EFFICIENT RESOLUTION OF (±)-1-(9-ANTHRYL)ETHYLAMINE

ABSTRACT

Conditions for efficient resolution of (±)-1-(9-anthryl)ethylamine ((±)-1) by fractional crystallization of its salts with (S)-(+)-mandelic acid (2) are reported. When crystallization was performed by fast addition of chloroform solution of an equivalent of (±)-1 to the hot chloroform solution of (+)-2, crystals of mandelate of (+)-1-(9-anthryl)ethylamine ((R,S)-3) are collected in 56% yield. (R)-(+)-1 (98.6% e.e.) is isolated by extraction from bicarbonate solution of mandelate salt. Ulterior collection of four crops afforded (R,S)-3 with 71.5% cumulative yield and >98% e.e. of (+)-1 in a any single crop. With only 0.5 equivalents of (+)-2 crystallization afforded (R,S)-3 in 47.4% yield and (+)-1 with 98.1% e.e.     

Stereochemie von Metallocenen, 33. Mitt.: Optisch aktive Aryl-ferrocene, 4. Mitt.: Optisch aktive Ferroceno[b]indene,-hydrindene und verwandte Verbindungen

Zusammenfassung Optisch aktives Ferroceno[b]indenon (2) wurde durch kinetische Racematspaltung des gut zugänglichenendo-Ferroceno-indenols3 mit (+)--Phenylbuttersäure-anhydrid in optischen Ausbeuten um 20% erhalten. Aus den Ergebnissen dieser Racematspaltung (auch für dasexo-Carbinol5) ließen sich auf Grund der bekannten Absolutkonfiguration (+)-(1R)-2 die relativen stereochemischen Größen von Ferrocen und Benzol (Fc>Phenyl) erstmals festlegen.Mehrere Folgeprodukte von (+)-2 (darunter Ferrocenohydrindene) wurden dargestellt und ihre chiroptischen Eigenschaften mit jenen von strukturell verwandten Ferrocenderivaten (wie13–18) verglichen (und diskutiert). DieCD-Kurven wurden einer Bandenanalyse unterworfen.

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Stereochemistry of metallocenes, XXXIII. (ferrocenes, LIV). Optically active arylferrocenes, IV: Optically active ferroceno[b]indenes, hydrindenes, and related compounds

Optically active ferroceno[b]indenon (2) was obtained by kinetic resolution of the easily accessibleendo ferroceno indenol (3) with (+)--phenylbutyric anhydride with optical yields of 20%. From the results of this resolution (also for theexo-carbinol5) on the basis of the known absolute configuration (+)-(1R)-2 the relative stereochemical sizes of ferrocene and benzene could be established for the first time:Fc>phenyl.Several subsequent products of (+)-2 (amongst them ferroceno hydrindenes) were prepared and their chiroptical properties compared with those of structurally related ferrocenes (such as13–18) (and discussed). TheCD-curves were subjected to a band analysis.

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Mit 6 Abbildungen

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Herrn Prof. Dr.M. Pailer in herzlicher Verbundenheit zum 60. Geburtstag gewidmet.

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32. Mitt. (3. Mitt. über optisch aktive Aryl-ferrocene, 53. Mitt. über Ferrocenderivate):H. Falk, H. Lehner undK. Schlögl, Mh. Chem.101, 967 (1970).     

Prototropic acetylene-allene isomerization in planarly chiral ferrocenes. Intramolecular acymmetric induction in the course of the formation of chiral axis

Racemic 2-trimethylsilyl- and 2-trimethylstannyl-1-(3-phenyl-2-propynyl)ferrocene (rac-1a,b) as well as the dextrorotatory specimen of the latter, (+)-1b, were synthesized in two steps from racemic 1-formyl-2-trimethylsilyl- and 1-formyl-2-trimethylstannylferrocenes (2a,b) or from the levorotatory specimen of the latter, (–)-2b, respectively. On the contact with strongly alkaline alumina compounds1a,b and (+)-1b undergo diastereoselective prototropic acetylene-allene rearrangement to give predominantly one of the two possible stereoisomers of 2-trimethylsilyl- or 2-trimethylstannyl-1-(3-phenyl-1,2-propadienyl)ferrocenes,rac-4a,b or (+)-4b, depending on the starting material (d. e. 30–40 %). The extent of intramolecular asymmetric induction in the formation of the axially chiral fragment during the transformation of (+)-1b to (+)-4b is estimated at 38 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1111– 1115, June, 1994.The work was carried out with financial support from the Russian Fundamental for Basic Research (Project No.93-03-5827).     

