Chiroptical Data Research Articles

Crystal Structure and Chirality of the Ansamycin Antibiotic Actamycin

The structure of the title compound has been determined from diffractometer data recorded, initially, at 294 K and, subsequently, at 168 K. Crystals are triclinic, space group P1 with (168 K values in square brackets) a 16.080(2) [15.934(2)], b 15.958(2) [15.880(2)], c 8.443(2)Ǻ [8.233(1)Ǻ], α 85.55(1) [86.04(1)],β 82.65(1) [82.56(1)],γ 85.00(1)° [84.73(1)°], and contain two actamycin and two solvent ( tetrahydrofuran ) molecules in the asymmetric scattering unit. The structure was solved with DIRDIF and refined by block-diagonal least-squares analysis (of 168 K data) to R 0.049 ( wR 0.069) for 5640 reflections and 940 refined parameters. Molecules of actamycin (30-dechloro-2-demethyl-30-hydroxynaphthomycin A) exhibit the same relative stereochemistry (8S*,9S*,15S*,18S*,19S*,20S*) and double-bond configuration (2Z,4Z,6E,12E,16E,21E) as reported for crystalline 25-O-methylnaphthomycin A iminomethyl ether but are quite differently conformed. The two crystallographically inequivalent actamycin molecules in the present structure also exhibit substantial conformational (torsion angle) differences due, apparently, to the effects of intermolecular hydrogen bonding. Consideration of chiroptical data defines the absolute configuration of actamycin as 8S,9S,15S,18S,19S,20S and the helicity as P, as in naphthomycin A.

Synthesis and properties of some Rh(I) catalytic complexes with dinitrogen ligands derived from 5-Pyrido-1,4-benzodiazepin-4-ones

A series of bidentate nitrogen ligands ( 3–8), and their [Rh (I) (NBD) (N-N)] ClO 4 complexes 11–14 (NBD-norbornadiene, N-N-dinitrogen ligand) were prepared. Conformational properties and stability of 4 and its catalytic complex 12 were reported. Catalytic activity of complexes 11 and 12 in hydrogenation of cyclohexane is compared with 22, a complex that contains 2,2′-bipyridyl as the “standard” ligand. Chiroptical data of chiral ligands 5,6 and their Rh(I) complexes 13,14 are reported.

Carotinoide mit 7‐Oxabicyclo[2.2.1]heptyl‐Endgruppen. Teil I. Versuch einer Synthese von Cycloviolaxanthin (= (3S,5R,6R,3′S,5′R,6′R)‐3,6:3′,6′‐Diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐carotin‐5,5′‐diol)

Carotenoids with 7‐Oxabicyclo[2,2.1]heptyl End Groups. Attempted Synthesis of Cycloviolaxanthin ( = (3S,5R,6S,3′S,5′R,6′R)‐3,6:3′,6′‐ Diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐carotin‐5,5′‐diol)Starting from our recently described synthon (+)‐24, the enantiomerically pure 3,6:4,5:3′,6′:4′,5′‐tetraepoxy‐4,5,4′,5′‐tetrahydro‐ε,ε‐carotene (34) and its 15,15′‐didehydro analogue 32 were synthesized in eleven and nine steps, respectively (Scheme 4). Chiroptical data show, in contrast to the parent ε,ε‐carotene, a very weak interaction between the chiral centers at C(5), C(5′), C(6), C(6′), and the polyene system. Diisobutylaluminium hydride reduction of 32 lead rather than to the expected 15,15′‐didehydro analogue 35 of Cycloviolaxanthin (8), to the polyenyne 36 (Scheme 5). We explain this reaction by an oxirane rearrangement leading to a cyclopropyl ether followed by a fragmentation to an aldehyd on the one side and an enol ether on the other (Scheme 6). This complex rearrangement includes a shift of the whole polyenyne chain from C(6), C(6′) to C(5), C(5′) of the original molecule.

Synthese von enantiomerenreinen ‘Grasshopper’‐Ketonen und verwandten Verbindungen

Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related CompoundsStarting from our previously described synthon 1, the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4‐(2′,4′‐dihydroxy‐2′,6′,6′‐trimethylcyclohexylidene)but‐3‐en‐2‐ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.

Feroxidin, a novel 1-methyltetralin derivative isolated from cape aloe

The structure and the preferred conformation of feroxidin ( 1) are determined by spectroscopic methods ( 1HNMR, NOE, CD). The absolute configuration is deduced from chiroptical data. Feroxidin represents the first 1-methyltetralin occurring in plants.

