Showing papers in "Helvetica Chimica Acta in 1983"

13C‐NMR.‐Spektroskopie von Organolithiumverbindungen bei tiefen Temperaturen. Strukturinformation aus der 13C, 6Li‐Kopplung

Abstract: Low-Temperature 13C-NMR. Spectroscopy of Organolithium Derivatives. - 13C, 6Li-Coupling, a Powerful Structural Information The 13C-NMR. spectra of thirteen lithiated hydrocarbons (1c–13c. Table 2) and of eighteen a-halo-lithium carbenoids (14c–31c, Table 3) have been recorded in donor solvent (R2O, R3N) mixtures at temperatures down to −150°. The organolithium species were generated from singly or doubly 13C-labelled precursors by H/6Li- or Br/6-exchange. - 13C, 6Li-Coupling was observed of all species but those which supposedly contain contact ion pair C,Li-bonds (benzylic and acetylenic derivatives). The multiplicities of the signals are correlated with the degree of aggregation in solution: the triplets of the halocarbenoids must arise from monomers or heteroatom-bridged oligomers, the quintuplets of butyl-, cyclopropyl-, bycyclo[1.1.0]butyl-, vinyl-, and phenyllithium from dimers with planar arrangement of two Li- and two C-atoms, as known from crystal structures (Scheme 3). All 13C, 6Li-couplings are temperature-dependent, dynamic processes cause them to disappear above ca. −70° (Fig. 1–4). - Types of organolithium compounds are categorized according to the change of chemical shift δΔ (H, Li) upon H/Li-substitution, according to the 13C, 6Li-coupling constants ranging from 0 to 17 Hz, and according to the multiplicities which indicate the aggregation: type A are Li-derivatives of alkanes and cycloalkanes, type B are s-bonded vinyl, aryl, and alinyl derivatives, type C are a-heterosubstituted (RS, hetero=halogen) organolithium compounds, and type D are π-bonded allylic and benzylic systems (Table 5). The C,Li-distances in the crystal structures of representatives of all four classes are within the small range of 2.18–2.28 A (cf. Scheme 3). - Some surprising observations and their interpretations and consequences are: (a) butyllithium solutions in THF, THF/TMEDA, and dimethyl ether contain increasing amounts of dimer upon cooling, the equilibrium (tetramer · 4 THF)+4 THF ⇌ 2 (dimer · 4 THF) being shifted to the right (Fig. 1 and Scheme 4); thus, more of a different species is present at low temperatures, with the accompanying changes in reactivity; (b) mixed higher aggregates are formed upon addition of butyllithium to bicyclobutyllithium; these are broken up to dimers upon addition of TMEDA (Tetramethylethylene-diamine) (Fig. 2 and Scheme 5); (c) the solid state, the calculated gas-phase and the solution species of phenyllithium all have dimeric structures, and so do vinyl and cyclopropyl lithium derivatives; the 13C-deshielding observed upon replacement of H by Li on sp2- and sp-C-atoms is related to a polarization of the π-electrons (Table 3, Fig. 3 and Scheme 6); (d) the spectra of halo-lithium carbenoids show three striking features as compared to the C,H-compound: deshielding of up to 280 ppm (Table 3), strong decrease of the coupling constant with 1H- and 13C-nuclei attached to the carbenoid C-atom (Table 4), and a structure-independant, almost constant, large 13C, 6Li-coupling constant of 17 Hz (Table 3); as shown in Scheme 7, these effects might be the consequence of a reduced degree of hybridization of the carbenoid C-atom. - The preparation of the labelled compounds and the generation of solutions of the organolithium compounds for NMR. measurements are described in full detail.