Preparation of 4- and 6-desphenyl analogues of (−)-clausenamide and alternative synthesis of (+)-epi-clausenamide

4- and 6-desphenyl analogues of(-)-clausenamide,6 and 7,were prepared in optical active form from commercially available D-pyroglutamic acid and the known racemic pyrrolidinone 13,respectively.In order to confirm the absolute stereochemistry of(+)-and (-)-7,intermediate 19b was transferred into the(+)-epi-clausenamide 8.     

The absolute chirality of (+)-12-Bromo-[2.2]metacyclophane-4-carbonitrile

The absolute configuration of (+)-12-bromo-[2.2]metacyclophane-4-carbonitril [(+)-4 e] was determined by theBijvoet X-ray diffraction method as(R) _p (Fig. 1). This result allows the unambigous assignment of the absolute chiralities of all optically active 4-monosubstituted, 4,14-homodisubstituted, 4,12- and 4,14-heterodisubstituted [2.2]metacyclophanes chemically correlated with (+)-4 e. The result is compared with those obtained by other methods for establishing the absolute configuration.Stereochemistry of Planar Chiral Compounds, Part 8. Part 7:Krieger, Ch., Lehner, H., Schlögl, K., Mh. Chem.107, 195 (1976).     

Stereochemie von Metallocenen, 31. Mitt.: Optisch aktive Aryl-ferrocene, 2. Mitt.: Darstellung,absolute Konfiguration,Konformation und Circulardichroismus von α-substituierten Phenyl-ferrocenen

Zusammenfassung Ausgehend von optisch aktiver Phenylferrocen--carbonsäure (4 a), die man durch Oxidation von -Acetyl-phenylferrocen und Racematspaltung erhielt, wurden mehrere aktive Phenylferrocen-derivate dargestellt. Ihre absolute Konfiguration [(+)-(1R)-4a] und optische Reinheit ergab sich aus der chemischen Korrelation mit (+)-(1S)-Methylferrocen--carbonsäure (17) über (+)-2-Methyl-phenylferrocen, das aus (+)-4a durch Reduktion und aus (+)-17 durch Umwandlung in (+)-2-Methyl-aminoferrocen und Diazotierung in Benzol erhalten wurde. Ein optischer Vergleich von Methyl- mit Phenylferrocen-derivaten führte unter Berücksichtigung bevorzugter Konformationen zur selben Konfigurationszuordnung. DieCD-Kurven der Phenyl- und Methylferrocen-derivate wurden mit Hilfe eines Kurvenanpassungs-Rechenverfahrens einer Banden-analyse unterworfen, deren Ergebnisse diskutiert werden.

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Stereochemistry of metallocenes, XXXI. (Ferrocenes, LII). Optically active arylferrocenes, II: Syntheses, absolute configurations, conformations and circular dichroism of -substituted phenylferrocenes

Starting from optically active phenylferrocene--carboxylic acid (4a) which was obtained by oxidation of -acetyl phenylferrocene and optical resolution, several active phenylferrocene derivatives were prepared. Their absolute configurations [(+)-(1R)-4a] and optical purity followed from the chemical correlation with (+)-(1S)-methylferrocene--carboxylic acid (17)via (+)-2-methyl phenylferrocene, which was obtained from (+)-4a by reduction and from (+)-17 by conversion into (+)-2-methyl aminoferrocene and diazotation of the latter in benzene. An optical comparison of methyl-with phenylferrocene derivatives-considering the preferred conformations-led to the same configurational assignment. TheCD-curves of the phenyl- and methylferrocene derivatives were subjected to a band analysis with the aid of a curve fit-computerprogram, the results of which are discussed.

