediamine/potassium-3-aminopropyl-amid). By zip-reaction the 33-membered 13, 17, 21, 25, 29-pentaaza-32-dotriacontanelactam (1) was formed in 85% yield.

Notizen: Influence of imidazole, metal salts and mixtures of imidazole/metal salt on ‘prebiotic’ condensation reactions induced by polyphosphates in aqueous solutionsIn the presence of imidazole, aqueous solutions 0.1 M in glycine and 0.1 M in sodium trimetaphosphate, at pH 8.0-8.6 and room temperature, yield after 14 days up to 3% of triglycine. Addition of Cd2+ or Zn2+ decreases the yields, while Mg2+ increases them slightly.The significance of the systems trimetaphosphate/imidazole and trimetaphosphate/imidazole/magnesium salt in the promotion of ‘prebiotic’ condensation reactions in aqueous solutions, especially the condensation of amino acids, is discussed.

Notizen: Synthesis of 3β-acetoxy-24-aza-24-desoxa-xymalogeninStarting from the pregnenolone-derivative 1 we report the synthesis of the possibly cardiac-active compound 24-aza-24-desoxa-xysmalogenin 15.

Notizen: Cynaratriol, a new guajanolide from Cynara cardunculus L. and C. scolymus L. (Compositae)A new guajanolide given the name cynaratriol (4) was isolated from the leaves of Cynara cardunculus L The structure of 4 and its derivatives 3, 11, 13-triacetylcynaratriol (5) and 3, 13-dibenzoyl-cynaratriol (6) was deduced on the basis of IR.-, 1H-NMR.-, 13C-NMR.- and mass spectroscopic data. 4 is also present in C. Scolymus L. as shown by GC./MS. analysis. The same absolute configuration is suggested for 4 as found for all other Cynara sesquiterpenes.

Notizen: Benzimidazole and benzothiazole sugar derivativesSimple aldehydosugars such as 1 or 2, by reaction with o-phenylenediamine, gave the corresponding benzimidazoles 3 and 4. Whereas the unperturbed α, β-unsaturated aldehydosugar D gave the benzodiazepine E upon treatment with o-phenylenediamine, the formyl-bearing alkenyl acetals 5 and 8 led, in the same conditions, to the benzimidazoles 6 and 9 respectively or, on reaction with o-aminothiophenol, to the benzothiazoles 7 and 10 respectively. This difference in reactivity is explained by the electrondonor ability of the oxygen atom of the alkenyl acetal function as shown by the 13C-RMN. spectra.

Notizen: Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic estersTreatment of 3-O-benzyl (or 3-O-methyl)-1, 2-O-isopropylidene-α-D-xylo-pentodialdo-1, 4-furanoses (2 or 1) with acetylbromomethylidenetriphenylphosphorane (3), benzoylbromomethylidenetriphenylphosphorane (4) or bromoethoxycarbonylmethylidenetriphenylphosphorane (5) gave in good to excellent yields the expected enose (6--11). In all cases but one (8 where some 10% of the E-isomer was formed) the reaction led to the exclusive formation of the Z-isomer whose configuration was established by NMR.

Notizen: 24-Isopropycholesterol (1) and 22-dehydro-24-isopropylcholesterol 2 have been isolated as the only sterols from an Australian sponge of the genus Pseudaxinyssa. Structures have been deduced from spectroscopic data.

Notizen: Mixed acetals 7 of benzeneseleninylacetaldehyde, prepared by a simple 2-step procedure from mono- and bicyclic allylic alcohols 5, undergo benzeneselenenic acid elimination to transient ketene acetals 8 which afford γ, δ-unsaturated esters 9 via the ester Claisen rearrangement (Scheme 2). Under the same conditions selenoxide 7h derived from benzyl alcohol 5h is converted back to benzyl alcohol with the concomitant formation of ethylphenylselenoacetate 12.

