Bibliothek

Notizen: Synthetic application of epoxynitrones. II. Syntheses of steroidal α-methylidene-γ-lactonesThis communication describes the application of the epoxynitrone/CF3SO3SiR3 → 1,2-oxazine annelation-reaction [1] to the syntheses of steroidal α-methylidene-γ-lactones from olefines, e.g. 12 → 14a/b → 16a/b → 18a/b → 20 → 22 (Scheme 2).

Notizen: Evidence is presented which demonstrates that 13C-NMR. spectroscopy can be used with confidence in evaluating the configuration of R1R2CHOH centers at C(6) and C(8) of iridoid glucosides.

Notizen: XPS. and 1H-NMR. spectra of 1,3-diaryltriazenes complexes of Hg(II)The core binding energies C 1s, N 1s, Hg 4f7/2, Hg 4f5/2 in 7 symmetrical p-substituted 1,3-diphenyltriazenes complexes of Hg(II) have been measured by XPS. Within the limits of experimental error (± 0.2 eV) only one N 1s signal could be detected. This indicates the equivalence of the 3 N-atoms. Invariance of C 1s, N 1s, Hg 4f7/2, Hg 4d5/2 signals with the para substituents on the phenyl ring is explained on the basis of ionic character in the Hg, N bond. These results are corroborated by the 1H-NMR. spectra.

Notizen: Synthesis and reactivity of 3-aryl-1-(3,4-dimethyl-5-isoxazolyl)-triazenes and 4-arylazo-3,4-dimethylisoxazol-5-onesAccording to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5-amino-3,4-dimethylisoxazole (3) leading to either 3-aryl-1 (3,4-dimethyl-5-isoxazolyl)-triazenes (1A) or 4-arylazo-3,4-dimethylisoxazol-5-ones (4). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.

Notizen: The neurotoxin α-kainic acid (7) was synthesized from 1 via the thermal key step 5 → 6 in 41% overall yield.

Notizen: Stereospecific synthesis of 6β,7β-methylene-20-spirox-4-ene-3,21-dioneA stereospecific synthesis of the highly active 6β,7β-methylene-20-spirolactone 4 (Prorenone) is described.

Notizen: Chiral 2,2′-polyoxaalkano-9,9′-spirobifluorenesFrom 2,2′-diacetyl-9,9′-spirobifluorene (2), twelve chiral polyethers have been prepared as potential ion- and enantiomer-selective ionophores. The absolute configuration of the polyethers 15-17, 19-22, and 25 has been determined by chemical correlation with vespirenes [11] [29], by circular dichroism, and by X-ray analysis. The circular dichroism of 15-17, 19 and 21 depends on the size of the macrocycle and indicates that the fluorene chromophores of 19 and 21 with 13- and 16-membered rings respectively deviate considerably from orthogonality.

Notizen: Favorskii-rearrangement in the presence of 3,4-dimethoxyfuran: preparation of 3,4-dimethoxy 11endo-oxo-tricyclo [4.3.1.12,5]undec-3-en-10-one and any derivativesOn treatment with sodiumhydride of 2-chloro-cyclohexanone in the presence of 3,4-dimethoxyfuran, a possible intermediate of the Favorskii-rearrangement has been trapped as 3,4-dimethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undec-3-en-10-one (3). This new compound contains a highly nucleophilic double bond. It can be cleaved in high yield by ozonolysis to 2exo, 4exo-bis (methoxycarbonyl)-3-oxabicyclo [3.3.1]nonan-9-one (4). Addition of chlorine to 3 occurs in stereoselective exo-cis-manner to the crystalline 3exo, 4exo-dichloro-3endo,4endo-dimethoxy 11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (5). Silver ion assisted hydrolysis of 5, followed by thermal treatment of the intermediate hydrates, leads to the red 11endo-oxa-tricyclo [4.3.1.12,5]undecan-3,4, 10-trione (6), and methanolysis to 3,3,4,4-tetramethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (8). By photolytic decarbonylation, 8 is converted into 3,3,4,4-tetramethoxy-10-oxa-tricyclo-[4.3.12,5.0]decan (9).

Notizen: Activated quinones: O- versus C-addition of phenols. New regiospecific syntheses of xanthones, thioxanthones and N-methyl-9-acridonesThe acid catalyzed reaction of phenols with activated quinones, e.g. 2-methoxycarbonyl-1, 4-benzoquinone or 2-acetyl-1, 4-benzoquinone, leads to substituted biphenylderivatives (C, C-addition) as has been previously described [1]. O, C-Addition of phenols has now been achieved by using 2-methoxypyridin or 4-dimethyl-aminopyridin [4] as basic catalysts. The resulting substituted diphenylethers can serve as convenient starting materials for regiospecific syntheses of substituted xanthones, especially for 1, 4-dimethoxyxanthones.Arylthiols and N-methyl-N-arylamines also react readily with activated quinones to give substituted di-aryl-thioethers and N-methyl-N, N-diarylamines respectively; both types of compounds are convenient materials for regiospecific syntheses of substituted thioxanthones and N-methyl-9-acridones.

Notizen: Cob(I)alamin as Catalyst. 5. Communication [1]. Enantioselective Reduction of α,β-Unsaturated Carbonyl DerivativesThe cob(I)alamin-catalyzed reduction of an α,β-unsaturated ethyl ester in aqueous acetic acid produced the (S)-configurated saturated derivative 2 with an enantiomeric excess of 21%. The starting material 1 is not reduced at pH = 7.0 in the presence of catalytic amounts of cob(I)alamin (see Scheme 2). It is shown that the attack of cob(I)alamin and not of cob(II)alamin, also present in Zn/CH3COOH/H2O, accounts for the enantioselective reduction observed. All the (Z)-configurated starting materials 1, 3, 5, 7, 9 and 11 have been transformed to the corresponding (S)-configurated saturated derivatives 2, 4, 6, 8, 10 and 12, respectively. The highest enantiomeric excess revealed to be present in the saturated product 12 (32,7%, S) derived from the (Z)-configurated methyl ketone 11 (see Scheme 3 and Table 1). The reduction of the (E)-configurated starting materials led mainly to racemic products. A saturated product having the (R)-configuration with a rather weak enantiomeric excess (5.9%) has been obtained starting from the (E)-configurated methyl ketone 23 (see Scheme 5 and Table 2). The allylic alcohols 16 and 24 have been reduced to the saturated racemic derivative 17.

Notizen: Total Synthesis of Natural α-TocopherolTwo independent syntheses of (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl-methanol (8b), (Scheme 6 resp. 9) as optically active chroman moiety for the preparation of natural vitamin E via (S)-6-acetoxy-2,5,7,8-tetramethylchroman-2-carboaldehyde (2a) (Scheme 1) and a corresponding side chain are described. Both reaction sequences use trimethyl-hydroquinone as starting material; one approach employs an optically active C4 unit (10a) (Schemes 5 and 6) to introduce the required configuration at C(2), the other uses an optically active C5-synthon (11a) (Schemes 8 and 9) to build the optically active chroman unit. The correct configuration and optical purity of the chroman synthesized is established by correlation with optically pure material of known configuration from which natural vitamin E had already been derived [2].

Notizen: The crystal structure of the antibiotic hedamycin (1) has been solved by direct method and refined by least squares techniques to R = 0.091 for 2289 of 2643 independent reflexions. Crystals of C41H50N2O11 are orthorhombic, space group P212121 with lattice parameters a = 24.239 (12), b = 21.440 (10), c = 7.369 (4) Å, Z = 4. The structural features of hedamycin derived earlier by chemical and spectroscopical means are confirmed. Optical rotation and circular dichroism indicate that hedamycin (1) has the absolute configuration of the related antibiotic kidamycin (3). The conformation of ring F is a chair form with the aryl substituent almost axial. The bioxirane part of the antibiotic is in a synclinal conformation.