A Study of Stereoselective Hydrolysis of Symmetrical Diesters with Pig Liver Esterase

Abstract: Pig liver esterase-(PLE) catalyzed hydrolysis of dimethyl esters of symmetrical dicarboxylic acids, including meso-diacids, cis-1,2-cycloalkanedicarboxylic acids, and diacids with a prochiral center, was studied with 14 substrates. The products of these stereoselective hydrolyses are chiral monoesters of dicarboxylic acids, with an enantiomeric excess (e.e.) from 10% to 100%. Some of these optically active monoesters are valuable synthons in natural products synthesis. An additivity pattern of α- and β-substituents with the glutaric esters on the stereoselectivity of enzymatic hydrolysis was observed. Analysis of the experimental results leads to a model of enzyme stereoselectivity of diester hydrolysis in which the substitution pattern at α- and β-C-atoms is found to determine the absolute configuration of the resulting monoester.

On the stereochemistry of allylmetal-aldehyde condensations. Preliminary communication

Abstract: The stereochemical course of the intramolecular allylsilane-aldehyde condensation of 1a has been investigated. A modest preference for the product arising from a synclinal orientation of double bonds was observed with Lewis-acid catalysts. Cyclization induced by fluoride ion resulted in stereochemical reversal.

Efficient Molecular Catalysis of ATP‐Hydrolysis by Protonated Macrocyclic Polyamines

Abstract: Molecular catalysis of ATP-hydrolysis by a number of protonated macrocyclic polyamines 1–9 has been investigated by 31P-NMR spectroscopy, and marked rate enhancements have been obtained. The largest acceleration is produced by the [24]-N6O2 macrocycle 1, and the process displays the following properties: 1. protonated 1 forms very stable complexes with ATP, as well as with ADP and AMP; 2. it enhances the rate of ATP-hydrolysis by a factor of 103 at pH = 8.5; the rate of hydrolysis is constant over a wide pH-range, from pH = 2.5 to 8.5; 3. 1 is more efficient than acyclic analogues; 4. the products of the reaction are orthophosphate (OP) and ADP, which is subsequently hydrolyzed to OP and AMP at a slower rate; 5. at pH > 6.5, a transient species is detected, which is tentatively identified as a phosphoramidate intermediate, resulting from phosphorylation of the macrocycle 1; 6. the reaction presents first-order kinetics and is catalytic. The mechanism of the process is discussed in terms of initial formation of a complex between ATP and protonated 1, followed by an intracomplex reaction which may involve a combination of nucleophilic or acid catalysis with electrostatic catalysis.

Production of (+)‐(S)‐Ethyl 3‐Hydroxybutyrate and (‐)‐(R)‐Ethyl 3‐Hydroxybutyrate by Microbial Reduction of Ethyl Acetoacetate

Abstract: The production of (S)-ethyl 3-hydroxybutyrate (2) from ethyl acetoacetate (1) in higher yields and with higher optical purity than with the usual procedures was achieved by continuous addition of the substrate 1 and sucrose to an aerated suspension of bakers' yeast. The microbial reduction of 1 by the fungus Geotrichum candidumLINK yields - for the first time - the antipode 3.

Synthesis and Protonation Features of 24‐, 27‐ and 32‐membered Macrocyclic Polyamines

Abstract: Three macrocyclic polyamines [24]ane-N61, [32]ane-N82 and [27]ane-N6O33 of ring size 24, 32 and 27, respectively, have been synthesized. They contain either trimethylenediamine of ethylenediamine units. The acyclic analog 4, as the reference compound, was also prepared. Compounds 1–3 are macrocyclic analogs of natural polyamines and are potential ligands for metal cations as well as, when protonated, for anions. The protonation constants of compounds 1–4 have been determined. They are high enough for compounds 1–4 to be fully protonated in a pH-range close to neutrality, as required for binding of anions of weak acids. The effect of structural features on the protonation constants are briefly discussed in relation to the design of macrocyclic polyamine ligands.