Notizen: Thermal Cyclization of α-Alkynones to 2-CyclopentenonesGas phase thermolysis at 600-740° of substituted 1-pentyn-3-ones (α-alkynones), which are easily prepared by acylation of trimethylsilyl acetylenes, leads to substituted 2-cyclopentenones. The intramolecular formation of a new C, C-bond between an acetylenic and a non-activated carbon atom is accompanied by a [1,2]-migration of one of the substituents at the triple bond. This novel ‘-alkynone cyclization’ reaction may be explained by postulating an alkylidene carbene intermediate which inserts into a C,H-bond five carbon atoms away at the non-acetylenic part of the ketone. Several examples demonstrate that the α-alkynone cyclization offers a simple tool for the preparation of certain monocyclic, bicyclic and spiro compounds containing a 2-cyclopentenone moiety.

Notizen: 8-Benzoyl-9-deuterio-naphtho [de-2.3.4]bicyclo [3.2.2]nona-2,6,8-triene (1) rearranged quantitatively in a photochemical di-π-methane-type process to 2-, 6-, and 9-deuteriated 1-benzoyl-naphtho [de-2.3.4]tricyclo [4.3.0.02,9]nona-2, 6-diene (8a-c). The phenylhydroxymethyl analogue 2 underwent a similar regioselective rearrangement to 9a-c. The rearrangement 1 → 8a-c is proposed to proceed along three reaction paths evolving from two primary photochemical processes of naphthylvinyl and vinyl-vinyl bonding (1 → 3 + 6). Evidence for a competition between several paths and involvement of biradical intermediates derives from changes in the isotopomeric composition with temperature, and from laser flash detection (λexc 353 nm) of a transient. The dependence of the quantum yield for product formation from 1 on excitation wavelength and sensitizer triplet energy leads to the conclusion that reaction to the primary biradicals occurs directly from the S1 (n, π*) and T2 (n, π* ) states, and that reaction from T1 (π, π*) and from S2 (π, π*) proceed either directly or via T2.

Notizen: Formation of 4-, 5- and 6-membered heterocycles by ambidoselective cyclization of enolate anionsN-Acylmethyl-N-chloracetyl-2,6-dimethylanilines 4 were cyclized with base to 4-, 5- or 6-membered ring compounds, depending on the substituent R2 (Scheme 2). All products can be rationalized as derived from the intermediate enolate anions a and b. The enolate anion a reacts by intramolecular alkylation to yield either 1, 4-oxazines 5 or azetidines 6 (Schemes 1, 3 and 7). The regioselectivity observed is expected on the basis of the allopolarization principle. The enolate anion b reacts only with formation of a new C—C bond (Scheme 5). Comparison with the behaviour of the 2, 6-unsubstituted anilines 9, 1a and 12, shows a strong dependence not only on electronic but also on steric factors (Scheme 4 and 6).

Notizen: Bacteriochlorophyll aGg and Bacteriopheophytin ap in Photosynthetic Reaction Centers from Rhodospirillum rubrum G-9+In photosynthetically active reaction centers from Rhodospirillum rubrum G-9+, the magnesium complex bacteriochlorophyll a contains geranylgeraniol as the alcohol component, while the metal-free bacteriopheophytin a contains phytol instead. These pigments bacteriochlorophyll aGg (4) and bacteriopheophytin aP (1) were isolated from reaction center preparations in a ratio of 2:1 and (after demetallation of 4) identified as bacteriopheophytin aGg (2), and aP (1) by comparison with authentic samples (UV./VIS., CD. and mass spectra as well as mixed HPLC.).

Notizen: 1H- and 13C-NMR.-spectra of 6-(p-X-phenyl)fulvenesThe 1H- and 13C-NMR.-spectra of a series of 6-(p-X-phenyl)fulvenes 3, measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5-membered ring. Small changes in bond length are observed by comparison of the vicinal 1H, 1H-coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).

Notizen: Epoxidation of 3-phenoxycyclohexene 5 with m-chloro-perbenzoic acid gave 6 and 7 in a ratio of 9:1. These two epoxides were heated with a series of amines to give the aminophenoxycyclohexanol derivatives 1 and 2 respectively; in all cases the reaction was regio- and stereospecific. Two methods based on the principle of neighbouring group participation were developed to synthesize the cis-amino alcohols 3 and 4. In the first, the hydroxy group was used to introduce an amine function at the vicinal carbon atom. In the second method, the amino group served as the point of reference and the configuration of the adjacent alcohol function was inverted.