Notizen: Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-caroteneWittig-condensation of optically active azafrinal (1) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol (2) and (+)-(R)-α-ionol (5) leads to the crystalline and optically active carotenoid diols 4 and 7, respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9, respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].

Notizen: ESR. and ENDOR. studies are reported for the radical anions of 1,2-diphenylcyclopentene (3) and its di(pe+deuteriophenyl)-derivative (3-D10). Comparison of the coupling constants of the phenyl protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. with the analogous values for the radical anions of 1,2-diphenyl substituted cyclopropene (1) and cyclobutene (2) reveals regular changes in the sequence 1\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 2\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, which are caused by an increasing twist of the phenyl groups about the C(1), C(1′)- and C(2), C(1″)-bonds linking them to the ethylene fragment. Such a twist is shown to be also responsible for the large difference in the coupling constants of the methylene β-protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. (0.659 and 0.293 mT). It is suggested that - in order to minimize the losses caused by this twist in the π-delocalization energy - the 2 pz-axes at the centres 1 and 2 deviate from a perpendicular orientation to the mean plane of the cyclopentene ring. A deviation by 19° from such an orientation is required to account for the observed β-proton coupling constants in terms of their conventional cos2-dependence on the dihedral angles θ.

Notizen: Sorelline and Hobartine, Two New Indole Alkaloids from Aristotelia peduncularis (LABILL.) HOOK. F.From Aristotelia peduncularis (LABILL.) HOOK. F. two new indole alkaloids, sorelline (1) and hobartine (2), have been isolated. Their structures were elucidated on the basis of spectroscopic data (the formulae represent their relative configurations). The alkaloids 1 and 2 have closely related structures with a monosubstituted indole moiety and an unrearranged monoterpene unit in the aliphatic part.

Notizen: Synthesis and configuration of some spiro [indan-2,2′-pyrrolidine] and spiro [pyrrolidine-2,2′-tetraline] derivativesCatalytic hydrogenation of the nitrosoindan and nitrosotetralin derivatives 8 yielded trans-1-hydroxy-spiro [indan-2,2′-pyrrolidin]-5′-one (9) and trans-1′-hydroxy-spiro [pyrrolidine-2,2′-tetralin]-5-one (10) respectively, whilst the corresponding cis compounds 12 and 15 were prepared via the chlorides 11 and 14.The configurations of 10 and 13 were determined by X-Ray analysis.

Notizen: Reactions of valencepolaromeric ketenes of mesoionic heterocyles with 3-dimethylamino-2H-azirinesReactions of the 3-dimethylamino-2H-azirines 1a and 1b with the mesoionic oxazole 5 and the mesoionic dithiole 6 in acetonitrile at room temperature yield the 1:1 adducts 11, 12, 19 and 20, respectively (Schemes 5 and 8). These products can be formulated as adducts of the aminoazirines and the ketenes 5a and 6a, which are valence polaromeric forms of the mesoionic heterocycles 5 and 6 (Scheme 2).The structure of the adducts has been elucidated by spectral data and their comparison with the data of (Z)-11, the structure of which has been established by X-ray [19]. Oxidation of the 1:1 adducts with KMnO4 in a two-phase system yields 4-dimethylamino-3-oxazolin-2-ones (cf. Scheme 6) by clevage of the exocyclic C,C-double bond. A mechanism for the formation of the adducts is given in Scheme 9: Nucleophilic attack of 1 on the ketene leads to a primary adduct of type a, which undergoes clevage of the former N(1), C(2)-azirine bond to give adducts of type 11 or 19. The N(1), C(2)-ring opening of 1a in the reaction with ketenes contrasts with the N(1), C(3)-opening of 1a in the addition with, for instance, isothiocyanates. These different ring openings are explained by the difference in nucleophilicity of the heteroatoms X and Y in a′ (Scheme 10).

Notizen: The spironaphthalen-2-ones 2, 10 and 18 were prepared by N-bromosuccinimide (NBS) oxidation of 1, 9 and 17 respectively, whereas spironaphthalen-1-ones 24 and 25 were obtained by treating 23 with NBS.The stereoisomeric reduction products 29, 30 and 32 obtained from 24 and 25, gave the pentacyclic compound 33 on treatment with polyphosphoric acid.

Notizen: Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and DThe echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B (1) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-α-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C (2), C52H81N7O15, contains 3-hydroxyhomotyrosine in the place of 3, 4-dihydroxyhomotyrosine present in 1. Echinocandin D (3), C52H81N7O13, differs in two amino acids: 3, 4-dihyroxyhomotyrosine and 4, 5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine.

Notizen: Compounds 2, 5 and 9 represent the first examples of isolable dichlorooxiranes formed by formal addition of dichloro carbene to a carbonyl group under phase transfer conditions. On heating, 2, 5 and 9 rearrange into α-chloroacid chlorides 3, 6 and 10, respectively.

Notizen: Aminoisoxazoles C-nucleosidesUpon treatment with bromocyanomethylenetriphenylphosphorane, a series of aldehydosugar derivatives gave in good to excellent yields the corresponding terminal gem-bromocyanoenoses 3, 7-10 and 16. Reacted with hydroxylamine, these unsaturated sugars led to the expected [3] 5-amino-3-glycosylisoxazoles 4, 11, 12 and 17, whereas using hydroxyurea as a binucleophile they gave the corresponding 3-amino-5-glycosylisoxazoles 13 and 14 as previously described in other series [3]. The major interest of these compounds rests in their being close analogs (or enantiomers of analogs) of important biological compounds as f.e. AICAR.

Notizen: Irradiation of 4-Allylated 2,6-Dimethylanilines in Methanol4-Allyl-, 4-(1′-methylallyl)-, 4-(2′-butenyl)-, and 4-(1′,1′-dimethylallyl)-2,6-dimethylaniline (14-17; cf. Scheme 3) were obtained by the acid catalysed, thermal rearrangement of the corresponding N-allylated anilines in good yields. Aniline 14, when irradiated with a high pressure mercury lamp through quartz in methanol, yielded as main product 4-(2′-methoxypropyl)-2,6-dimethylaniline (22; cf. Scheme 4) and, in addition, 2,6-dimethyl-4-propylaniline (18) and 4-cyclopropyl-2,6-dimethylaniline (23). The analogous products, namely erythro- and threo-4-(2′-methoxy-1′-methylpropyl)-2,6-dimethylaniline (erythro- and threo-24), 2,6-dimethyl-4-(1′-methylpropyl)aniline (19), trans- and cis-2,6-dimethyl-4-(2′-methylcyclopropyl)aniline (trans- and cis-25), as well as small amounts of 4-ethyl-2,6-dimethylaniline (26), were formed by irradiation of 15 in methanol (cf. Scheme 5). When this photoreaction was carried out in O-deuteriomethanol, erythro- and threo-24 showed an up-take of one deuterium atom in the side chain. The mass spectra of erythro- and threo-24 revealed that in 50% of the molecules the deuterium was located at the methyl group at C(1′) and in the other 50% at the methyl group at C(2′) (cf. Scheme 6). This is a good indication that the methanol addition products arise from methanolysis of intermediate spiro[2.5]octa-4,7-dien-6-imines (cf. Scheme 7). This assumption is further supported by the photoreaction of 17 in methanol (cf. Scheme 8) which led to the formation of 4-(2′-methoxy-1′,2′-dimethylpropyl)-2,6-dimethylaniline (28) as main product. The occurrence of a rearranged side chain in 28 can again be explained by the intervention of a spirodienimine 31 (cf. Scheme 9). In comparison with 14, 15 and 17, the 2′-butenylaniline 16 reacted only sluggishly on irradiation in methanol (cf. Scheme 10). It is suggested that all photoproducts - except for the cyclopropyl derivatives which are formed presumably via a triplet di-π-methane rearrangement - arise from an intramolecular singlet electron-donor-acceptor complex between the aniline and ethylene chromophor of the side chain. Protonation of this complex at C(3′) or C(2′) will lead to diradicals (e.g. 33 and 34, respectively, in Scheme 11). The diradicals of type 33 undergo ring closure to the corresponding spirodienimine intermediates (e.g. 31) whereas the diradicals of type 34 take up two hydrogen atoms to yield the photo-hydrogenated compounds (e.g. 21) or undergo to a minor extent fragmentation to side chain degraded products (e.g. 30; see also footnote 7).-Irradiation of 4-ally-2,6-dimethylaniline (14) in benzene or cyclohexane yielded the corresponding azo compound 38 (cf. Scheme 12), whereas its N,N-dimethyl derivative 41 was transformed into the cyclopropyl derivative 42. The allyl moiety in 14 is not necessary for the formation of azo compounds since 2,4,6-trimethylaniline (39) exhibited the same type of photoreaction in benzene solution.

