Synthese von diastereo- und enantio-selektiv deuterierten β,ε-, β,β-, β,γ- und γ,γ-Carotinen

Synthesis of Diastereo- and Enantioselectively Deuterated β,ε-, β,β-, β,γ- and γ,γ-Carotenes We describe the synthesis of (1′R, 6′S)-[16′, 16′, 16′-²H₃]-β, εcarotene, (1R, 1′R)-[16, 16, 16, 16′, 16′, 16′-²H₆]-β, β-carotene, (1′R, 6′S)-[16′, 16′, 16′-²H₃]-γ, γ-carotene and (1R, 1′R, 6S, 6′S)-[16, 16, 16, 16′, 16′, 16′-²H₆]-γ, γ-carotene by a multistep degradation of (4R, 5S, 10S)-[18, 18, 18-²H₃]-didehydroabietane to optically active deuterated β-, ε- and γ-C₁₁-endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C₁₁ → C₁₄; C₁₄+C₁₂+C₁₄→C₄₀. NMR.- and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all-(E)-[²H₆]-β,β-carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.-effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′-²H₆]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.- and CD.-spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented.     

Stereoselectivity of the Diels-Alder Reaction of (E)-γ-Oxo-α,β-Unsaturated Thioesters with Cyclopentadiene

The stereoselectivity of the Diels-Alder reaction of (E)-γ-oxo-α,β-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d . In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 °C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75-94:25-6 respectively. The stereoelectivity was enhanced to ratios of 95-98:5-2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I₂ in aqueous THF at 0 °C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodo-lactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I₂ under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-γ-oxo-α,β-unsaturated thioester 2b was also examined.     

Synthesis of 5-phenylnaphtho[1,2-b]benzofuran by ambident alkylation of 1-naphthol

Reaction of 1-naphthol with 2-chlorocyclohexanone in alkaline alcohol gave as the major product 5-(2′-oxocyclohexyl)-7,8,9,10-tetrahydronaphtho[1,2-b]benzofuran ( 1 ), which could be converted to the title compound 5 by reduction and dehydrogenation. This product arises from ambident alkylation of 1-naphthol at the 2-and 4-positions. Via the 2′-oxocyclohexyl ether, 5 was also synthesized from 4-phenyl-1-naphthol.     

Totalsynthese von natürlichem α-Tocopherol. 1. Mitteilung. Herstellung bifunktioneller,optisch aktiver Synthesebausteine für die Seitenkette mit Hilfe mikrobiologischer Umwandlungen

Total Synthesis of Natural α-Tocopherol. I. Preparation of Bifunctional Optically Active Precursors for the Synthesis of the Side Chain by Means of Microbiological Transformations Our 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 ).     

Substituted γ-lactones. XXX. Reactions of α-Keto-β-Subtituted-γ-butyrolactones with diamines

The condensation reaction between α-keto-β-aroyl (or acyl) -γ-butyrolactones, 4a-4e and o-phenylenediamine or 2, 3-diaminonaphthalene leads under retrograde aldol condensation involving loss of formaldehyde to formation of 3-substituted-3, 4-dihydro-2 (1H) quinoxalinones or benzo [g] quinoxalinones, 7a-7g , respectively as a new convenient synthesis of this type of heterocyclic systems. The reaction of type 4 compound with 4, 5-diaminopyromidine, 8 , was found to proceed differently. 2-[(4-Amino-5-pyrimidinyl)amine]-4-oxo-3-(hydroxymethyl)-4-phenyl-2-butenoic acid 9 was the only product formed when the reaction between 4a and 8 was run in ethanol. The same reaction in glacial acetic acid proceeds with loss of formaldehyde, to afford 7-phenacylidene-7,8-dihydro-6 (1H)-pteridione 10 . The reaction between type 4 compounds and ethylenediamine or 1, 4-phenylenediamine leads to the formation of the bis-condensation products 13–15 , respectively.     

Studies on furan derivatives. V. A novel ethoxycarbonylmethylation of the 5-nitro-2-furan ring in the reaction of α-(2-furyl)-β-(5-nitro-2-furyl)ethynyl with N-ethoxycarbonylmethylpyridinium ylide

An unexpected product, 1-(4-ethoxycarbonylmethyl-5-nitro-2-furyl)-2-(2-furyl)-3-ethoxycarbonyl-indolizine was obtained by the reaction of α-(2-furyl)-β-(5-nitro-2-furyl)ethynyl with N-ethoxy-carbonylmethylpyridinium ylide in N,N-dimethylformamide, together with 1-(5-nitro-2-furyl)-2-(2-furyl)-3-ethoxycarbonylindolizine.     