Notizen: Excitation of p-Chloranil (CA) in propylcyanide (PrCN) at room temperature leads to rapid production of 3CA* which decays predominantly to CAH· with kd0 = 1.6 · 105 s-1. Observation of a photoinduced current suggests simultaneous production of CA- formed by electron transfer quenching of 3CA* by the medium. Added naphthalene (NP) quenches 3CA* with kq = 7.0 · 109M-1S-1; NP+ is unambigously identified as product (besides CA-) of the electron transfer process. Dissociation of the ion pair occurs with essentially unit probability. Higher concentrations of NP lead to the formation of (NP)+2. Pertinent spectroscopic parameters established for NP+ under the conditions used are λmax = 685 nm (∊ = 2970) using the known parameters of CA\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} as reference. NP+ and CA\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} decay by charge annihilation with kr = 4.5 · 109 M-1S-1. The deviation from the diffusion controlled rate constant expected for ionic species, is discussed in view of the spin characteristics of the process. Comparison with two other ion recombination reactions leads to the conclusion that ‘inverted behaviour’ as expected from Marcus' theory does also not show up for backward e--transfer between two ions (produced by forward e--transfer between two neutrals). Residual absorptions in the system are ascribed to CAH·, tentatively proposed to originate from H+-abstraction by CA\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} from the solvent. NP+ appears to be a rather stable species with respect to the medium if the latter is meticulously purified.

Notizen: Because of its overall steric resemblance to the phenylalanine analogue, carboranylalanine, the title compound was prepared by the modified Strecker synthesis of Patel & Worsley. The use of (S)-(-)-α-methylbenzylamine in the synthesis, the positive trend of [α]D with increasing protonation, and the thin-layer chromatographic behaviour of synthetic diastereomeric dipeptides are strong indications that the configuration at the asymmetric carbon atom is S (natural L). Its optical purity was ascertained by purification via the quinine and ephedrine salts of t-butoxy-carbonyl-adamantylalanine. The new amino acid shall be used for studies of structure-activity relationships of phenylalanine and leucine residues in biologically active peptides. In addition, a convenient synthesis in excellent yield of the starting material, 2-(1-adamantyl)-ethanal, by Pfitzner-Moffat oxidation of 2-(1-adamantyl)-ethanol is described.

Notizen: N-Deacetylcolchiceine (7), readily available from colchicine (1), was converted into N-trifluoroacetyl-deacetylcolchiceine (8). Methylation of 8 with methyl iodide in the presence of potassium carbonate afforded a mixture of N-trifluoroacetyl-demecolcine (10) and its isomer 11. The mixture of 10 and 11 was detrifluoroacetylated and separated by chromatography to afford demecolcine (2) and isodemecolcine (12). A more practical route to 2 started with 8, and gave N-trifluoroacetyl-deacetylcolchicine (13) and its isomer 14 after O-methylation with diazomethane. N-Methylation of 13 and 14 with methyl iodide and potassium carbonate afforded 10 and 11. The overall yield in the conversion of colchicine (1) into demecolcine (2) via 7, 8 and 13 was 55%.

Notizen: Sugar triazenes and benzotriazinesSeveral triazenylsugars have been prepared, generally in good yields, by treating an amino sugar with a substituted benzenediazonium salt. The triazenylsugars bearing a hydrogen atom on the triazenyl group are acetylated on the nitrogen atom closest to the glycosyl moiety (N(1)), even when the proton exchanged sites between N(1) and N(3). When an acetyl or a methoxycarbonyl group was present in the ortho position of the benzene ring cyclization took place leading to a 3,4-dihydro-4-methylidene-1,2,3-benzo[d]triazine or a 3,4-dihydro-1,2,3-benzo[d]triazin-4-one respectively.

Notizen: Acetoxythallation of (-)-elemol acetate (1b) yields a diacetate 2b which after treatment with lithium aluminium hydride gives (-)-guai-1 (10)-ene-4α, 11-diol (2a). (-)-Elemol (1a) is converted to (-)-selina-4α, 11-diol (9, cryptomeridiol) by hydroxymercuration followed by reductive demercuration. (+)-γg-Elemene (5) similarly yields (+)-selin-7(11)-en-4α-ol (11, juniper camphor). The stereochemistry and mechanism of these metal salt-induced olefinic cyclization and their biogenetic implication are discussed.