Notizen: Conjugated cyclic divinyl ketones containing fifteen and seventeen membered rings have been prepared in a single step by condensation of 1,3-bis (dimethylphosphono)-2-propanone (10) with the dialdehydes 14, 17, 20, and 42 in the presence of hydrogencarbonate in aqueous t-butyl alcohol at reflux without using high dilution techniques. The more highly unsaturated aldehydes give better yields and ketones 34 and 36, or mixtures of the two, were transformed to muscone (1) and Exaltone® by standard procedures. Civetone (2) was prepared by hydrogenation of 43 in pyridine solution. Dienone 29 appears to be the first α, β-unsaturated ketone in which one of the β-vinyl proton resonates at higher field than the corresponding α-proton.

Notizen: Mechanism of the Photochemical Addition of Methanol to 2-Allylated AnilinesWe studied in methanol the photoreaction of the 2-allylated anilines, given in Scheme 3 (cf. also [1]). Irradiation of N-methyl-2-(1′-methylallyl)aniline (15) with a high pressure mercury lamp yielded trans- and cis-1,2,3-trimethylindoline (trans- and (cis-34) as well as erythro- and threo-2-(2′-methoxy-1′-methylpropyl)-N-methylaniline (erythro- and threo-35; Scheme 7). When the corresponding aniline d3-15, specifically deuterated in the 1′-methyl group, was irradiated in methanol, a mixture of trans- and cis-d3-34, and of erythro- and threo-d3-35 was obtained. Successive dehydrogenation of the mixture of cis/trans-d3-34 by Pd/C in boiling xylene and by MnO2 in boiling benzene lead to the corresponding indole d3-36 (cf. Scheme 9), the 1H- and 2H-NMR. spectra of which showed that both cis-d3- and trans-d3-34 had bound the deuterium labeled methyl group exclusively at C(3). The 1H- and 2H-NMR. analyses of the separated methanol addition products revealed that erythro-d3-35 contained the deuterium label to at least 95% in the methyl group at C(1′), and threo-d3-35 to 50% in CH3—C(1′) and to 50% in CH3—C(2′) (cf. Scheme 9). To confirm these results 2-(1′-ethylallyl)aniline (16) was irradiated in methanol, whereby a complex mixture of at least 6 products was obtained (cf. Scheme 11). Two products were identified as trans- and cis-3-ethyl-2-methylindoline (trans- and cis-37). The four other products represented erythro- and threo-2-(1′-ethyl-2′-methoxypropyl)aniline (erythro- and threo-39) as major components, and erythro- and threo-2-(2′-methoxy-1′-methylbutyl)aniline (erythro- and threo-40). These results clearly demonstrate that the methanol addition products must arise from spirodienimine intermediates of the type of trans-9 and cis-11 (R1 = CD3 or C2H5, R2 = CH3 or H; Scheme 2) which are opened solvolytically with inversion of configuration by methanol. Thus, cis-11 (R1 = CD3, R2 = CH3) must lead to a 1:1 mixture of threo-13 and threo-14 (i.e.) a 1:1 distribution of the deuterium labelled methyl group between C(1′) and C(2′) in threo-35) The formation of erythro-d3-35 with at least 95% of the deuterium label in the methyl group at C(1′) indicates that trans-9 (R1 = CD3, R2 = CH3) reacts with methanol regioselectively (〉 95%) at the C(2), C(3) bond. Similarly, the formation of the methanol addition products in the photoreaction of 16 (Scheme 11) can be explained. Since the indolines, formed in both photoreactions, show no alteration in the position of the subsituent at C(1′) with respect to the starting material we suppose that the diradical 7 (R1 = CD3 or C2H5, R2 = CH3 or H; Scheme 2) is a common intermediate which undergoes competetive 1.3 and 1.5 ring closure yielding the spirodienimines and the indolines.This conception is supported by irradiation experiments with N, 3,5-trimethyl-2-(1′-methylally)aniline (17) and 2-(2′-cyclohexenyl)-N-methylaniline (18) in methanol. In the former case the formation of spirodienimines is hindered by the methyl group at C(3) for steric reasons, thus leading to a ratio of the indoline to the methoxy compounds of about 6.3 as compared with ca. 1.0 for 15 (cf. Scheme 12). On the other hand, no methoxy compounds could be detected in the reaction mixture of 18 (cf. Scheme 13) which indicates that in this case the 1.3 ring closure cannot compete with the 1.5 cyclization in the corresponding cyclic diradical of the type 7 (R1-C(1′)-C(2′) is part of a six-membered ring; Scheme 2).We suppose that the diradicals of type 7 are formed by proton transfer in an intramolecular electron-donor-acceptor (EDA) complex arising from the excited single state of the aniline chromophor and the allylic side chain. This idea is supported by the fluorescence specta of 2-allylated N-methylanilines (cf. Fig.1-4) which show pronounced differences with respect to the corresponding 2-alkylated anilines. Furthermore, the anilines 18 and 20 when irradiated in methanol in the presence of an excess of trans-1,3-pentadiene undergo preferentially an intermolecular addition to the diene, thus yielding the N-(1′-methyl-2′-butenyl)anilines 52 and 51, respectively (Scheme 15), i.e. as one would expect the diene with its low lying LUMO is a better partner for an EDA complex than the double bond of the allylic side chain.

Notizen: A new strategy for the synthesis of muscone (1) using the OH-assisted Prins reaction for macrocyclic ring closure has been developed. The monoacetal 4 of (Z,E)-4,8-dodecadienedial (3), easily obtainable from (Z,E,E)-1,5,9-cyclododecatriene (2), is treated with methallylmagnesium chloride, and the resulting C16-precursor 5 is subjected to acid-catalyzed cyclization in dilute (≤1%) solutions. This results in formation of the bicyclic dihydropyran derivatives 6 which directly yield muscone (1) on heating with a noble metal catalyst saturated with hydrogen. The five-step pathway proceeds with readily available starting materials in conventional steps and excellent overall yield (∼40%). This new principle of macrocyclic ring formation has also been used successfully for the preparation of 3-methylcyclotridecanone (34) and should be generally applicable for other suitable ring systems.

Notizen: A synthesis of (6 R, 7 R)-7-acylamino-2-oxocephem-4-carboxylic acids from penicillins is reported based on the formation of the 2-oxocephem system in an intramolecular Wittig condensation. An interesting steric effect of the acylamino grouping on the course of this key step was used to advantage. Some physical and biological properties of this new type of Δ3-cephem are described.

Notizen: The chiral aminoethers 1-4, accessible from tartaric acid, are tested as complexing ligands in organolithium reactions. The tetramine 4 turns out to cause highest inductions [see Table 2 and Equations (1)-(4)].