Cu(I)-thionein release from copper-loaded yeast cells

The release of intact Cu(I)8-thionein from copper-resistant copper-loaded yeast cells, strain X2180-1Aa, has been shown. This copper(I)-thiolate-rich protein was characterized and compared with the chemical and physiocochemical properties of intracellular yeast Cu-thionein. The same molecular mass and stoichiometry of 8 mol copper atoms/mol protein was found. No detectable difference between the Cu-thioneins was seen in luminescence emission, electronic absorption in the ultraviolet region, chiroptical data or amino acid composition. The importance of stable Cu(I)-thiolates in Cu-thionein as a safe vehicle for transporting copper in a non-reactive manner is confirmed.

The influence of side-chains on the dilute-solution properties of three structurally related, bacterial anionic polysaccharides

Viscometric, calorimetric, and chiroptical data collected by using dilute aqueous solutions of the extracellular polysaccharides [Me 4N + salt form] from Pseudomonas elodea (S-60), Alcaligenes (ATCC 31555) (S-130), and Alcaligenes (ATCC 31961) (S-194) over a range of ionic strength (Me 4NCl concentrations) and temperature are reported. The data demonstrate that increasing the ionic strength of dilute solutions of the nonbranched S-60 at 25° promotes a distinctly co-operative, conformational transition over a narrow range of added salt concentration. Moreover, over the range of ionic strength examined, S-60 also undergoes a thermally reversible, conformational transition which exhibits no hysteresis: the temperatures at the midpoint of the sigmoidal transitions ( T M) increase moderately with increasing ionic strength. This conformational ordering has been monitored under conditions where S-60 does not gel. However, because both higher concentrations of S-60 at the same ionic strength, and higher ionic strengths at the same S-60 concentration, lead to gel formation, it is likely that the conformational ordering we have observed is the one involved in the gelation of S-60. The data also indicate that the two different modes of branching along the S-60 backbone present in S-130 (α- l-rhamnose and α- l-mannose linked to O-3 of the d-glucose after the d-glucuronic acid in the tetrasaccharide repeating-unit) and S-194 [β- d-glucopyranosyl-(1 → 6)-α- d-glucopyranosyl units linked to O-6 of the d-glucosyl residue before the d-glucosyluronic acid] mediate against conformational ordering. This is consistent with the fact that S-60 forms firm aqueous gels, whereas S-130 and S-194 are non-gel-forming, but give stable, highly viscous solutions. In addition, the measurements indicate that the carboxyl group in S-30 is in a screened, molecular environment. It is suggested that this screening could arise from hydrogen bonding involving the l-rhamnose- l-mannose side-chains.

Optisch aktive Lycopin‐epoxide und Lycopin‐glycole: Synthesen und chiroptische Eigenschaften

Optically Active Lycopene Epoxides and Lycopene Glycols: Synthesis and Chiroptical PropertiesWe present extensive spectral and chiroptical data on the pure and crystalline lycopene diepoxides 1–3 and glycols 4–9. A first synthetic approach to 1–9 with (+)‐malic acid as starting material afforded 30 as a complex mixture of isomers (Scheme 1). Pure stereoisomers 1–9 were obtained using the enantiomerically pure epoxygeraniol 31 as starting material (Scheme 2). Differentiation of the (5Z)‐from the (all‐E)‐isomers by 1H‐NMR and UV/VIS alone is very difficult.

Age dependence and charge isomers of bovine erythrocyte Cu 2Zn 2superoxide dismutase

An improved simple and efficient method for the aqueous isolation of bovine erythrocyte Cu 2Zn 2- superoxide dismutase was devised and successfully employed. In the last purification step the preparative separation of charge isomers of this enzyme was performed. The properties of the isomers were examined using electrophoresis, isoelectric focusing and chromatofocusing. The isoelectric points of charge isomers I and II were 5.2 and 4.9, respectively. No significant differences of chemical and spectrometrical properties, including amino acid composition, XPS-spectroscopy and EPR-measurements, were seen. The chiroptical data at 261 nm differed markedly. Aqueously isolated Cu 2Zn 2superoxide dismutase from the red blood cells of 1–2 year old cows had the same properties compared to the protein obtained from 12–15 year old species. For this reason, ageing of the erythrocyte was not attributed to an ageing of superoxide dismutase. Hydrogen peroxide was used as a model system for the generation of charge isomer II from charge isomer I. After treatment with hydrogen peroxide the band intensity at the position of charge isomer II increased dramatically, both during isoelectric focusing and/or gel electrophoresis. The data obtained from this species by CD-, EPR- and UV-spectroscopy are completely different from the respective parameters of the genuine charge isomer II. Therefore, it is concluded that this isomer is not generated by hydrogen peroxide inactivation of charge isomer I in vivo.