Notizen: Antitumor showdomycin analoguesA series of 3-glycosylidenesuccinimides (3) and 3-glycosylidene-1-phenyl-succinimides (5) have been prepared in good yields using a Wittig reaction. In each case, the preponderant, or even the exclusive, isomer formed was E. As expected from orbital considerations, the contribution to the conformational equilibrium of the rotamer whose H—C (γ) and H—C(δ) bonds were antiparallel was low. One of these succinimide derivatives 3a showed interesting anticancer activity, similar to that of the sugar enone C. These compounds probably act as somewhat selective alkylating agents.

Notizen: Different lipophilic β-diketones have been prepared. Some preferably transport Mg2+ and Ca2+ through PVC-based liquid membranes when a pH-gradient is applied across the membrane. A theoretical model is presented that allows a description of potentiometrically determined ion selectivities as well as transport selectivities obtained under zero current and electrodialytic conditions, respectively. The expectations based on this model are in agreement with the experimental evidence presented. Some membrane systems have potentiality for their application in the measurement of water hardness.

Notizen: Methylmercury(II) transfer from two heterocyclic thiones to a wide variety of other ligands and the reverse reaction have been investigated by the temperature-jump method. The reactions are almost diffusion controlled, even when the free energy difference is negligible. The only exceptions are reactions to and from hydroxide. They are about hundred times slower than those with other ligands of comparable stability at zero free energy difference. This is in agreement with the behaviour of hydroxide in other methylmercury(II) exchange reactions. They follow an associative reaction mechanism. An empirical correlation of rate-and equilibrium-constants for atom transfer reactions is proposed. This equation shows some similarities to that of the Marcus type for atom transfer. However, the proposed equation not only describes reactions governed by an associative mechanism, but also those of dissociative type and cases between the two extremes.

Notizen: Carotenoid Glycosyl Esters. The Synthesis of Crocetin-di-(β-D-glucosyl) Ester. A New Method for the Selective Esterification of Unprotected β-D-GlucoseThe naturally occurring crocetin-di-(β-D-glucosyl) ester is easily synthesized by the reaction of crocetin-di-imidazolide or crocetin-di-(1,2,4-triazolide) and unprotected β-D-glucose in pyridine in presence of a base (Scheme 4). Under the described experimental conditions the esterification takes place exclusively at the anomeric C-atom and furthermore produces only the β-anomer. It is the first time that an unprotected carbohydrate has been used for the selective synthesis of glucosyl esters at the anomeric C-atom. This represents the major advantage of this new method.

Notizen: The bis(methylthio)benzenes 3a-3c are oxidized to the methylsulfinyl-methylthiobenzenes 4a-4c on a Pt-anode in good yields.

Notizen: The C,C-bond cleavage which occurs during chromic acid oxidation of t-butylphenylmethanol (1) and 1,2-diphenylethanol (2) to the extent of up to 67% is reduced to 3% for 1 and 13% for 2 when the reaction is run in acetone, and totally suppressed upon co-oxidation of the alcohols 1 and 2 with oxalic acid. Similarly, the yield of 7-norbornanone obtained from 7-norbornanol (7) is raised in going from acetic acid (24%) to acetone (41%) and approaches 100% in the co-oxidation. With the co-oxidation 5-endo-bicyclo [2.1.1]hexanol (3) is converted to the corresponding ketone in 54% yield. Mechanistic implications of these results are discussed.

Notizen: Carbocyclic Compounds from Monosaccharides. 1. Transformations in the Glucose SeriesA method for the preparation of pentasubstituted cyclopentanes from monosaccharides is presented, involving two crucial steps, viz. the reductive fragmentation of 5-bromo-5-deoxyglucosides (such as 10, 17 and 23, see Scheme 3) with Zn or butyl lithium yielding 5,6-dideoxy-hex-5-enoses (such as 11 and 24, see Schemes 3 and 4), and the subsequent cyclization of these hexenoses with N-methyl- or N-(alkoxyalkyl)hydroxylamines (via the corresponding nitrones) to form cyclopentano-isoxazolidines (see Scheme 2). Thus, the glucosides 17 and 23 were converted diastereoselectively and in good yields into the cyclopentano-isoxazolidines 27 and 45 (Schemes 5 and 7), which were characterized by their transformation into various derivatives. 27 and 45 were correlated through the common derivative 62. The configuration of the cyclization products were established by pyrolysis of the N-oxide 65 to the enol ether 67 (Scheme 10).