Notizen: Diglycosyl Derivatives. Preliminary communicationNovel types of diglycosyl compounds, some of them bearing a resemblance to natural di- or tri-saccharides are described: a diglycosyldiyne (1), a diglycosylthiophene (2), a diglycosylaziridine (3), a diglycosyldioxolane (4), as well as six C,N-diglycosylnitrones, 9b-9f and 14. These C,N-diglycosylnitrones, on treatment with an acetylenic Grignard reagent, led to the expected acetylenic diglycosyl-hydroxylamine 11, whereas diglycosylisoxazolines (f. ex. 10) were obtained when these nitrones underwent 1,3-dipolar cycloaddition to acetylenic compounds.

Notizen: Cob(I)alamin as Catalyst. 4. Communication. Reduction of α,β-Unsaturated NitrilesUsing catalytic amounts of cob (I)alamin and an excess of metallic zinc as source of electrons 1-naphthonitril (5) has been reduced to (1-naphthyl)methylamin (6) and in small amounts to (1-naphthyl)methanol (7) and (1,2,3,4-tetrahydro-1-naphthyl)methanol (8) (5 ½ h, CH3COOH/H2O; s. Scheme 3). Starting from cyclododecylideneacetonitrile (15) similar conditions (68 h, CH3COOH/H2O) produced the amines 16-19 as well as the nitrogen free saturated aldehyde 20, the corresponding allylic alcohol 21 and the saturated derivative 22 (s. Scheme 6). It is deduced that the first attack of cob (I)alamin on an α,β-unsaturated nitrile might occur on both the nitrile dipole as well as on the carbon atom in β-position. Cob (I)alamin in aqueous acetic acid saturates the isolated double bonds in allylic alcohols and amines. In a slow reaction the two different aromatic rings of (1-naphthyl)methanol (7) have been reduced giving the corresponding tetrahydronaphthalene derivatives 8 and 12, and in one case the production of the octahydroderivative 14 has been observed in a low yield (s. Scheme 5).

Notizen: The wavelength range of the CD. spectra of some cyclohexapeptides containing different sequences of glycine, L- and D-alanine is extended down to 170 nm. This allows a relatively complete recording of the (n - π*) and (π° - π*) Cotton effects. Some striking spectral changes are observed on going from one molecule to another. The relative influence of L- and D-alanyl residues is discussed: Some spectra may be qualitatively related to each other by considering the effect of an L-residue at position q in the ring to cancel partially with the effect of a D-residue at position q ± 3. Assuming these cyclopeptides to occur in a hydrogen-bonded pleated sheet structure, certain dominant changes in the spectra are interpreted as reflecting a transition of the overall backbone conformation from one which is closer to the (optically inactive) symmetry Ci to another which is closer to the (optically active) symmetry C2. An attempt is made to relate the influence of L- and D-substituents within hairpin bends of the pleated sheet structure to an amide sector rule.

Notizen: Lincomycin analogues. I. Chain-extensions of [1,2:3,4]-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranoseThe title aldehydosugar 1 treated with Wittig reagents led in good to excellent yields to the unsaturated sugar derivatives 3-7 and 10-15, 8 having been prepared by condensation of 1 with malonic acid. The configuration (Z or E) of each compound obtained has been established by 1H-NMR. These chain-extensions constitute the first synthetic step towards the preparation of lincomycin analogues.

Notizen: The photochemistry of optical active λ, δ-epoxy-enones. Racemization and cyclization of (-)-4-methylidene-5,6-epoxy-5,6-dihydro-β-ionone and of (-)-4-oxo-5,6-epoxy-5,6-dihydro-β-iononeUV.-irradiation (λ ≥ 347 nm as well as λ = 254 nm) converts the conjugated λ, δ-epoxy-enones (-)-2 and (-)-4 by cleavage of the C,C-oxirane bond to an intermediate ketonium ylide f which cyclizes giving the racemic starting materials. The degree of racemization depends on the length of the irradiation time.The formation of the optical active products (-)-3 and (+)-5 in these irradiations gives evidence, that the photocyclization of (-)-2 und (-)-4, respectively, is a one step reaction of a state g.

Notizen: The photoinduced cleavage of the C,C-oxirane bond of γ, δ-epoxy-enones: UV.-irradiation of 4-methylidene-5,6-epoxy-5,6-dihydro-β-iononeOn 1n, π*-excitation (λ ≥ 347 nm, pentane) 5 gives the isomeric bicyclic ether 10 in 75% yield (s. Scheme 2). In methanol the photoconversion of 5 to 10 is strongly reduced (12%) in favour of the formation of the methanol adduct 11 (43%). On photolysis in aqueous acetonitrile 5 is converted to the bicyclic ether 10 (9%), the dihydrofurane 12 (18%) as well as to the triketones 13A and 13B (7%), and 14 (23%).On 1π, π*-excitation (λ = 254 nm) in pentane no 10 is formed, but 5 isomerizes to the tricyclic cyclopropyl compound 16 (59%), the allenic product 17 (10%), and the cyclopropene compound 18 (12%; s. Scheme 3). Photolysis in methanol furnishes 11 (63%), and 18 (4%), but no tricyclic cyclopropyl compound 16. In a secondary photoreaction (λ = 254 nm) the dihydrofurane 12 is isomerized to the bicyclic cyclopropyl compound 20.Evidence is given that the products 11 and 13 are formed by solvent addition to an intermediate ketonium ylide b (s. Scheme 12). The presence of b is further proven by the formation of 12, a product of an electrocyclization of b. On photofragmentation of b carbenoids d and e are presumably formed (s. Scheme 14). 1,2-Hydrogen shift in d yields the allene derivative 17, and cyclization of d gives the cyclopropene compound 18. On the other hand, e cyclizes to the non isolated cyclopropene compound 69 which is transformed to 16 by an intramolecular [4 + 2]-cycloaddition.The present investigation shows that the photochemistry of 5 is determined by photoinduced C,C-bond cleavage of the oxirane ring. This is in sharp contrast to the photochemistry of conjugated γ, δ-epoxy-enones without the additional double bond in ε, ζ-position, where selective photocleavage of the C(λ), O-bond is observed.

Notizen: Enantioselective 1,2-addition of Li-, Mg-, Zn-, and Cu-organic compounds and of Li-enolates to carbonyl derivatives in the chiral medium DDBDDB = 1,4-Dimethylamino-2,3-dimethoxybutan (= 2,3-Dimethoxy-N,N,N′,N′-tetramethyl-1,4-butandiamin).The (+)-enantiomer of the methoxyamine DDB is used as a chiral cosolvent in the title reactions. As evident from the results listed in the table, enantiotopic faces are generally differentiated with preferences ranging from 55:45 to 60:40.

Notizen: The influence of twenty substituents R on the solvolysis rates and products of tertiary chlorides R - CH2CH2C(CH3)2Cl (7) has been studied. H, CH3, (CH3)2NCH2, ClCH2, Cl, CN and NO2 exert an inductive effect only, as the good correlation of the rates with the corresponding inductive substituent constants σIq shows. Bulkier alkyl groups, i.e. isopropyl and t-butyl, lower the rate due to a Baker-Nathan effect, while the n-electron donors CH3S, CH3O, HO and (CH3)2N and the σ-electron donors (CH3)3Sn and HOCH2 cause rate increases based on σIq constants. These accelerations are attributed to C,C-hyperconjugative and inductomeric effects which arise in the transition state for ionization. A comparison of the reactivity of the acyclic chlorides 7 and the corresponding 1-R-substituted 3-bromoadamantanes 1a shows that polar substituent effects are more strongly transmitted in the rigid bicyclic compounds 1a than in the flexible acyclic compounds 7.