Deoxy‐nitrosugars. 6th communication. Stereoelectronic control in the reductive denitration of tertiary nitro ethers. A synthesis of ‘C‐glycosides’

Abstract: The separate, radical denitration with Bu3SnH of the pyranose derivatives 3, 4, 9, and 10 gave in good yields exclusively the ‘C-glycosides’ 5 and 11, respectively (Scheme 1). Similar reduction of the cyclohexyl derivatives 15, 16, 19 and 20 gave 4:1 mixtures of 17, 18, 21 and 22, respectively, always with predominant formation of an axial C,H-bond. In the furanose series a divergent behaviour was observed for the D-mannose-derived nitro ethers 25 and 27 and the D-ribose-derived nitro ethers 30 and 31, respectively, in that the former two gave isomerically homogeneous reduction products (26 and 28, respectively; Scheme 3) and the latter a 1:1 mixture of the diastereoisomers 32 and 33(Scheme 4). The stereochemical results were explained on the basis of the stereoelectronic effect of the ring O-atom, the preferred conformation of the intermediate, pyramidal alkoxyalkyl radicals and steric effects in the trioxabicyclo [3.3.0]octane ring system.

Silicon-Directed Nazarov Reactions II. Preparation and Cyclization of β-Silyl-substituted Divinyl Ketones

Abstract: Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction.

The Preparation of Optically Pure 7-Oxabicyclo[2.2.1]Hept-2-Ene Derivatives - the Cd Spectrum of (+)-(1r)-7-Oxabicyclo[2.2.1]Hept-5-En-2-One

Abstract: Note: Univ lausanne,inst chim organ,ch-1005 lausanne,switzerland. Reference LGSA-ARTICLE-1983-011doi:10.1002/hlca.19830660627 Record created on 2005-11-09, modified on 2017-05-12

An enantioselective β-lactam synthesis starting from L-(S)-glyceraldehyde acetonide

Abstract: Complete diastereoselectivity is observed during the cyclocondensation of activated glycine derivatives with aldimines derived from L-(S)-glyceraldehyde acetonide. 3,4-cis-β-lactams are isolated in high optical and chemical yields. They are converted into key intermediates used in the syntheses of various mono- and bicyclic β-lactam antibiotics. A mechanism is suggested to explain this remarkable diastereoselectivity.

15N-NMR Spectra of Azoles with Two Heteroatoms

Abstract: The 15 N-NMR spectra of azoles, with natural isotope abundance, have been measured under different experimental conditions, and chemical shifts are reported for imidazoles, pyrazoles, oxazoles, isoxazoles, thiazoles, and isothiazoles. General trends of substituent effects in this heterocyclic series are discussed based on the data of 67 substituted azoles, dihydro- and tetrahydroazoles. 15 N, 1 H spin-coupling constants have been determined from spectra obtained by [ 1 H] → 15 N polarizationtransfer experiments, i.e. an application of INEPT and DEPT pulse sequences. Two-bond and three-bond coupling constants are fully assigned and are discussed in terms of the specific pathways in azoles. The potential of structural applications of the new data is illustrated for isomeric nitro-imidazoles and highly-substituted pyrazoles, and in the case of ring-chain tautomerism of 2-substituted tetrahydrooxazoles.

Synthesis of Cyclosporine. I. Synthesis of enantiomerically pure (2S,3R,4R,6E)‐3‐hydroxy ‐4‐methyl‐2‐methylamino‐6‐octenoic acid starting from tartaric acid

Abstract: Starting from R,R-(+)-tartaric acid, the synthesis of (2S,3R,4R6E)-3-hydroxy -4-methyl-2-methylamino-6-octenoic acid in 24 steps is reported. This novel amino acid is found in the cyclic undecapeptide cyclosporin A, isolated from the fungal strain Tolypocladium inflatumGAMS. Its stereospecific synthesis allowed, for the first time, the isolation and characterization of the new amino acid previously reported as the ‘C-9-amino acid’ [1].