Notizen: The Bredt olefins bicyclo [3.3.1]non-1-ene (2), bicyclo [4.2.1]non-1 (8)-ene (3), and bicyclo [4.2.1]non-1 (2)-ene (4) react rapidly with 1,3-dipoles such as diazomethane, phenyl azide, and mesitonitrile oxide to yield mixtures of two regioisomeric cycloadducts 10, 11 and 12, respectively. On the contrary, cycloaddition to the comparable monocyclic 1-methyl-(E)-cyclooctene (5) is fairly regioselective. 2-Methylnorborn-2-ene (6) gives one isomer with mesitonitrile oxide (as do less strained olefins), but mixtures with diazomethane and phenyl azide. 1H-NMR. and 13C-NMR. spectra of the cycloadducts are reported. The results are discussed in the light of frontier molecular orbital theory.

Notizen: The aim of the paper is to elucidate the problem of the regular changes in the properties of f-elements represented by the double-double effect. It is pointed out that because of the half-filled shell and double-double effects the f-element properties cannot be plotted as a linear function of the L-quantum number, as suggested by Sinha [1][2].

Notizen: The anomeric effect as a conformation determining factor for 3-cyano-perhydro-1,2-benzoxazinesAn unusual population of conformer II is found by 1H-NMR. spectroscopy in the conformation equilibrium I⇄ II of 1b (Fig. 3) in which the non-bonding nitrogen electronpair is anti-periplanar to the C—CN bond. This finding is interpreted in terms of a generalized anomeric effect operating in the α-cyano-hydroxylamin-ether structural unit.

Notizen: Selective ionophores of extreme lipophilicity for liquid membrane electrodesLipophilic ionophores of the type diether diamides have been prepared. Their lipophilicity is up to 7 orders of magnitude higher than the one of the most lipophilic ion carriers used as selective components in liquid membrane electrodes reported so far. For such ion carriers of extremely high lipophilicity kinetic limitations of the carrier induced ion transfer between aqueous and membrane phase usually dominate and heavily disturb the electromotive behavior of the membrane electrode. These limitations are absent only in those cases where most of the lipophilic segments of the carrier may remain in the membrane phase while the segments with the coordination sites are exposed to the aqueous phase during the transfer process.

Notizen: The values nJ (195Pt, 14N) are shown to be measurable directly from the 195Pt spectrum for a variety of complexes containing nitrogen ligands. The sample temperature can play an important role in determining the width of the 195Pt signal. 195Pt chemical shifts for the complexes trans-[PtCl2(C2H4) (substituted pyridine)] have been measured. Methyl substitution at the 2- and 6-positions produces a relatively large downfield shift.

Notizen: Reactions of oxygenated cobalt(II) complexes. XII. A binuclear μ-peroxodicobalt(III) complex with a macrocyclic bridging ringXI: siehe [1].Singly bridged [(tren) (NH3) CoO2(NH3) (tren)]4+ reacts with excess tren by replacement of NH3 in cis-position to the peroxo group and formation of a new type of doubly bridged μ-peroxo complex. An X-ray structure determination of [(tren)-Co(O2, tren)Co(tren)] (ClO4)4 · 2 H2O showed that the additional tren forms a macrocyclic bridging ring. The conformation of the CoOOCo group is transoid with a dihedral angle of 20°. The crystals are monoclinic with space group P21/c. The lattice constants are a = 9,798, b = 26,385, c = 16,385 Å, β = 110,2° with four formula units in the cell. The final R value is 0,124. ClO4- anions are disordered.The reactions of [(tren)Co(O2, tren)Co(tren)]4+ in aqueous solution are compared with those of [(tren) (NH3) CoO2Co (NH3tren)]4+. In acidic solution the new complex mainly decomposes to CoII and O2. In alcaline medium the bridging tren is replaced by an OH bridge, forming the well characterized doubly bridged [(tren)-Co(O2, OH)Co(tren)]3+. Differing from the singly bridged bis (ammino) complex, the reactions of which show no pH dependency at all, the decomposition of the tren bridged complex is H+-catalyzed. The kinetic data have been interpreted as (i) preceding fast protonation step which is followed by a conformational change of the bridging ring, (ii) acid hydrolysis of a Co-μ-tren bond and (iii) fast cleavage of the Co-OO bond which is labilized by coordinated H2O.