Synthese makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung

Synthesis of Macrocyclic Lactones by Ring Enlargement Reaction Treatment of 3-(1-nitro-2-oxocyclohexyl)propanal ( 1 ) prepared by Michael addition of 2-nitrocyclohexanon and acrylaldehyde with methyltri (2-propoxy)tita-nium yielded a mixture of 2 and 3 which was converted into 6-nitro-9-decanolide ( 4 ).     

Photochemische Reaktionen 111. Mitteilung [1] Zur Photochemie α, β-ungesättigter γ, δ-Epoxyester I: Singulett- versus Triplettreaktivität

On triplet excitation (E)- 2 isomerizes to (Z)- 2 and reacts by cleavage of the C(γ), O-bond to isomeric δ-ketoester compounds ( 3 and 4 ) and 2,5-dihydrofuran compounds ( 5 and 19 , s. Scheme 1). - On singulet excitation (E)- 2 gives mainly isomers formed by cleavage of the C(γ), C(δ)-bond ( 6–14 , s. Scheme 1). However, the products 3–5 of the triplet induced cleavage of the C(γ), O-bond are obtained in small amounts, too. The conversion of (E)- 2 to an intermediate ketonium-ylide b (s. Scheme 5) is proven by the isolation of its cyclization product 13 and of the acetals 16 and 17 , the products of solvent addition to b . - Excitation (λ = 254 nm) of the enol ether (E/Z)- 6 yields the isomeric α, β-unsaturated ε-ketoesters (E/Z)- 8 and 9 , which undergo photodeconjugation to give the isomeric γ, δ-unsaturated ε-ketoesters (E/Z)- 10 . - On treatment with BF₃O(C₂H₅)₂ (E)- 2 isomerizes by cleavage of the C(δ), O-bond to the γ-ketoester (E)- 20 (s. Scheme 2). Conversion of (Z)- 2 with FeCl₃ gives the isomeric furan compound 21 exclusively.     

Nucleoside und Nucleotide. Teil 10. Synthese von Thymidylyl-(3′-5′) -thymidylyl-(3′-5′)-1-(2′-desoxy-β-D-ribofuranosyl)-2(1 H)-pyridon

Nucleosides and Nucleotides. Part 10. Synthesis of Thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D - ribofuranosyl)-2(1 H)-pyridone The synthesis of 5′-O-monomethoxytritylthymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1H)-pyridone ((MeOTr)T_dpT_dp∏_d, 5 ) and of thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridone (T_dpT_dp∏_d, 11 ) by condensing (MeOTr) T_dpT_d ( 3 ) and p∏_d(Ac) ( 4 ) in the presence of DCC in abs. pyridine is described. Condensation of (MeOTr) T_dpT_dp ( 6 ) with Π_d(Ac) ( 7 ) did not yield the desired product 5 because compound 6 formed the 3′-pyrophosphate. The removal of the acetyl- and p-methoxytrityl protecting group was effected by treatment with conc. ammonia solution at room temperature, and acetic acid/pyridine 7 : 3 at 100°, respectively. Enzymatic degradation of the trinucleoside diphosphate 11 with phosphodiesterase I and II yielded T_d, pT_d and p∏_d, T_dp and Π_d, respectively, in correct ratios.     

Thermische Lactonisierung von Estern γ-Brom-α, β-ungesättigter Carbonsäuren zu Δα-Butenoliden. Direkte γ-Bromierung von α, β-ungesättigten Säuren

By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ^7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δ^α-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δ^α-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δ^α-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δ^α-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δ^α-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δ^α-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δ^α-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.     

Chemical Synthesis,Proton NMR. Parameters,Hydrogen- and Calcium-Ion. Complexation of L-γ-Carboxyglutamyl-L-γ-carboxyglutamic Acid and D-γ-Carboxyglutamyl-L-leucine

The purpose of this communication is to describe the preparation and some properties of the first two synthetic peptides containing D - and L -γ-carboxyglutamic acid. Use was made of N-protected γ,γ′-di-t-butyl-γ-carboxyglutamic acids (D , L , and DL ) described earlier [1 a]. Preliminary ¹H-NMR. data (360 MHz) indicate a restricted rotation of the Gla side chain in the free amino acid as well as in the C-terminal Gla of Gla-Gla in H₂O solution at acid pH. The proton dissociation from Gla and Gla-Gla was studied by potentiometric titration and NMR. methods. The pH titration in the presence of Ca²⁺ ions shows that Gla-Gla has a much higher association constant for this cation than Gla. It is almost as great as that of prothrombin (pCa²⁺ = 3.2 vs. 3.5).     