Structural and Configurational Dependence of the Sensory Process in Steroids

Abstract: Structural modifications of testosterone and 19-nortestosterone have led to the synthesis of over 60 androstane and estrane derivatives whose sensory evaluation has allowed molecular parameters to be established for release of a ‘steroid-type’ scent. Odor perception with O-containing compounds in both classes has been found to be regioselective1. Osmophoric groups at C(3) were found to be the most active and specific. Functionality at C(2) is accompanied to a large extent by anosmic defects, and O-containing substituents at C(1) and C(4) appear to affect the receptor membrane in exceptional cases. A further characteristic of the ‘steroid-type’ scent is diastereoselectivity. The odor intensity of axial 2- and 3-hydroxysteroids is far greater than that of the equatorial epimers, and epimeric hydroxy-groups in the 1-, 4-, and 5-positions lead to almost complete absence of odor. In addition, only steroids with ‘normal’ ring junctions and configuration were found to be odorants, whereas compounds with cis-junctions between rings A and B, or C and D, were found to be practically inactive, Steroids therefore folow the ‘triaxial rule of odor sensation’. The most remarkable feature of our findings with steroid odorants is enantioselectivity1 . Whereas with C 19 -steroids of the ‘natural’ enantiomeric series the perception threshold is extremely low (<6 ppb), the corresponding ‘unnatural’ enantiomers have been found essentially odorless by a panel of 30 persons. This appears to be the first reported instance of a total enantioselective response to an odorant.

Photochemisch induzierte Reaktionen von 3-Amino-2H-azirinen

Abstract: Photochemically Induced Reactions of 3-Amino-2H-azirines Irradiation of 3-(N-methylanilino)-2H-azirines with a mercury low pressure lamp induces the cleavage of the C(2), C(3)-ring bond thus affording nitrilio-methanide dipols, substituted by an amino group at C(1). Depending on the substitution pattern at C(3), these intermediates can be trapped by dipolarophiles to yield five-membered heterocycles with high regioselectivity, or they undergo a 1,4-H-shift forming 2-azabutadiene derivatives. Further, the dipol is protonated at C(1) even by weak CH–acids.

Biosynthesis of Benzo[c]phenanthridine Alkaloids Sanguinarine, Chelirubine and Macarpine

Abstract: The biosynthesis of the benzo[c]phenanthridine alkaloids was investigated in a cell suspension culture of Macleaya cordata (papaveraceae). Feeding experiments define the biosynthetic pathway (–)-7,8,13,13a-tetrahydrocoptisine (–)-cis-N-methyl-7,8,13,13a-tetrahydrocoptisinium salt 15 protopine (5) sanguinarine (1) chelirubine (3) macarpine (4).

Singlet Oxygen and Superoxide: Experimental Differentiation and Analysis

Abstract: Reference LPI-ARTICLE-1983-007doi:10.1002/hlca.19830660236View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Optisch aktive C5‐Bausteine zur Synthese von natürlich vorkommenden Terpenen

Abstract: Optically Active C5-Synthons for the Synthesis of Naturally Occurring Terpenes The optically active synthons (S)-22, (R)-23, (R)-25 and (R)-26 were prepared from L-serine. Furthermore the tertiary alcohol 6 was synthesized from L-serine ((S)-6) and D-mannitol ((R)-6). These compounds are suitable for the synthesis of optically active natural products.

New Sesquiterpenoids from Clary Sage Oil (Salvia sclarea L.)

Abstract: Six sesquiterpenoids, (R, 5E)-2, 12-epoxycaryophyll-5-ene (1), (2 R, 5E)-caryophyll-5-en-12-al (2), (2S, 5E)-caryophyll-5-en-12-al (3), isospathulenol (4), (1R, 5R)- 1,5-epoxysalvial-4(14)-ene (5), and salvial-4(14)-en-l-one (6) have been identified for the first time in clary sage oil (Salvia sclarea L.). The structures and absolute configurations of 1–6 are corroborated by partial syntheses and their organoleptic properties are discussed. The compounds 5, 6 and mintsulfide (14) possess the rare C-skeleton C, for which the semisystematic name ‘salvialane’ is proposed. The sesquiterpenoids 1–5 are new.