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52. Mitt. über Ferrocenderivate

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Mit 1 Abbildung     

Stereochemistry of planarchiral compounds,part XII: Absolute chiralities and X-ray crystal structures of 2,2′-Bi(1,6-methano[10]annulenyl)s

Summary The absolute chirality of the dextrorotatory main rotamer of 10,10-dibromo-2,2-bi(1,6-methano[10]annulenyl) (1 b), obtained by low temperature chromatography or by crystallisation of the (+)-enantiomer of1 b, was established by observation of anomalous X-ray diffraction as (+)-(R) _p (R) _a (R) _p -1b. This result was confirmed by reduction of (+)-1 b to a dextrorotatory 2,2-bi(1,6-methano[10]annulenyl) (1 a), which in turn was accessible by coupling of (–)-2-Bromo-1,6-methano[10]annulene (3) of known chirality (S) _p and, moreover, by enantioselective chromatography of1 a on triacetyl cellulose in ethanol. This correlation determines also the chirality of (+)-1 a as (S) _p (S) _p .According to the X-ray analyses the main rotamer of (+)-1 b and the meso-form (2 b) adopt crystal structures in which the bromine atoms come close to the CH₂-bridges. The torsional angles around the 2,2-bonds vary between 33°, 53° and 65° for (+)-1 b, racem.1 b and the mesoform2 b, respectively.Dedicated to Prof. Dr. G. Snatzke (Bochum) with cordial wishes on the occasion of the 60th anniversary of his birthday     

Isolation of stable enantiomerically pure telluroxides and their stereochemistry

Optical resolution of kinetically and thermodynamically stabilized diaryl telluroxides possessing bulky substituents (rac-1a-d) and amino group (rac-2a-c), respectively, by liquid chromatography using optically active columns yielded stable enantiomerically pure telluroxides. The absolute configurations of the optically active telluroxides were determined by comparing their specific rotations and CD spectra with those of sulfur or selenium analogues. The kinetics for the racemization of optically active telluroxides in solution was studied, and it was found that kinetic and thermodynamic stabilization were very effective preventing the racemization of telluroxides. The stabilization energy of telluroxides by intramolecular coordination of the amino group to the tellurium atom was estimated to be ca. 5 kcal mol-1 by variable temperature 1H NMR measurement. The mechanism for the racemization of optically active telluroxides was studied by an isotope experiment using H2(18)O, and the results indicated that optically active telluroxides underwent racemization via an achiral tetracoordinated hydrate.     

Efficient Synthesis and Practical Resolution of 1-(Naphthalen-1-yl)ethanamine,a Key Intermediate for Cinacalcet

An efficient synthesis of 1-(naphthalen-1-yl)ethanamine ( RS -2) and its practical resolution to optically pure (1R)-(naphthalen-1-yl)ethanamine ( R -(+)-2), a key intermediate in the synthesis of cinacalcet hydrochloride (1), is described. The resolution of RS -2 using R-(?)-mandelic acid as a resolving agent in ethanol was established on an industrial scale to give pure R -(+)-2 with >99.8% ee after liberation of the amine from its mandelate salt. An efficient process for the racemization of undesired isomer S -(?)-2 is also provided to maximize the yield of desired enantiomer.     

Pheromone, 1. Mitt.: (+)-cis-Disparlure: Synthese und Feldtests

Summary A synthesis of (+)-cis-disparlure is described starting from racemic 2-hydroxy-dodecannitrile (2), which is transformed into the O-protected enantiomerically pure cyanohydrine4. Grignardreaction followed by reduction with BH₃ · (CH₃)₂S yields the correspondingthreo-configurated secondary alcohol10. After tosylation and cleavage of theMBE-protective-group (+)-cis-disparlure (14) is obtained by treatment with KOH. Mating disruption field tests exhibited a significantly increased effectiveness of (+)-cis-disparlure as compared to the racemic product.

Unserem verehrten Lehrer Professor Dr. O. Hromatka zum 85. Geburtstag gewidmet     

Stereochemie von Metallocenen, 42. Mitt.: Optisch aktives π-Fluorenon-tricarbonylchrom — Darstellung,enantiomere REinheit,absolute Konfiguration und Versuche zur Racemisierung

Racemic Fluorenone-Cr(CO)₃ (1) was prepared from fluorenone ethyleneketal by complexation with Cr(CO)₆ and subsequent cleavage of the dioxolane9. Asymmetric reduction of1 with a chiral Lithium hydride afforded both (+)-1 and the correspondingendo-carbinol (–)-7 a with optical yields up to 80% as established by the use of chiral nmr shiftreagents. Active1 could also be obtained by two other asymmetric reactions albeit with low optical yields. LiAlH₄–AlCl₃ reduction of (+)-1 gave traces of (+)-fluorene-Cr(CO)₃ (2).The absolute chirality of (+)-1 was deduced as (S) by application of the abovementioned asymmetric reduction to ferroceno indenone (11) of known configuration and byHoreau's method to (–)-7 a. Several attempts to racemize1 failed, which proves that no transanular shift of Cr(CO)₃ takes place. The CD spectra of1 and2 are reported.Some side reactions such as the reduction of7 a to2 with Cr(CO)₆ in dibutylether (leading also to the formation of isomeric dimethylbenchrotrenes from the solvent) and the formation of a binuclear complex14 between1 and2 are briefly reported.