The transformation using the soft NO⊕-species

The reaction of NaNO₂ in acidic solution with thiocarbonyl compounds has been studied. Secondary- and tertiary thioamides, 1-benzyl-hexahydro-2H-azepine-2-thione, 5-ethyl-5-phenyl thiobarbituric acid, certain thiourea derivatives, 2H-1-benzopyran-2-thione, O,O-diphenyl-thiocarbonic ester, O,S-diphenyl-dithiocarbonic ester, N,N-dimethyl-S-phenyl-dithiocarbamatic ester, N-ethyl-N-phenyl-O-ethyl-thiocarbamatic ester are all converted into the corresponding carbonyl-analogues. 4,4′-Bis (dimethylamino)-thiobenzophenone (Michler's thioketone) gives 3-nitro-4,4′-bis (dimethylamino)-benzophenone at room temperature. At (?10 °C)-(?5 °C) the expected oxo compound is obtained as the main product together with 4-(N-nitroso-methylamino)-4′-(dimethylamino)-benzophenone.     

3-(2-氧代环烷基)丙酸与(R)-2-硫代四氢噻唑-4-羧酸乙酯的反应

３－（２－氧代环烷基）丙酸与（Ｒ）－２－硫代四氢噻唑－４－羧酸乙酯的反应李叶芝,田颜清,黄化民（吉林大学化学,长春,１３００２３）关键词（Ｒ）－２－硫代四氢噻唑－４－羧酸乙酯,Ｎ－３－（２－氧代环烷基）丙酰－２－硫代四氢噻唑－４－羧酸乙酯,环合反应,...     

Die Oxidation von 3-(1-Nitro-2-oxocycloalkyl)propanal

The Oxidation of 3-(1-Nitro-2-oxocycloalkyl)propanal Oxidation of the title compound 1 with KMnO₄ under neutral conditions led to the corresponding acid 2 , 5-(2,3,4,5-tetrahydro-2-nitro-5-oxo-2-furyl)pentanoic acid ( 4 ), and 4-oxononadioic acid ( 6 ). On the basis of experimental results the mechanism of the formation of 4 is discussed (Scheme 1). Oxidation of 1 with KMnO₄ under basic conditions gave 6 which was transformed to (E)-4,5-dihydro-5(2′-oxocyclopentyliden)furan-2(3H)-one ( 12 ) with benzene/TsOH (Scheme 3). In contrast to this result the corresponding 4-oxoheptandioic acid ( 22 ) yields 1,6-dioxaspiro[4,4]nonan-2,7-dione ( 23 ) only (Scheme 4).     

Investigations Concerning an Unexpected Reaction between the Dimsyl Anion ( = (Methylsulfinyl)methanide) and a γ,δ-Epoxy-ketone

The reaction of 2,2-dimethyl-5-(1,2-epoxypropyl)cyclohexanone ( 7 ) with t-BuOK in DMSO furnished a small amount of 5-(1-hydroxyprop-2-enyl)-2,2-dimethylcyclohexanone ( 12 ) and the 4 unexpected products 13–16 which contain one to three additional C-atoms (Scheme 2). The relative configuration of the major product 1-(4′,4′-dimethyl-2′,3′-dimethylidenecyclohexyl)propane-1,2-diol ( 15 ) was shown to be 1RS, 2RS,1′SR via NOE measurements performed on a derivative thereof. A crossover experiment in DMSO/[¹³C₂]DMSO 1:1 as solvent showed that the two additional C-atoms of this product originate from a single molecule of DMSO (Scheme 5). A tentative mechanistic scheme, consistent with all experimental observations, is proposed which involves a [2,3]-sigmatropic rearrangement of an (allylsulfinyl)methanide to a sulfenic acid as one of the key steps ( V → 24 , Scheme 8). We corroborated part of this hypothetic scheme by taking recourse to a model compound (7-(methylsulfinyl)-p-mentha-1,8-diene ( 32/33 ), readily prepared in two steps from perilla alcohol ( 30 )), which reacted as predicted by the proposed mechanism (Schemes 9 and 10).     

Nitration of 2,3′-bithienyl

The nitration of 2,3′-bithienyl ( 1 ) with fuming nitric acid in acetic anhydride at 0° gives a mixture of 3-nitro- ( 2 ), 2′ -nitro- ( 3 ) and 5-nitro-2,3′-bithienyl ( 4 ) with relative percentages of 38.7%, 34.8% and 26.5%. When the nitration of 1 was carried out with fuming nitric acid in acetic acid at 20°, the same compounds 2, 3 and 4 were obtained, but with different relative percentages: 20.4%, 36.5% and 43.1% respectively. The results of the mononitration of 1 are compared with those obtained in other electrophilic substitutions and with the theoretical predictions. The further nitrations of 2, 3 and 4 with nitric acid in acetic anhydride at room temperature lead to the formation of five dinitro-2,3′-bithienyl isomers. Compound 2 gives a mixture of 2′,3-dinitro- ( 5 ) and 3,5′-dinitro-2,3′-bithienyl ( 6 ); compound 3 gives a mixture of 5 , 2′,5-dinitro- ( 7 ) and 2′,4-dinitro-2,3′-bithienyl ( 8 ); compound 4 gives 7 and 5,5′-dinitro-2,3′-bithienyl ( 9 ). The possible reasons of the formation of the various dinitro-2,3′-bithienyl isomers are discussed.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXIX The crystal and molecular structure of 5-(3′-hydroxypyridyl-2′-thio)-4-nitro-1-methylimidazole