Synthesis of Cyclosporine. Part II. Synthesis of Boc‐D‐Ala‐MeLeu‐MeLeu‐MeVal‐OH, a part of the peptide sequence of cyclosporine, by different strategic ways and synthesis of its isomers Boc‐D‐Ala‐MeLeu‐D‐MeLeu‐MeVal‐OH, Boc‐D‐MeLeu‐DMeVal‐OH, and Boc‐D‐Ala‐MeLeu‐MeLeu‐D‐MeVal‐OH as reference compounds

Abstract: Boc-D-Ala-MeLeu-MeLeu-MeVal-OH (DLLL) and its isomers DLDL, DLDD and DLLD were synthesized using several different strategic approaches and a modification of the mixed pivalic anhydride method for carboxyl activation. Alternatively, the tert-butoxy-carbonyl (Boc) or benzyloxycarbonyl (Z) amino-protecting groups and the benzyloxy (OBzl) or tert-butoxy (OtBu) carboxyl-protecting groups were used to protect the reacting peptides. By monitoring the reaction temperature, it was possible to synthesize, starting from the tripeptide DLL as peptide model, either the tetrapeptide DLLL (−20°) or the tetrapeptide DLDL (+20°), selectively. Using 1H-NMR spectroscopy to follow the mixed pivalic anhydride formation of the DLL- and DLD-tripeptides, it could be shown that anhydride formation is strongly dependent on the temperature. It is slow at −20° (several hours) and fast at +20° (20 to 40min). The isomerization of the DLL-anhydride to the more stable DLD-anhydride can be reduced to a minimum by working at −20°, while this isomerization proceeds to near completion at +20°.

Complexes macrocycliques des lanthanides: Stabilité et comportement électrochimique dans le méthanol et le carbonate de propylène

Abstract: Macrocyclic Complexes of Lanthanides: Stability and Electrochemical Behaviour in Methanol and Propylene Carbonate The stabilities of the 1:1 complexes of the trivalent lanthanides with the diazapolyoxamacrocycles (2.1.) and (2.2.1.) in anhydrous methanol and propylene carbonate have been determined at 25°, by competitive potentiometric methods using H+ or Ag+ as auxiliary cations, with Et4NClO4 as supporting-electrolyte. Additional data are also reported for the crown ethers 15C5 and 18C6 in propylene carbonate. It is shown that the diazapolyoxamacrocycles are much stronger complexing agents for trivalent lanthanides than macrocyclic polyethers, and that the bicyclic (2.2.1.) cryptates are more stable than the monocyclic (2.1.) complexes. With increasing atomic number of the lanthanides, the stability increases with diazapolyoxamacrocycles and decreases with cyclic polyethers. The electrochemical reduction of the trivalent samarium and europium cryptates has been investigated by polarography on a dropping Hg-electrode, in water and methanol. In both solvating solvents, the +2 oxidation states of the cations are stabilized by complexation.

The Carbon Zip Reaction: A Method for Expanding Carbocycles

Abstract: A general method for enlargement of carbocyclic rings by the so called zip reaction is given. The Michael adducts of 2-nitrocycloalkanones with 3-oxo-4-pentenoates in the presence of tetrabutylammonium fluoride give in high yield compounds with the ring enlarged by four C-atoms. By this method 7-, 8-, and 12-membered cycloalkanones were converted respectively to 11-, 12-, and 16-membered functionalized carbocycles (see Scheme 2 and 3).

Silicon-Directed Nazarov Reactions III. Stereochemical and Mechanistic Considerations

Abstract: The influence of remote substituents on the stereochemical outcome of electrocyclization in the silicon-directed Nazarov reaction has been examined. While the degree of stereocontrol was modest (ca. 3:1) the substituent in the major isomer (4,5 or 7-substituted cis-hexahydroind-2-en-1-ones) is always cis to the protons on the ring fusion. Thorough spectroscopic and conformational analysis revealed that divergent senses of electrocyclization are responsible for the observed products. Additional experiments suggest that steric, rather than stereoelectronic forces control the sense of cyclization. A qualitative description of the nature of reactive intermediates in the silicon-directed Nazarov reaction is proposed as well as an explanation for the remarkable efficacy of FeCl3 for inducing the reaction.