Notizen: The preparation of the nucleophile trans-[RuCl(NO)(1)], where 1 is the bidentate ligand Ph2PCH2C18CH2PPh2, and of the five-coordinate species [RuCl(CO)(NO)(1)], [RuCl(CO)(NO)(Ph2PCH2Ph)2] and [RuCl(NO)(2)(1)] are reported.The crystal structure of [RuCl(CO)(NO)(1)] shows that the coordination around the metal atom is distorted trigonal bipyramidal with the phosphorus atoms in axial positions. The Ru—N—O bond angle is 142.8°. 1H- and 31P-NMR. and \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \nu $\end{document}NO IR.-data for the above complexes are reported and related to the coordination geometry.

Notizen: The rearrangement products obtained upon reduction of 1,6-methano[10]-annulene (1) and its 11-halogen derivatives have been studied by ESR. and, in part, by ENDOR. spectroscopy. These derivatives comprise 11,11-difluoro- (2), 11-fluoro- (3), 11,11-dichloro- (4) and 11-bromo-1,6-methano[10]annulene (5), as well as the 2,5,7,10-tetradeuteriated compounds 2-D4 and 3-D4. The studies of the secondary products in question have been initiated by the finding that the radical anion of 11,11-dimethyltricyclo[4.4.1.01,6]undeca-2,4,7,9-tetraene (12), i.e., the prevailing valence isomer of 11,11-dimethyl-1,6-methano[10]annulene, undergoes above 163 K a rearrangement to the radical anion of 5,5-dimethylbenzocycloheptene (14). A rearrangement of this kind also occurs for the radical anion of the parent compound 1, albeit only above 323 K. The lower reactivity of 1\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} relative to 12\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} is rationalized by the assumption that the first and rate determining step in the case of 1\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} is the valence isomerization to the radical anion of tricyclo[4.4.1.01,6]undeca-2,4,7,9-tetraene (1a). In the reducing medium used in such reactions (potassium in 1,2-dimethoxyethane), the final paramagnetic product of 1\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} is not 5H-benzocycloheptene (15), but the benzotropylium radical dianion (). This product () is also obtained from the radical anions of the halogen-substituted 1,6-methano[10]annulenes, 2 to 5, in the same medium. The temperatures required for the conversion of 2\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 3\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} into lie above 293 and 243 K, respectively, whereas the short-lived species 4\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 5\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} undergo such a rearrangement already at 163 K. The stability of the four halogen-substituted radical anions thus decreases in the sequence 2\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} 〉 3\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} 〉 4\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} ≈ 5\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}. Replacement of 2\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 3\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} by 2-D4\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 3-D4\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}, respectively, leads to 1,4,5,8-tetradeuteriobenzotropylium radical dianion (). Experimental evidence and theoretical arguments indicate that the rearrangements in question are initiated by a loss of one (3\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 5\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}) or two (2\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document} and 4\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}) halogen atoms. Such a reaction step must involve the intermediacy of the radical 19 · (see below) which rapidly isomerizes to the benzotropylium radical 16:. Support for the transient existence of 19. is provided by the thermolysis of 1,6-methano [10]annulene-11-t-butylperoxyester (6) which yields 16. in a temperature dependent equilibrium with a mixture of its dimers (162).In the hitherto unreported ESR. spectra of 2\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}. and 3\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}} $\end{document}, the coupling constants of the ring protons differ considerably from the analogous values for the radical anions of other 1,6-bridged [10]annulenes. These differences strongly suggest that the fluoro-substitution substantially affects the character of the singly occupied orbital.