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41. Mitt.:M. Benedikt undK. Schlögl, Mh. Chem.109, 805 (1978).     

Preparation of (R)-(+)-lithium lactate

Summary Optically pure (R)-(+)-lithium lactate (7) and its benzyl ether analogue (6a) were obtained from acetaldehyde usingEliel's 1,3-trans-oxathiane (1) as the chiral auxiliary for chromatographic separation.

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Herstellung von (R)-(+)-Lithiumlactat

Zusammenfassung Optisch reines (R)-(+)-Lithiumlactat (7) und sein Benzyletheranaloges (6a) wurden mittelsEliels 1,3-trans-Oxathian (1) als chiralem Hilfsstoff zur chromatographischen Trennung aus Acetaldehyd hergestellt.

     

Syntheses and absolute stereochemistry of chiral 9,10-dihydro-9,10-ethanoanthracenes and their tricarbonylchromium complexes

Summary Several chiral mono- and disubstituted 9,10-dihydro-9,10-ethanoanthracenes have been prepared from the corresponding anthracenes. Most of them were separated into enantiomers by chromatography on cellulose triacetate (CTA) and their absolute chiralities established by chiroptical comparison (via their CD spectra) with key compounds of known configuration. From the laevorotatory 1,5-dibromo derivative16 the dextrorotatory dideuterio hydrocarbon (+)(9S, 10S)-20 was obtained.Complexation of 2,6-dimethyl 9,10-dihydro-9,10-ethanoanthracene (+)-25, obtained by enantio-selective chromatography onCTA [with its chirality (9R, 10R) deduced from optical comparison with the 2-monomethyl derivative of known configuration], with Cr(CO)₆ afforded two mono tricarbonyl-chromium complexes [endo(+)-26 andexo(+)-27] as well as the bis-exo,endo-complex (+)-28. Configurational assignments (exo, endo) are based on the absorption patterns of the bridge protons in the¹H-NMR spectra.On leave from Research Institute of Chemical Processing and Utilization of Forest Products, Nanking, P.R. China. mit Cr(CO)₆ lieferte zwei Mono-tricarbonylchrom-Komplexe [endo(+)-26 undexo(+)-27] neben dem Bis-exo,endo-Komplex (+)-28. Die konfigurative Zuordnung (exo,endo) war aufgrund der Absorptionen der Brücken-H-Atome in den¹H-NMR-Spektren möglich.     

Antioxidant phenolic compounds from the rhizomes of Astilbe rivularis

The rhizomes of Astilbe rivularis, commonly known as ‘Thulo Okhati’ are widely used in Nepal as tonic for uterine and menstrual disorders. In our preliminary study, the 70% MeOH extract of the rhizomes showed potent antioxidant activity. Hence, present study was aimed for the isolation of potent antioxidant constituents. Bergenin (1), 11-O-galloylbergenin (2), (+)-catechin (3), (?)-catechin (4), (?)-afzelechin (5), (?)-epiafzelechin (6) and 2-(β-D-glucopyranosyloxy)-4-hydroxylbenzenacetonitrile (7) were isolated from the rhizomes. Structures of these compounds were elucidated on the basis of spectroscopic methods. All these isolated compounds were evaluated for their in vitro antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. 11-O-Galloylbergenin (2), (+)-catechin (3), (?)-catechin (4), (?)-afzelechin (5) and (?)-epiafzelechin (6) showed potent antioxidant activity.     

Die Stereochemie der Irone

The 6 R configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (—)-camphor. (+)-cis-γ-irone [(+)- 4 ] was converted into (+)-cis-α-irone [(+)- 1 ], (?)-trans-α-irone [(minus;;)- 2 ], and (+)-β-irone [(+)- 3 ], which therefore also have the 6 R configuration. The 2 S configurations of (+)-cis-α-irone [(+)- 1 ] and (+)-trans-α-irone [(+)- 2 ] were determined by comparison of their circular dichroism with that of R-α-ionone [(+)- 5 ]. The 2 S configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (+)-cis-α-irone [(+)- 1 ].     