Total Synthesis of Neplanocin A

Abstract: The first total synthesis of racemic neplanocin A (1)1 from cyclopentadiene and acylnitroso-3,5-dinitrobenzoic acid is described. The synthesis is suitable for specific isotopic labelling of the hydroxymethyl group of neplanocin A.

Orthocarbonsäure-ester mit 2,4,10-Trioxaadamantanstruktur als Carboxylschutzgruppe; Verwendung zur Synthese von substituierten Carbonsäuren mit Hilfe von Grignard-Reagenzien

Abstract: Ortho Esters with 2,4,10-Trioxaadamantane Structure as Carboxyl Protecting Group; Applications in the Synthesis of Substituted Carboxylic Acids by Means of Grignard Reagents The surprising stability of 2,4,10-trioxa-3-adamantyl derivatives 1 against nucleophilic substitution by organomagnesium compounds is discussed and shown to be caused by unfavourable stereoelectronic and steric factors governing the substitution of these cage compounds (Scheme 2). As a consequence, a number of Grignard reagents 2 containing the carboxyl group masked as 2,4,10-trioxa-3-adamantyl group could be prepared and have been reacted in a second step with various electrophiles (cf. Scheme 4). In the products 7–13 and 15b the carboxyl masking group is removed by mild acid hydrolysis and saponification (cf. Scheme 3) to yield the corresponding acids 16a–21a, 22, and 23a. Acids 21a and 23a have been further transformed to give the macrocyclic lactones 24 and 26, isolated from Galbanum oleo-gum-resin, and acid 22 to give 12-methyl-13-tridecanolide (25), isolated from Angelica root oil. In addition 1-bromo-ω-(2,4, 10-trioxa-3-adamantyl)alkanes 1c and 1b have been used to synthesize (±)-methyl recifeiolate (29b) and pure cis-ambrettolic acid ((Z)-32a).

Synthesis of D‐ and L‐5‐Oxaproline and of a New Captopril Analogue

Abstract: The 1,3-dipolar cycloaddition of the C-t-butyloxycarbonyl-N-mannosyl-nitrone 5, formed in situ from the partially protected D-mannose-oxime 3 and the glyoxylate 4, to ethylene gave preferentially the (3S)-N-glycosyl-isoxazolidine 6 which was transformed into the 3-isoxazolidine-carboxylate (L-5-oxaproline ester) 12 and into some derivatives thereof. The (S)-configuration of 12 was proved by chemical correlation with a derivative of L-asparagine. The D-5-oxaproline ester was obtained from the corresponding N-ribosyl-nitrone 24. Two protected dipeptides containing either C-terminal- (28) or N-terminal-5-oxaproline (= Opro) (30) were synthesized. Starting from 12, the analogue 1 of captopril® (2) was prepared and its activity as an inhibitor of the angiotensin-converting-enzyme (ACE) was examined.

Photodecomposition of Liquid Water with TiO2‐Supported Noble Metal Clusters

Abstract: Rh- and Ru-loaded TiO2-particles were produced from cluster precursors (Rh6(CO)16, Ru3(CO)12) and their activity in mediating H2O-decomposition through band-gap excitation was investigated. Activity increases in the order Ru

Syntheses of Optically Active Verrucarinic Acid. 40th Communication on Verrucarins and Roridins

Abstract: Three syntheses of (2S, 3R)-2,5-dihydroxy-3-methylpentanoic acid (verrucarinic acid) and its derivatives suitably protected for the further transformation to macrocyclic trichothecenes are described. These involve an enantioselective ester hydrolysis by pig liver esterase, a Sharpless epoxidation and an asymmetric hydroboration.

Die Synthese von 2,3,4,5‐1H‐Tetrahydroimidazo[2,1‐b]chinazolin‐2,5‐dionen und analogen 2,3,4,5‐1H‐Tetrahydroimidazo[1,2‐a]thieno[2,3‐d] (bzw. [3,2‐d])‐pyrimidin‐2,5‐dionen

Abstract: The Synthesis of 2,3,4,5-1H-Tetrahydroimidazo[2,1-b]quinazolin-2,5-diones and analogous 2,3,4,5-1H-Tetrahydroimidazo[1,2-a]thieno[2,3-d] (or [3,2-d])-pyrimidin-2,5-diones The syntheses of various imidazo [2, 1-b]quinazolinediones and their thiophene analogs are described.