Reaction of the dianion of 3-hydroxypyridine-2(1H)-thione with 5-chloro-4-nitro-1-methylimidazole in N,N-dimethylformamide led to the formation of 5-(3′-hydroxypyridyl-2′-thio)-4-nitro-1-methylimidazole, which failed to cyclize to the desired pyrid[1,4]oxathiinoimidazole derivative. In an effort to determine why the intermediate phenolate sulfide had failed to cyclize, the crystal structure of the isolated product was determined. The structure refined to R = 0.036.     

Acid-Catalysed Rearrangements of α-Vinylcyclobutanones

The BF₃ · Et₂O- and the CH₃SO₃H-catalysed rearrangements of 10 α-vinylcyclobutanones have been examined. With little acid, the β,β-dialkyl derivatives 1 were transformed into linear dienones 2 and 3 ; with more acid, they were converted into cyclopentenones 4 by Nazarov cyclisation of initially formed 2/3 . The β-monoalkyl (including the β,γ-dialkyl) derivatives 7 rearranged only with a high acid concentration to afford the cyclopentenones 8 by 1,2-acyl migration. In the case of 7a , the cyclopentenone 8a was accompanied by the unexpected constitutional isomer 9a , which is explained by a reversible interconversion of the cyclobutanone 7a with its isomer 19 via a cyclopropane intermediate like 18 . In the case of the β,β-dialkyl derivative 5 , which contains an α-isobutenyl (instead of an α-vinyl) group, the acid-catalysed rearrangement product was the bicyclo[3. 1. 0]hexanone derivative 6 .     

Struktur des Zwischenproduktes einer (i-PrO)2 TiMe2-Methylierung: NMR-Untersuchungen und Konformationsanalyse

Structure of the Intermediate of a Methylation with (i-PrO)₂TiMe₂: NMR Investigations and Conformational Analysis The intermediate of the reaction of 3-(1-nitro-2-oxocyclohexyl)propanal ((±)- 1 ) with (i-PrO)₂TiMe₂ was shown to be a titanium salt of 6-(hydroxynitroryl)decano-9-lactone. ¹H-, ¹³C-, HSQC-, ¹H,¹H-TOCSY- and long-range HMBC-NMR spectra of this intermediate indicate a complexation of the carbonyl O-atom and an O-atom of the hydroxynitroryl group to the same Ti-atom. The product of the reaction (t-3-methyl-c-6-nitro-2-oxabicyclo[4.4.0]decan-r-1-ol, (±)- 2 ) was reacted with several titanium reagents to give also titanium salts of the 6-(hydroxynitroryl)decano-9-lactone. Monte Carlo studies and MM3^* force-field calculations of the anion of 6-(hydroxynitroryl)decano-9-lactone, 3′ , resulted in a conformation of the ten-membered ring (only 9.57 kJ/mol higher in energy than the global minimum), which allows the Ti-atom to coordinate to the O-atom of the N(O)OH and C?O group at the same time. With the suggested structure of 3′ · TiR_n, we are able to explain the selectivity of the reaction.     

Totalsynthese von natürlichem α-Tocopherol. 2. Mitteilung. Aufbau der Seitenkette aus (−)-(S)-3-Methyl-γ-butyrolacton

Total Synthesis of Natural α-Tocopherol A short and efficient route to optically pure (+)-(3 R, 7 R)-trimethyldodecanol ( 14 ) is demonstrated, 14 serving as side chain unit in the preparation of natural vitamin E. The synthesis of 14 is based on the concept of using a single optically active C₅-synthon of suitable configuration and functionalization to introduce both asymmetric centres in 14 . (?)-(S)-3-Methyl-γ-butyrolacton ( 1 ) and ethyl (?)-(S)-4-bromo-3-methylbutyrate ( 2 ), respectively, is used in a sequence of either two Grignard C,C-coupling reactions 5 → 8 and 12 → 13 or two Wittig reactions 17a → 18 and 20 → 21 to achieve this goal. 14 is converted to (2 R, 4′R, 8′R)-α-tocopherol (= vitamin E) by coupling with a chroman unit in known manner. Optical purity of products and intermediates is established.