A new sesquiterpene from the entomogenous fungus Phomopsis amygdali

A new sesquiterpene, (+)-S-1-methyl-abscisic-6-acid (1), together with five known compounds, (+)-S-abscisic acid (2), fusicoccin J (3), 3α-hydroxyfusicoccin J (4), (R)-5-hydroxymethylmellein (5) and 4-hydroxyphenethyl acetate (6) was isolated from the fermentation extract of Phomopsis amygdali, an entomogenous fungus isolated from Call midge. Their structures were determined mainly by analysis of MS and NMR spectroscopic data. Compounds 1–6 were tested for antimicrobial activity against three plant pathogenic fungi: Gibberella zeae, Verticillium albo-atrum, and Fusarium nivale, and two bacteria: Escherichia coli and Pseudomonas aeruginosa 2033E. As a result, compounds 1–4 displayed antibacterial activity against Gram-negative P. aeruginosa 2033E, and the minimum inhibition concentration (MIC value) of 1–4 is 30 μg/mL, 58 μg/mL, 26 μg/mL, and 26 μg/mL, respectively.     

Total syntheses and antimicrobial activities of pyridine alkaloids from Rubiaceae

Summary Pyridine alkaloids from Rubiaceae were prepared by palladium-catalyzed cross-coupling reactions of methyl 5-bromonicotinate (6) with various organometallic reagents. Baker's yeast reduction of the ketone8 gave the levorotatory alcohol (S)-1. On this basis, the naturally occurring alcohol (+)-1 was assigned to be (R)-configurated. The alkaloids1 and4 show weak antimicrobial activities.

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Totalsynthesen und antimikrobielle Aktivität von Pyridin-Alkaloiden aus Rubiaceen

Zusammenfassung Pyridin-Alkaloide aus Rubiaceen wurden durch palladium-katalysierte Kupplungsreaktionen von 5-Bromnicotinsäuremethylester (6) mit verschiedenen organometallischen Verbindungen hergestellt. Reduktion des Ketons8 mit Bäckerhefe ergab den linksdrehenden sekundären Alkohol (S)-1. Daher weist der natürlich vorkommende Alkohol (+)-1(R)-Konfiguration auf. Die Alkaloide1 und4 besitzen schwache antimikrobielle Aktivität.

     

An Improved Synthesis of (+)-3,4-O-Isopropylidene Butyne

(+)-3, 4-O-Isopropylidene butyne ( 1 ) has been prepared in 81% isolated yield from (+)-2, 3-isopropyli-dene-D-glyceraldehyde ( 2 ) using a modified Corey-Fuchs procedure.     

Synthesis of novel chiral dopants based on optically active p-substituted mandelic acids

Novel esters of optically active p-substituted mandelic acids (+)-1 and (+)-2 were prepared by a convergent synthetic strategy in high enantiomeric excess (99% ee). The esters (+)-1 and (+)-2 induce helical macrostructures in the mesophases of achiral liquid-crystal materials, although neither exhibits mesorphism on its own.     

Konfigurative Zusammenhänge in der Muscarinreihe; Chiralität des epi-, allo- und epiallo-Muscarins,des Muscarons und allo-Muscarons. Zur biogenese des muscarins 37. Mitteilung über muscarin und verwandte stoffe

The chirality of all stereoisomeric muscarines has been determined. (–)-Muscarine chloride was converted to (+)-normuscarine, which in turn was oxidized to (+)-normuscarone. Epimerisation by acid catalysis of the latter gave a mixture of the C(2)-epimers, namely (+)-normuscarone and (–)-allo-normuscarone. From these were prepared by reduction with LiAlH₄ optically active stereoisomeric noralcohols. The natural stereoisomeric muscarines so far isolated are: (+)-(2S, 3R, 5S)-muscarine, (–)-(2S, 3R, 5R)-allo-muscarine and (+)-(2S, 3S, 5S)-epi-muscarine. Identical chirality appears only at C(2). This fact has to be taken into consideration for further speculations about the biogenesis of muscarines. Optically active muscarone and normuscarone exhibit a strong Cotton effect at 300 nm, which is interpreted in terms of absolute configuration by analogy to optically active substituted cyclopentanones. Optically active allo-normuscarone exhibits a very weak Cotton effect only, presumably because of predominant pseudo-rotation. The relative stability of the stereoisomeric norketones has been determined. Normuscarone (cis-2,5) is by 0,39 kcal/mol more stable than allo-normuscarone (trans-2,5).