Das Carotinoidspektrum der Hagebutten von Rosa pomifera: Nachweis von (5Z)‐Neurosporin; Synthese von (3R, 15Z)‐Rubixanthin

Abstract: Carotenoids from Hips of Rosa pomifera: Discovery of (5Z)-Neurosporene; Synthesis of (3R, 15Z)-Rubixanthin Extensive chromatographic separations of the mixture of carotenoids from ripe hips of R. pomifera have led to the identification of 43 individual compounds, namely (Scheme 2): (15 Z)-phytoene (1), (15 Z)-phytofluene (2), all-(E)-phytofluene (2a), ξ-carotene (3), two mono-(Z)-ξ-carotenes (3a and 3b), (6 R)-ϵ, ψ-carotene (4), a mono-(Z)-ϵ, ψ-carotene (4a), β, ψ-carotene (5), a mono-(Z)-β, ψ-carotene (5a), neurosporene (6), (5 Z)-neurosporene (6a), a mono-(Z)-neurosporene (6b), lycopene (7), five (Z)-lycopenes (7a–7e), β, β-carotene (8), two mono-(Z)-β, β-carotenes (probably (9 Z)-β, β-carotene (8a) and (13 Z)-β, β-carotene (8b)), β-cryptoxanthin (9), three (Z)-β-cryptoxanthins (9a–9c), rubixanthin (10), (5′ Z)-rubixanthin (=gazaniaxanthin; 10a), (9′ Z)-rubixanthin (10b), (13′ Z)- and (13 Z)-rubixanthin (10c and 10d, resp.), (5′ Z, 13′ Z)- or (5′ Z, 13 Z)-rubixanthin (10e), lutein (11), zeaxanthin (12), (13 Z)-zeaxanthin (12b), a mono-(Z)-zeaxanthin (probably (9 Z)-zeaxanthin (12a)), (8 R)-mutatoxanthin (13), (8 S)-mutatoxanthin (14), neoxanthin (15), (8′ R)-neochrome (16), (8′ S)-neochrome (17), a tetrahydroxycarotenoid (18?), a tetrahydroxy-epoxy-carotenoid (19?), and a trihydroxycarotenoid of unknown structure. Rubixanthin (10) and (5′ Z)-rubixanthin (10a) can easily be distinguished by HPLC. separation and CD. spectra at low temperature. The synthesis of (3 R, 15 Z)-rubixanthin (29) is described. The isolation of (5 Z)-neurosporene (6a) supports the hypothesis that the ϵ-end group arises by enzymatic cyclization of precursors having a (5 Z)- or (5′ Z)-configuration.

Synthese von Glycerylätherphosphatiden 2. Mitteilung Herstellung von 2‐O‐Acetyl‐1‐O‐[(Z)‐9‐octadecenyl] ‐sn‐glyceryl‐3‐phosphorylcholin («Oleyl‐PAF»), des Enantiomeren sowie einiger analoger, ungesättigter Verbindungen

Abstract: Synthesis of Glyceryletherphosphatides, 2nd Communication. Preparation of 2-O-Acetyl-1-O-[(Z)-9-octadecenyl]-sn -glyceryl-3-phosphorylcholin (‘Oleyl-PAF’), of its Enantiomer and Some Analogous, Unsaturated Compounds Syntheses of the unsaturated glyceroletherphospholipid 1a as an olefin-analog of ‘Platelet Activating Factor’ (PAF) are described together with the methods for the preparation of the enantiomer 1′a, the corresponding ‘lyso compounds’ 1b and 1′b and their positional isomers 21a, 21′a, 26, 26′, 25, 25′ obtained on formally exchanging the attachment site of the functional groups at the glycerol moiety. Structural assignments and optical purity of the compounds are confirmed.