Notizen: On ultraviolet irradiation of the cyclopent-2-enyl methyl ketones 1a-c at -54° ≤ t ≤ 139°, photo-CIDNP. effects of the starting ketones, the 1,3-acetyl shifted isomers (2), and radical disproportionation and combination products (4-7) were observed. These effects show a unique dependence of the polarization phase on temperature which is a novel feature in photo-CIDNP. studies. The results of the investigation, which also included experiments using triplet quenchers, triplet sensitizers and radical scavengers, are rationalized in terms of Schemes 2 and 3.α-Cleavage is a major excited-state reaction of 1a-c on direct irradiation. Temperature-activated α-cleavage (kaS(t)) to the radical pair R · · R′1 and intersystem crossing (kisc) to the T2 state are among the competing S1 deactivation processes. The T2 state in turn cleaves (kaT2) to R · · R′3 A ‘low-temperature range’ with kisc ≫ kaS(t) and a ‘high-temperature range’ with kaS(t) ≫ kisc exhibiting preferential reactivity from the T2 and S1 states, respectively, can be defined for all three β,γ-unsaturated ketones 1a-c.

Notizen: Spiro-β-lactams from [2+2]-Cycloaddition of Ketenes to IminolactonesIminolactones (‘Isoimides’) derived from maleic anhydride and amines are shown to react with various ketenes in a [2+2]-cycloaddition mode. Either preformed ketenes or the combination acid chloride/tertiary amine can be used as reagent. The reaction products have been assigned the spiro-β-lactam structure. Unsubstituted ketene is inert under the reaction conditions. It is possible to synthesize the spiro-β-lactams in a one-pot procedure, starting from a mixture of maleic anhydride/amine and excess dialkylketene.

Notizen: The disilane/disilylmethane rearrangement of an optically active disilanyl sulfide 9B was used to prepare an optically active disilylalkene 10 whose absolute configuration was established by X-ray analysis of the bromo derivative 13 (P21, a = 7.847 (3) Å, b = 9.487 (3) Å, c = 20.010 (8) Å, β = 82.28° (3), Z = 2). Acylation of 10 furnished an optically active ketone 14, which was degraded to 16, a compound of known absolute configuration. The enantiomeric excess of 10 was determined by alkylation with an optically active lithium compound and that of 14 by an optically active NMR.-shift reagent. The SE′ reaction 10 → 14 was thus shown to proceed with 94% (97% syn/3% anti) stereoselectivity.

Notizen: 1,3-Dihydroisothianaphthen-2,2-dioxide (1) was readily converted to the 1-substituted sulfones 3 by deprotonation and subsequent electrophilic attack (Scheme 3 and Table). The appropriate 1-alkenyl- and 1-alkenoyl-sulfones 3 on heating at 213° to 240° underwent SO2-extrusion to give, via the non-isolated (E)-quinodimethanes II (Scheme 1), polycyclic products such as 4, 6 and 7 in good yields (Schemes 4 and 5). On the other hand, thermolysis of the 1-alkenoyl-1-thioether sulfones 9 furnished mainly the isochromenes 10 (Scheme 6).

Notizen: Preparation of unsaturated sugars phosphonates using nucleophilic conjugate additionDifferent types of phosphorus nucleophiles underwent conjugate addition reaction with one of the branched-chain sugars 4, 5 or 11 the addition taking place either on the endo or the exo face of the furanose ring (or on both faces in the case of 11). The configuration at C(3) of these new phosphorus-bearing types of sugars as well as the configuration at the phosphorus atom of the cyclic phosphinates 9 and 10 was established by NMR. (3JP,H-C(2), 3JP,C(1)). Small amounts (7%) of the spiro enol phosphonate 16 were formed when 11 reacted with trimethyl phosphite.

Notizen: The position of the ‘Inclined W theory’, i.e., the linear correlation of the properties (Pi) of the lanthanide and the actinide ions with their ground state total orbital angular quantum numbers (L), Pi = wiL + ki, where wi and ki are the slopes and intercepts of the least squares lines, is made clear. The position of gadolinium is ambivalent, and it can be a common point for the symmetric ‘Inclined W plots’ or it may either belong to the second or the third tetrad depending on the system investigated. The propionate and the isobutyrate systems are used to elucidate the ‘Inclined W concept’. The ‘Inclined W parameters’ for the solvent extraction of the lanthanides with PMBP ligand have been calculated.