Notizen: The intramolecular and dimensionless equilibrium constant, K′, for the equilibrium between open and aromatic-ring stacked isomers of ternary complexes formed between adenosine 5′-triphosphate, inosine 5′-triphosphate, or uridine 5′-triphosphate, Mg2+ or Zn2+, and L-tryptophanate, 2,2′-bipyridyl (bipy), or 1,10-phenanthroline (phen) have been estimated by 1H-NMR. shift measurements in D2O (I = 0.1M, NaNO3; 27°). The approximate equilibrium constants K′ are ≥ 20, ≥ 20, 1.2, 0.9, 0.7, 0.5, and 0.3 for the ternary complexes Zn (phen) (ATP)2-, Mg (phen) (ATP)2-, Zn (bipy) (ATP)2-, Zn (bipy) (ITP)2-, Zn (bipy) (UTP)2-, Zn (trp) (ATO) 3-, and Mg (trp) (ATP)3-, respectively. The percentages of the stacked isomers decrease in the order Zn (phen) (ATP)2- (≥ 95%) ≫ Zn (bipy) (ATP)2- (55%) 〉 Zn (bipy) (ITP)2- (48%) 〉 Zn (bipy) (UTP)2- (∼ 40%), which coincides with the order of stability of the binary metal-free adducts (phen) (ATP)4- 〉 (bipy) (ATP)4- ≃ (bipy) (ITP)4- 〉 (bipy) (UTP)4-; the corresponding stability constants are KABA = 28.2 ± 4.7, 8.1 ± 2.6, 8.8 ± 1.8, and ∼ 1 (M-1), respectively (D2O; I = 0.1 M, NaNO3; 27°): these series reflect the decreasing size of the aromatic-ring systems forming the stacks. The indole moiety of tryptophan resembles 2,2′-bipyridyl rather than 1,10-phenanthroline and K(trp)(ATP)(trp) = 6.2 ± 1.8 M-1 for (trp) (ATP)4-. Implications with respect to the stability of ternary complexes, and to biological systems are indicated briefly.

Notizen: Structural Modifications of Vitamin D3. Synthesis and Properties of the SO2-Adducts with (5Z)- and (5E)-Vitamin D3Treatment of (5Z)- and (5E)-vitamin D3 (4) with sulfur dioxide yields each quantitatively the cyclic sulfones 1a and 1b. Thermally induced elimination of sulfur dioxide leads to either isotachysterol3 (3) alone or mixtures of isotachysterol3 (3) and isovitamin D3 (2). On the other hand the extrusion of SO2 can be brought about by means of KOH/CH3OH or on an alumina surface affording (5E)-vitamin D3 (4). On treatment with CD3UD/tBuOK/D2O 1a and 1b are transformed (5E)-6, 19, 19′-trideuteriovitamin D3 (4a).

Notizen: (E)-3α-Acetoxy-5, 10-seco-1(10)-cholesten-5-one (3) was synthesized by fragmentation of 3α-acetoxy-5α-cholestan-5-ol (1) using the photochemical version [3] of the lead tetraacetate reaction [4], and transformed into the corresponding 3-oxo-compound (5). Two conformations (A2α and B1α) were deduced for the 10-membered ring of 3 by analysis of the 1H- and 13C-NMR. spectra in toluene. The major conformation (A2α) corresponds to that found in the solid state by X-ray analysis. According to its NMR. spectra in toluene, the medium-sized ring of the diketone 5 exists also predominantly in two conformations, the major one being analogous to A1β (the solid-state conformation of the 3β-acetoxy isomer (9) [1]) and the minor one to A2α (see above). The stereochemistry of the acidcatalyzed and thermal cyclisations of 3 as well as of the corresponding 5-oxime is discussed in terms of conformational factors.

Notizen: The crystal structures of PdCl2[(-)-DIOP], PtCl2[(-)-DIOP] and of NiCl2-[(-)-DIOP] have been determined by X-ray analysis and refined by least-squares methods [(-)-DIOP=(-)-2,2-dimethyl-4,5-bis(diphenylphosphinomethyl)-1,3-dioxolane]. The coordination around the nickel atom is tetrahedral, the coordination around palladium and platinum is square planar. The unit cell of the palladium complex contains two non-equivalent molecules with different conformations of the seven-membered chelate ring involving the metal and the two phosphorus atoms. PtCl2[(-)-DIOP] is isostructural with the corresponding palladium complex.

Notizen: 1H-NMR. Spectroscopic Determination of Enantiomeric Purities of Allenic Esters Using Optically Active Europium Shift ReagentsThe racemic allenic methyl esters 3--7 and the racemic allenic diesters 8--10 (cf. Scheme 2) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) and CCl4 in the presence of optically active tris[3-(heptafluorobutyryl)-(+)-camphorato]europium(III) (Eu(hfc)3) have induced unlike 1H-NMR. shift differences (ΔΔδ) for the protons of the methoxycarbonyl groups of their enantiomers. In some allenic esters the shift reagent causes additional separation of resonance signals; thus, further substituents on the allenic framework may be differentiated in the racemic mixture. This finding provides a widely applicable method for the determination of absolute enantiomeric purities of allenic esters and their corresponding acids. Accordingly we found for optically pure (+)-(S)-2-methyl-2,3-pentadienoic acid ((+)-(S)-13; cf. Fig. 2) a calculated [α]58920 value of + 73.3 ± 1.8°. Finally, the substituent effects on ΔΔδ-values (cf. Table 1--3) are discussed.

Notizen: Stereospecific Fragmentations in the Mass Spectra of Cyclohexanediamines and Bis(aminomethyl)cyclohexanesThe mass spectral behaviour, especially loss of NH3, of the six isomeric cyclohexanediamines 1--3 (cis and trans each, Scheme 1) as well as of the six isomeric bis(aminomethyl)cyclohexanes 4--6 (cis and trans each, Scheme 6) has been investigated. The cis- and trans-compounds of the 1,2-isomers 1 and 4 show very similar spectra, because of the ease of ring cleavage at C(1)--C(2) and the similar geometrical relations in all ring conformations. The cis- and trans-compounds of both the 1,3- and 1,4-isomers 2, 3, 5 and 6 show striking differences in their mass spectra due to stereospecific elimination of NH3 from the molecular ion.

Notizen: The Mass Spectral Decomposition of Isomeric Diacetamido-cyclohexanes, their N-Phenethyl-Derivatives and Bis(acetamidomethyl)cyclohexanesIn the mass spectra of the six isomeric diacetamidocyclohexanes 2--4 (cis and trans each, Scheme 2) as well as of the six isomeric bis(acetamidomethyl)cyclohexanes 6--8 (cis and trans each, Scheme 5) are clear differences between the constitutional isomers, whereas cis/trans isomers show very similar spectra. The lack of stereospecific fragmentations is explained by loss of configurational integrity of the molecular ion before fragmentation.However, the mass spectral fragmentation of epimeric diamidocyclohexanes becomes very stereospecific by the introduction of a phenethyl group on one of the nitrogen atoms: this group avoids epimerization of the molecular ion prior to fragmentation. In the N-phenethyl derivatives 10, 11, 13 and 14 (Scheme 8) the typical fragmentations of the cis-isomer after loss of ·C7H7 from the molecular ion are the elimination of CH2CO by formation of cyclic ions, and the loss of p-toluenesulfonic acid or benzoic acid, respectively, with subsequent elimination of CH3CN (Scheme 9). In the trans-isomer the typical fragmentations are the loss of the side chain bearing a tertiary nitrogen atom, and the elimination of the tosyl or benzoyl radical, respectively, with subsequent loss of CH3CONH2 (Scheme 10).