Enantiomers of Benzothiadiazine Diuretics by Direct Chromatographic Resolution of the Racemic Drugs

A number of racemic benzothiadiazine diuretics and two carbonyl analogue drugs were resolved into their optical isomers by liquid chromatography on chiral polyacrylamides 1. Enantiomeric resolution, which was, in some cases, almost complete, depended considerably on the substitution of the heterocyclic moiety of the drug molecules. Synthesis of the new adsorbent Ib is described. The enantiomers of the benzothiadiazines penflutizide (2a) and bendroflumethiazide (2b) in high optical purity, as well as enriched (+)-buthiazide (2j) were obtained by repeated chromatography on a semipreparative scale. Chiroptical data, optical purity employing the chromatographic method, and first-order racemization kinetics as a function of pH in aqueous solutions were determined.

Synthesis, chiroptical properties and absolute configuration of α-phenylglycidic acid

The (+)- and (-) enantiomers of potassium α-phenylglycidate, an irreversible inhibitor of the enzyme mandelate racemase, were synthesized by resolution of the diastereomeric esters with R-(-)-2-octanol. Base-catalyzed ring-opening of the resolved α-phenylglycidate esters gave the enantiomers of 2,3-dihydroxy-2-phenylpropanoic acid, also obtained by resolution of the racemic dihydroxy acid using ephedrine. A comparison of the chiroptical properties of the esters of α-phenylglycidic and 2,3-dihydroxy-2-phenylpropanoic acids with those of the structurally similar atrolactic and mandelic acids and their 2-methoxy-derivatives showed that the (-)-methyl 2,3-dihydroxy-2-phenylpropanoate corresponding to the (+)-enantiomer of potassium α-phenylglycidate, as well as the esters of α-phenylglycidic acid derived from the same (+)-potassium salt, were all configurationally related to S-(+)-atrolactic and mandelic acids. The configurational assignments made on the basis of the chiroptical data were confirmed by lithium aluminum hydride reduction of the (-)-2-octyl S- and R-α-phenylglycidates, which led exclusively to the R-(-)- and S-(+)-2-phenyl-1, 2-propanediols, respectively, previously related configurationally to R-(-)- and S-(+)-atrolactic acids.

ChemInform Abstract: NOVEL, RACEMIC OR NEARLY‐RACEMIC ANTIBACTERIAL BROMO‐ AND CHLOROQUINOLS AND Γ‐LACTAMS OF THE VERONGIAQUINOL AND THE CAVERNICOLIN TYPE FROM THE MARINE SPONGE APLYSINA (= VERONGIA) CAVERNICOLA

AbstractAus der Titelspezies werden die lndole (I) [quasi‐Bootkonformation für (Ia), (Ib) und (Ie) (e.e.

Novel, racemic or nearly‐racemic antibacterial bromo‐ and chloroquinols and γ‐lactams of the verongiaquinol and the cavernicolin type from the marine sponge Aplysina (= Verongia) cavernicola

AbstractButanolic extracts of the Mediterranean sponge Aplysina (= Verongia) cavernicola have given, by reverse‐phase HPLC, the antibacterial quinols (±)‐3‐bromoverongiaquinol (= (±)‐3‐bromo‐1‐hydroxy‐4‐oxo‐2,5‐cyclohexadine‐1‐acetamide; 1d) and (±)‐3‐bromo‐5‐chloroverongiaquinol (= (±)‐3‐bromo‐5‐chloro‐1‐hydroxy‐4‐oxo‐2,5‐cyclohexadine‐1‐acetamide; 1c) besides the products of their formal cyclization 5‐chlorohexadiene‐1‐acetamide; 1c) besides the products of their formal cyclization 5‐chlorocavernicolin (= 5‐cloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 6), the C(7)‐epimerizing 7β‐bromo‐5‐chlorocavernicolin (=7 β‐bromo‐5‐chloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 4a and 7α‐bromo‐5‐chlorocavernicolin (4b), and the C(7)‐epimerizing 5‐bromo‐7β‐chlorocavernicolin ( = 5‐bromo‐7β‐chloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 5a) and 5‐bromo‐7α‐chlorocavernicolin (5b). The latter four were isolated as mixtures of C(7)‐epimerizing monoacetates 4a′/4b′ and 5a′/5b′. Both 1 and 1c proved to be racemic from NMR examination of their esterification products with (–)‐methyl‐oxyacetic acid, whilst 6 had a ca. 6% enantiomeric purity as shown by a 1H‐NMR study of its monoacetate 6′ in the presence of a chiral shift reagent. These chiroptical data of the first chiral quinols from the Verongida and of 6 suggest phenol oxidative routes from tyrosine precursors for their formation. In view of their bioactivities, 1d and 1c have been synthesized from (p‐hydroxyphenyl)acetic acid byt phenol oxidative routes.

ChemInform Abstract: ABSOLUTE CONFIGURATION OF GILMANIELLIN

AbstractDie Titelverbindung (Ia) hat die gleiche absolute Konfiguration, wie ihr Dechloro‐Derivat (Ib), dessen absolute Konfiguration aus dem CD‐[Vorzeichen des (n ‐ nÜ‐Cotton‐Effekts] und dem UV‐Spektrum abgeleitet wird.