Notizen: The potentiometric study of the complexation of Cu2+ with 1,4,7-triazacyclononane (1), 1,4,8-triazacyclodecane (2) 1,5,9-triazacyclododecane (3) has shown that CuL, CuL2 and (CuLOH)2 are the main species present in solution. Their stabilities (Table 1) and their absorption spectra (Table 2) indicate facial coordination of the cyclic triamines in a distorted octahedral geometry.The formation and dissociation kinetics have been measured by stopped-flow techniques. The formation in acetate buffer can be described by the reaction of Cu2+ and CuAcO+ with the monoprotonated species of the ligand. The bimolecular rate constants for these complexations (Table 3) decrease when the ring size increases. In contrast the dissociation induced by acid is only little affected by the ring size. Thus for these complexes the rate of formation and not that of the dissociation determines the overall stability.

Notizen: The absolute configuration of the title compound, a minor constituent of civet, is shown to be S,S.

Notizen: Synthesis of 22,23-methano-24-nor-cholest-5-en-3β-ol and comparison with cystosterol22,23-Methano-24-nor-cholest-5-en-3β-ol, a novel cyclopropane-containing sterol was synthesized from stigmasterol and found to be different from the isomeric, naturally occurring marine sterol cystosterol.

Notizen: The synthesis of the spin-labeled uridine and 2′-deoxyridine analogues RUGT 2, DUGT 3, l-RUGT 4, and l-DUGT 5 is described. DUGT 3 showed some activity against the leukemia P388 cell line.

Notizen: The unique stabilization of the ester link in dialkyl succinyl succinates is explained and a facile route to known as well as to hitherto inaccessible succinyl succinates is suggested. New representatives of this series are described.

Notizen: The kinetics of ethylene oxidation by air over a supported silver catalyst were investigated in the temperature range 490-620 K. The reaction network was found to be triangular. Under virtually constant oxygen partial pressure (0.2 bar), the following rate relationships, (in mol g-1s-1) were found: (formulae in curved brackets denote partial pressures) where R is expressed in J · mol-1 · K-1.The given rate expressions are discussed in the framework of earlier kinetic investigations.

Notizen: Enantioselective 1,4-additions of organometallic compounds to conjugated systems in the chiral medium DDBDDB = 1,4-Dimethylamino-2,3-dimethoxybutan (= 2,3-Dimethoxy-N,N,N′,N′-tetramethyl-1,4-butandiamin).The chiral methoxyamine DDB is used as a cosolvent to add achiral Li-, Cu-, and Zn-organic compounds enantioselectively to prochiral β-carbon atoms of α, β-unsaturated aldehydes, ketones, nitro compounds and ketene-thioacetals (Tables 1 and 2). The selectivity generally ranges from 55:45 to 63:27, in one case (9b) an enantiomeric excess of 43% was obtained.

Notizen: The study of 16, 17, 18, 19, 28, 29-hexahydrorifamycin S by 1H-NMR. spectroscopy using INDOR at 100 MHz and homodecoupling at 270 MHz has shown that the conformation of the ansa fragment C(20)-C(27) and the position of this fragment relative to the naphthoquinone chromophore are practically the same as those of rifamycin S. This finding rules out the hypothesis that the lower activity of the hydrogenated rifamycins could be due to a different conformation.

Notizen: Pyrazolo[1,5-a]indolesTreatment of 1-(2-heteroaroyl or aroyl-phenyl)-pyrazoles (3) with potassium hydroxide in 95% ethanol or with sodium ethanolate in ethanol produces a novel ring closure to new 4-hydroxy-4-(4-heteroaryl or aryl)-4H-pyrazolo [1,5-a]indoles 5 and 6 (Table 1). A 2, 3, or 4-pyridyl at position 4 is easily reduced yielding the 4-(2, 3, or 4-piperidyl)-derivatives 7 and 8 (Table 2). Water is split off from these piperidyl-derivatives 7 or 8 to give the piperidylidene derivatives 9 or 10 (Table 3) which may be considered as heterocyclic analogues to known tricyclic psychopharmaceuticals with antidepressant or neuroleptic activities.

Notizen: The structure and configuration of gilmaniellin, a metabolite of Gilmaniella humicola BARRON, has been shown to be 2 by X-ray analysis. By comparison of spectral data structure 1 has been assigned to dechlorogilmaniellin.

Notizen: Cycloadditions of 3,4-dimethoxyfuran with benzoquinonesCycloaddition of 3,4-dimethoxyfuran (3,4-DF, 1) with 1,4-benzoquinones furnishes isolable (2 + 4)-adducts in high yield. The crystalline products with benzoquinone, 2-methyl-benzoquinone, 2,3-dimethoxy-benzoquinone have endo-configuration, whereas 2,3-dimethyl-benzoquinone gives the exo-adduct 4c exclusively. Halogens (Cl2, Br2) add rapidly across the highly nucleophilic double bond of 3 or 4 in stereospecific cis-manner, and exclusively from the exo-side. The product 5c shows no sign of enolization to the hydroquinone; but with 3a and 3d the hydroquinones 6 were found. Methanolysis of 5 leads to the stable acetals 7 and 8. On oxidation of the hydroquinones 7 the thermolabile quinones 10 were obtained. Preparative pyrolysis of 10a under relatively mild conditions (N2, 200°, 0.1 Torr) gives tetramethoxy ethene (11) and isobenzofuran-4,7-quinone 12, a yellowish, crystalline and stable compound.

Notizen: The acid-catalyzed hydrolysis of CF3CHN2 (1) follows an A2 mechanism of preequilibrium protonation and rate-determining solvolysis of the intermediate diazonium ion 4; this was demonstrated by: (a) the inverse kinetic isotope effect; (b) H-D exchange; (c) the unimportance of general acid catalysis; (d) strong rate acceleration by added nucleophiles. The activation parameters have been determined in two solvent systems. In contrast to 1 the secondary diazocompound CF3—CN2—CH3 (2) follows the normal A-SE2 mechanism of rate-determining proton transfer.

Notizen: Lithium- and copper-derivatives of α,α-doubly deprotonated nitroalkanes. Generation, properties and reactions with alkyl- and allylhalidesAus der Dissertation von F.L., ETH Zürich, 1979; Nr. 6356. Die Arbeiten wurden teilweise am Institut für Organische Chemie der Justus-Liebig-Universität Giessen durchgeführt. Vorläufige Mitteilungen siehe [1] und [2].Primary nitroalkanes are deprotonated twice in the α-position when treated with two mol-equiv. of butyllithium at -78° to -100° in THF containing HMPT to give dilithium derivatives 15 (the compound with R = C2H5 is stable up to -30°). The acidity of the nitronate proton of 13 is estimated to be in the same range as that of diisopropylamine. The C-nucleophilicity of the novel reagents 15 is dramatically increased as compared with that of simple nitronates 5: C,C-bond-forming reactions readily take place with alkylhalides (→22c-e,g,h,j-m) and benzylbromide (→22b,f,i); allylations are possible via nitroalkycopper-lithium-derivatives (→27-29).

Notizen: Electrochemical Investigations of the Enantiomer Selectivity of Chiral Ionophores in Liquid MembranesThe enantiomer selectivity of a series of chiral neutral ionophores was investigated by electrochemical methods using ionophore-solvent-polymer membranes and chiral ammonium salts as substrates. The potentiometrically determined enantiomer selectivities are in good agreement with the results of electrodialytic transport studies.

Notizen: Die vier diastereomeren Thioanalogen des (±)-MuscarinsIm Zusammenhang mit pharmakologischen Arbeiten über die chemische Natur des cholinergischen Rezeptors haben wir die reinen (±)-Thiomuscarinjodide 4a-d hergestellt und ihre relativen Konfigurationen an C(2), C(3) und C(5) an den nor-Basen 3a-d in 1H-NMR.-Spektren mit Lanthanidverschiebung aufgeklärt. Auf der Stufe der 3-Hydroxymide 2 wurden die vier Diastereomere chromatographisch voneinander getrennt.

Notizen: Monomolecular fragmentations of butadiyne- and 1,3-pentadiyne radical cations in their electronically excited states have been investigated by use of the photoelectron-photoion coincidence technique. Breakdown curves for the molecular and various fragment ions have been recorded over the ionization energy range of 9 to 17 eV. These breakdown curves reveal the extent of the competition between the radiative relaxation (ion fluorescence) and the non-radiative internal conversion followed by fragmentation for the decay of the first excited electronic states. Extensive hydrogen scrambling and/or ionic-carbon-skeleton isomerization takes place prior to fragmentation, as revealed by the breakdown curves obtained for the site specifically deuteriated 1,3-pentadiynes.

Notizen: On cycloaddition reactions with 3,4-dimethoxyfuranWe describe new cycloadditions of 3,4-dimethoxyfuran (3,4-DF, 1) with various dienophiles. In contrast to furan, the reaction of 3,4-DF with maleic anhydride gives exo- and endo-adducts at approximately the same rate. The thermodynamically more stable product is again the exo-product. Less active dienophiles lead also to mixtures of exo- and endo-adducts, except for citraconic anhydride (methylmaleic anhydride) which forms only the adduct with an endo-methyl group. Dimethylmaleic anhydride could not be reacted with 3,4-DF.All adducts with 3,4-DF contain a hidden 1,2-dicarbonyl group in the form of an endiolether. Its pronounced nucleophilic character allows a series of further additions. Noteworthy are the stereospecific cis-additions of halogens and the preparation of several acetals. Ozonolysis of the enolether in 4 allows the preparation of the hitherto unknown 2r, 3trans, 4trans, 5cis-tetrahydrofuran tetracarboxylic acid and derivatives thereof (5 and 6).

Notizen: Mass spectrometric study of a series of alkane-α,ω-diphthalimidesAlkane-α,ω-diphthalimides with three to seven aliphatic C-atoms were synthesized and their mass spectral behaviour investigated in detail with the aid of the deuteriated derivatives of hexane-1,6-diphthalimide. Besides the expected hydrogen rearrangements, an interesting skeletal rearrangement has been observed.

Notizen: Diterpenoid Leaf-Gland Pigments: 11 Coleons and Royleanones from Coleus carnosus HASSK.The above mentioned plant has been investigated for its leaf-gland pigments. The following diterpenoids have been isolated (listed according to their elution from Sephadex LH-20, SiO2 and polyamide; in parentheses the yield of each product in g/kg dried leafs): royleanone (1)/6,7-dehydroroyleanone (2) (0.004, as a mixture); 7α-acetyloxyroyleanone (3, 0.009); a novel dimeric diterpene of hitherto unknown structure (0.03); horminone (4, 0.08); 6β-hydroxyroyleanone (5, 0.04, new as a natural product); 7α-acetyloxy-6β-hydroxyroyleanone (6, 5.45); 6β, 7α-dihydroxyroyleanone (7, 1.20); 7α-acetyloxy-6β, 20-dihydroxyroyleanone (8, 0.046, a novel compound); coleon U (9, 1.32); coleon V (10, 13.84); carnosolone (6α, 11, 12-trihydroxy-6,20-epoxymethano-abieta-8, 11, 13-trien-7-one (11), 1.25, a novel compound).Therefore, this plant is one of the richest one in royleanones and coleons so far investigated by us (pure crystalline compounds 2,3%, estimated total amount 〉 3% of dry weight). Among the isolated compounds carnosolone (11) is of special interest being the first of a group of colourless diterpenoids from Coleus- and Plectranthus- species turning blue on TLC. Its oxydation product 12 is one of the rare 4-acyl-ortho-quinones having high reactivity and characteristic spectral properties.

Notizen: Search for the Presence in Egg Yolk, in Flowers of Caltha palustris and in Autumn Leaves of 3′-Epilutein ( =(3R,3′S,6′R)-β,ε-Carotene-3,3′-diol) and 3′,O-Didehydrolutein ( =(3R,6′R)-3-Hydroxy-β,ε-carotene-3′-one)3′.O-Didehydrolutein ( =(3R, 6′R)-3-hydroxy-β,ε-carotene-3′-one; 2) has been detected in egg yolk and in flowers of Caltha palustris. This is the first record for its occurrence in a plant. The compound shows a remarkable lability towards base; therefore, it may have been overlooked til now, because it is destroyed under the usual conditions of saponification of the carotenoid-esters. One of the many products formed from 2 with 1% KOH in methanol has been purified and identified as the diketone 3 ( =(3R)-3-hydroxy-4′, 12′-retro-β,β-carotene-3′,12′-dione). The identification of this transformation product from lutein might throw a new light on the metabolism of this important carotenoid in green plants.3′-Epilutein ( =(3R,3′S,6′R)-β,ε-carotene-3,3′-diol; 1) was not detected in egg yolk, but is present besides lutein in flowers of C. palustris, thus confirming an earlier report of the occurrence of an isomeric (possibly epimeric) lutein (‘calthaxanthin’) in that plant [21].We were not able to detect even traces of 1 or 2 in the carotenoid fraction from autumn leaves of Prunus avium (cherry), Parrotia persica, Acer montanum (maple) and yellow needles of Larix europaea (larch).α-Cryptoxanthin (4), a very rare carotenoid, was isolated in considerable quantity for the first time from flowers of C. palustris.

Notizen: About the Stereospecific α-Alkylation of β-HydroxyestersIt was found, that dianions derived from β-hydroxyesters with lithium diisopropylamide (LDA) at -50 to -20° were alkylated stereospecifically (Scheme 1). The stereospecificity was 95-98%, the threo-compound (threo-2, -3 and -4) being the main product. This was proved for threo-2 and -3 by preparing the β-lactones 7 and 8, respectively, which were pyrolyzed to trans-1, 4-hexadiene (9) and trans-1-phenyl-2-butene (10), respectively (Scheme 2). Moreover, the acid threo-6 from threo-3 was converted by dimethylformamide-dimethylacetal to cis-1-phenyl-2-butene (11) (s. footnote 6).The alkylation of α-monosubstituted β-hydroxyesters also turned out to be stereospecific. Reduction of 16 and 18 with actively fermenting yeast furnished (+)-17 and (+)-2. respectively (Scheme 4), which were each mixtures of the (2R, 3S)- and the (2S, 3S)-isomers. Alkylation of (+)-17 with allyl bromide yielded after chromatography (2S, 3S)-19 and of (+)-2 with methyl iodide (2R, 3S)-19, the oxidation of which finally gave (S)-(-)-20 and (R)-(+)-20, respectively.

Notizen: Stereospecific Synthesis of (+)-(3R, 4R)-4-Methyl-3-heptanol, the Enantiomer of a Pheromone of the Smaller European Elm Bark Beetle (Scolytus multistriatus)Reduction of 2 with actively fermenting baker's yeast gave (-)-3. Stereospecific alkylation [3] of (-)-3 with propyl iodide furnished ethyl (+)-(2R, 3R)-2-propyl-3-hydroxypentanoate ((+)-4, 58%) which was converted to the tetrahydropyranyl ether (-)-5, then the alcohol 6, the p-toluenesulfonate 7 and the thiophenyl ether 8 to give the title compound (+)-1. The latter consisted of 97% of the threo- and 3% of the erythro-isomer. The above synthesis also correlates the absolute configuration of (-)-(R)-3 with that of (+)-(R)-citronellic acid (see [2]).