Absolute Configuration of Gilmaniellin

AbstractThe absolute configuration of dechlorogilmaniellin (2) could be determined from its chiroptical data by applying coupled‐oscillator theory to the CD couplet around 272 nm and from the sign of its n →π* Cotton effect. Gilmaniellin (1) has the same absolute configuration.

Sugar enolones, XIX. An approach to actinospectose‐type 2,3‐diketo sugars. – Synthetic proof for the R configuration of “Herzgift‐Methylreduktinsäure”︁

AbstractA stereochemically defined, preparatively satisfactory access is described to stable derivatives of D‐actinospectose, a 4,6‐dideoxy‐D‐glycero‐hexopyranos‐2,3‐diulose (3a ⇌ 3b) realized in spectinomycin (1) and a series of Calotropis cardenolides (2). Key steps are the conversions of the 6‐deoxy‐D‐hydroxyglucal ester 8 either into the hexulose tribenzoate 10 (47%) by chlorination and hydrolysis, or into the α‐ulosyl bromide 12 (76%) via NBS bromination in the presence of methanol. The suitability of 12, as well as of the actinospectosyl chloride 6, for β‐selective introduction of the actinospectosyl moiety is demonstrated by silver carbonate‐promoted glycosylation and subsequent β‐elimination (12 → 14, 15), resulting in annulation (6 → 16) when reacted with diols. – Reduction of the free carbonyl function of the dibenzoylactinospectose 13 with zinc tetrahydroborate is followed by 3‐O → 2‐O‐benzoyl migration and β‐elimination to afford the stable benzoate 5 of “Herzgift‐Methylreduktinsäure”. The rotational and chiroptical data of 5 furnish unequivocal synthetic proof for the D (or R) configuration of the methyl‐bearing C‐5′ in Calotropis cardenolides.

Spirocoleone: Synthese und Charakterisierung von vier diastereomeren Spiro (methylcyclopropan)‐Substrukturen; Revision der Konfiguration an C(12) und C(15) von Coleon P und Derivaten sowie von Coleon‐Z‐Derivaten; Röntgenstrukturanalysen von Lanugon J und weiteren Spirocoleonen

Spirocoleons: Synthesis and Characterization of Four Diastereomeric Spiro (methylcyclopropane) Substructures; Revision of the Configuration at C(12) and C(15) of Coleon P and Derivatives and Coleon‐Z Derivatives; X‐Ray Analysis of Lanugon J and of Further SpirocoleonsX‐ray analyses show the correctness of the previously published structure of coleon Q (1), establish the structure of lanugon J (4a), and necessitate a revision of the configuration at C(12) and C(15) in coleon P (3a) and its derivatives 3b and 3c, and furthermore of the coleon Z derivatives 11a–11d. Two further diastereomeric spiro (methylcyclopropane) substructures have been generated by photoisomerization of lanugon J (4a) and 12‐O‐desacetylcoleon N (8); they represent the novel cis‐type B with (12R, 13R, 15S)‐ and the novel trans‐type D with (12R, 13R, 15R)‐configuration (Scheme 1). The structures of the photoproducts 5a ((12R, 13R, 15R)‐lanugon J) and 7a ((12R, 13R, 15S)‐lanugon J) were established by X‐ray analysis. So far, only two of the eight possible diastereomers of the spiro‐(methylcyclopropane) substructure I have been detected in nature, i.e. the trans‐type A with (12R, 13S, 15S)‐ and the cis‐type C with (12R, 13S, 15R)‐configuration. The four diastereomers A‐D, all possessing (12R)‐configuration, show very similar properties. However, careful comparison of spectral and chiroptical data allow a differentiation, even in the case of functionalization of H3C(17). The (12S)‐counter‐parts could not yet be prepared.

Constitution and absolute stereochemistry of the antibiotic sarubicin A.

By spectral (UV-VIS, IR, NMR, MS and CD) methods the quinone antibiotics sarubicin A and U-58,431 were shown to have identical constitution and stereochemistry. Chiroptical data and their theoretical analysis have settled the common absolute configuration as 5S, 6R, 8R, 10R.

Calorimetric and chiroptical data on the interaction between ionic polysaccharides and complex ions in aqueous solution

Calorimetric and chiroptical data on the interaction between ionic polysaccharides and complex ions in aqueous solution

Carotenoids of shellfishes. Absolute configuration of pectenolone.

The absolute configurations of pectenolone [(3S, 3'R)-3, 3'-dihydroxy-7', 8'-didehydro-β, β-caroten-4-one] ex patinopecten yessoensis have been established from chiroptical data of pectenolone and its 2, 3-didehydro derivative.