Notizen: Activated Quinones: Regiospecific Syntheses of Substituted Dibenzo [b, d]pyran-6-ones and Benzo[b]naphtho [d]pyran-6-onesThe reaction of 2-methoxycarbonyl-1, 4-benzoquinone (1) with substituted phenols leads in an acid-catalyzed, regiospecific way to substituted dibenzo [b, d]-pyran-6-ones (compounds 3 and 6). The cycloaddition of 1,3-butadiene to the latter yields compounds 7. Tautomerisation of 7 and oxidation gives the benzo[b]-naphtho[d]pyran-6-ones 8 and 10, respectively.

Notizen: The synthesis and biological testing of analogues of Met-enkephalin, a recently discovered opioid peptide from mammalian brain, are described. Testing involved determination of affinity constants for an opiate receptor site and of analgesic potency in the tail-flick test in mouse. The effects on opioid activity of modifying various parts of the enkephalin molecule are discussed. Tyr-D-Ala-Gly-MePheMet (O)-olThe ending -ol added to the symbol of an amino acid designates the aminoalcohol obtained by reduction of the α-carboxyl group of the amino acid. (FK 33-824), which was highly active in these tests, was subsequently selected for clinical testing.The use of two complementary models - in vitro binding studies and in vivo test for analgesia - for the assessment of biological activity in the evaluation of analogues is explained.

Notizen: Total Synthesis of Natural α-Tocopherol. I. Preparation of Bifunctional Optically Active Precursors for the Synthesis of the Side Chain by Means of Microbiological TransformationsOur concept for a new total synthesis of natural α-tocopherol includes the synthesis of a corresponding (3 R, 7 R)-configurated C15 side chain to be built up by using twice an optically active C5 unit together with an achiral C5 end part. (S)-3-methyl-γ-butyrolactone (11) and (S)-2-methyl-γ-butyrolactone (9) represent suitable bifunctional C5-precursors for this purpose. These two key compounds have been prepared by fermentative transformation including the enantioselective hydrogenation of the double bond of ethyl-4, 4-dimethoxy-3-methylcrotonate (5) by bakers yeast (yielding 11 after ester hydrolysis and cyclization of the fermentation product) and (E)-3-(1′, 3′-dioxolan-2′-yl)-2-buten-1-ol (8) by the fungus Geotrichum candidum (yielding directly 9).

Notizen: Total Synthesis of Natural α-Tocopherol(-)-(S)-2-Methyl-γ-butyrolactone (2) represents a versatile chiral C5-synthon. It serves as key intermediate in one of the syntheses of certain isoprenoid derivatives such as (R)-dihydrocitronellol, (3R, 7R)-hexahydrofarnesol and vitamin E of natural configurations. Their syntheses are described in detail.

Notizen: Oligomers of leucine, methionine, phenylalanine, and tyrosine were prepared enzymatically (using papain) from the respective methyl esters, with yields ranging from 51-96%. The effect of pH, buffer and salt concentration, and addition of alcohol on the oligomerization of leucine methyl ester was examined. The limits and potentialities of the enzymatic reaction as a method for obtaining monodisperse oligomers are discussed.

Notizen: Reaction of N-benzyl-N, N-di-(p-nitrobenzene)sulfonamide (3) with NaCN/HMPA at 140° affords N-benzyl-p-nitroaniline (4). The same product is obtained upon heating of the sodium salt of N-benzyl-(p-nitrobenzene)sulfonamide (5). The transformation 5 → 4 is believed to proceed via an anionic episulfonyl compound 6.

Notizen: Synthesis of 4(5)-Acyl-5(4)-alkylimidazoles from Symmetrical 1,3-DionesA new synthesis of 4(5)-acyl-5(4)-alkylimidazoles 1 is described. The symmetrical 1,3-diones 5a and 5b were reacted with N2O4 to give the nitro compounds 7a and 7b, respectively; 5c was treated with NaNO2 to give the nitroso compound 7c (Scheme 2). Hydrogenation of 7a, 7b and 7c over Pd/C in acetic acid/acetic formic anhydride yielded the formamides 9a, 9b and 9c, whose cyclization in formamide/formic acid afforded the 4(5)-acyl-5(4)-alkylimidazoles 1a, 1b and 1c, respectively. Oxazoles 11a and 11b were obtained from the corresponding formamides 9a and 9b with methanesulfonic acid/P2O5.

Notizen: Syntheses of the alcohols 10 and 18, and the corresponding ketones 11 and 19 are presented. Endo-5, exo-6-bis (chloromethyl)-endo-3-chloro-exo-2-norbornanol (16) and endo-5-(bromomethyl)-exo-6-(chloromethyl)-endo-3-chloro-exo-2-norbornanol (17) were obtained by HCl- and, respectively, HBr-addition to endo-5, exo-6-bis (chloromethyl)-exo-2, 3-epoxynorbornane (5). The Wagner-Meerwein rearrangement was precluded in these reactions probably because of the formation of a relatively stable chloronium ion 15 arising from the participation of the 1,4-chlorine atom of the endo-5-chloromethyl group in the heterolytic ring opening of the epoxide 5.The ‘naked’ fluoride anion (excess CsF in DMF or KF in DMF with 18-crown-6-ether) permitted the selective elimination of 2 equivalents of HCl from 16 and yielded the chlorohydrin-diene 18.

Notizen: As a study preliminary to attempts at photoaffinity and cooperative affinity labelling of cells and cell membrane vesicles bearing opiate receptors, the title compounds were prepared and tested by rat brain membrane binding assays and by a modified guinea-pig ileum bio-assay. The potency of the two compounds in both systems was considerably greater than that of the standard peptide, [Leu5]enkephalin, justifying further work with these and similar compounds.

Notizen: Electrocyclic reactions connecting radical cations are compared with those of the parent neutrals. Principles governing over-all reactivity and stereoselectivity of the open-shell processes are discussed.

Notizen: The previously discussed principles involved in electrocyclic reactions of openshell ions are exemplified for a type C system, the radical cation couple quadricyclane+ (Q+)/norbornadiene+ (NBD+). Exhaustive calculations (MINDO/3) for the various states of the ions support the general predictions for such types of systems. The barrier of interconversion Q+ → NBD+ is estimated to be significantly lower than that for the corresponding neutrals. Experimental support to this prediction is obtained by γ-irradiation of Q or NBD in an electron scavenging matrix. In both cases only NBD+ is observed, indicating that Q+ is not stable at 77 K. Previous observations and propositions referring to the system Q+/NBD+ are discussed in view of the present findings.

Notizen: Thirteen peptides, analogues of bradykinin (BK), enkephalin, Substance P (SP) and [Sar1]-angiotensin II ([Sar1]-ATII) have been synthesized by the solid-phase method. In all these peptides the residue Phe and Tyr were substituted with the boron-containing amino-acid L-o-carboranylalanine (Car). The purity and identity of the peptides were established by TLC., cellulose-electrophoresis and amino acid analysis.

Notizen: The electronic properties of a variety of methylated isoalloxazine derivatives have been investigated with absorption and fluorescece techniques (Table 1). The spectral effects of methyl substitution at different positions in the isoalloxazine ring are interpreted in terms of different bond orders between the C-atoms of the methyl groups and of the aromatic ring. Methyl groups at C(6) or C(9) induce quenching of the fluorescence and shortening of the lifetime whereas a methyl group at C(7) has an opposite effect. The quenching effect might be due to strain in the molecular framework caused by the methyl groups.The lowest energy levels of the isoalloxazine cations are shifted to higher energy as compared to the neutral isoalloxazines. Apart from these shifts the trends in spectral behaviour upon methylation are similar to those observed for the neutral isoalloxazine (cf. Table 2). The fluorescence of the isoalloxazine cations is strongly quenched in auqeous solution and their lifetime much shortened. These observations indicated that there is substantial interaction between the charged fluorophore and the water dipoles and that this interaction produces efficient radiationless deactivation of the first excited singlet state.

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.