Studies on 1-carbadethiacephems, part II: Reaction of 4-acetoxy-2-azetidinone with aluminium enolates

A procedure for the novel reaction of αβ-unsaturated ketones (as zinc-free aluminium enolates) with 4-acetoxy-2-azetidinone, giving products $\text{2}$, is reported. A 1-carbadethia-2-oxocephem derivative $\text{5}$ has been prepared from compound $\text{2b}$.     

A novel deaminative cyclization of aminoglycoside. Synthesis of a kanamycin B variant having 2-oxa-5-azabicyclo[2,2,2]oct-1,5-diene ring

The 3′,5′-diene derivative of kanamycin B ($\text{2}$) was obtained from a 4′-ene derivative of kanamycin B ($\text{1}$) by treatment with trimethyl orthoacetate. Formation of the title compound ($\text{4}$) from $\text{2}$ deaminative cyclization with sodium methoxide followed by treatment with trifluoroacetic acid was described.     

New synthesis of benzo [a]quinolizidin-2-ones via protected 2-aryl-4-piperidones

A new synthesis of 9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-benzo aquinolizin-2-one ($\text{1a}$ and its 3-ethyl derivative $\text{1b}$ via the corresponding 2-(3,4-dimethoxyphenyl)-4-piperidone ethylene acetals $\text{7}$ is reported. Alkylation of 2-arylpipendires $\text{7}$ with 2-bromoethanol followed by oxidation of the resulting amino alcohols $\text{9}$ with oxalyl chloride and dimethyl sulfoxide afforded the aldehydes $\text{10}$, which were cyclized with hydrochloric acid to give 7-hydroxybenzo[α]quinolizidines $\text{11}$. The reduction of $\text{1}$ with trinethylsilane and subsequent acid hydrolysis led to benzo aquinolizidin-2-ones $\text{1}$.     

Stereospecific synthesis of (5E)-PGE2 by palladium-catalyzed decarboxylative 2-alkenylation of 2-alkenyloxycarbonylated cyclopentanone derivative

(5$\text{E}$)-Prostaglandin E₂ methyl ester was synthesized from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by $\text{in}$$\text{situ}$ 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ($\text{E}$)-2-butenylated cyclopentanone derivative was obtained from either 2-[($\text{E}$)- or ($\text{Z}$)-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition.     

Directed metallations of 4-ethylidenetetronic acid and its derivatives as a synthetic entry to natural 4-oxy-2-furanones

Lithium diisopropylamide (LDA) removes the α-proton from the O-methyl tetronic acid (2$\text{b}$) leading to the vinylic carbanion (12), whereas treatment of the trimethylsilyl derivative (14) with LDA, followed by reaction with aldehydes gives products resulting from both γ? and ε-addition; the directed metallations provide access to a range of 4-oxy-2-furanone derivatives found amongst natural products.     

Synthesis of trans-(3S,4S)-dibenzyloxycyclopentanone

The 1-cyano-1-thiophenylcyclopentone derivative $\text{1}$, obtained from (R,R)-(+)-tartaric acid, has been converted into a number of derivatives including the important $\text{trans}$-(3S,4S)-dibenzyloxycyclopentanone $\text{2}$ in 45% overall yield.     

Nucleosides-126: Selective methylation of the C-nucleoside, ψ-isocytidine and its 2$́-deoxy analog. Synthesis of 1-methyl, 3-methyl and 4-o-methyl derivatives

Methods were developed to prepare 1 -methyl-, 3-methyl- and 4-0-methyl-ψ-isocytidine by selective methylation.3$\text{,}\text{?}$5$\text{-}\text{?}$O-Tetraisopropyldisiloxanyl-ψ isocytidine (8) was trimethylsilylated and then treated with MeI and, after deprotection, 1 -methyl-ψ isocytidine (6) was obtained. The 2$\text{-}\text{?}$deoxy analog (7) was also prepared in a similar manner from the 2$\text{-}\text{?}$deoxy analog (10) of 8. Treatment of 8 with CH₂N₂ afforded the 3-methyl-ψ-isocytidine derivative (19) as the major product. Methylation with diazomethane also occurred mainly on N3 of the 2$\text{-}\text{?}$deoxy analog 10 to form 20. Removal of the 3$\text{,}\text{?}$ 5$\text{-}\text{?}$O-protecting group from 19 and 20 afforded 3-methyl-ψ-isocytidine (14) and its 2-deoxy analog (15), respectively. 2-N-Acetyl- 3$\text{,}\text{?}$5$\text{-}\text{?}$O-tetraisopropyldisiloxanyl-ψ-isocytidine (24), on the other hand, gave the 4-O-methyl derivative (25) as the major product upon CH₂N₂ treatment. Subsequent deprotection of 25 afforded 4-O-methyl-ψ-isocytidine (29). aiv51b1p33b     

Structure elucidation and synthesis of (2s)-4-oxo-1-azabicyclo[3.3.0]octa-5,7-diehe-2-carboxylic acid,a new metabolite isolated ercm stheptomyces oliyacbjs

The structure of a new metabolite isolated from $\text{Streptomyces}$$\text{olivaceus}$ has been shown to be (2S)-4-oxo-1-azabicyclo[3.3.0]octa-5,7-diene-2-carboxylic acid by means of its spectroscopic properties and total synthesis.     

Syntheses and thermal reactions of 2-alkyl(or aryl)-1-benzoyl-3,4-dihydro-2-thianaphthalenes

1-Benzoyl-2-methy1-3,4-dihydro-2-thianaphthalene ($\text{4a}$) underwent novel intermolecular 1,4-rearrangement in refluxing toluene to give an enol ether $\text{5a}$, while rearrangement of 2-phenyl derivative $\text{4e}$ proceeded intramolecularly in refluxing xylene to afford a 1,4-rearranged enol ether $\text{5b}$. On the other hand, ylides $\text{4a–e}$ were refluxed in alcohols to afford some ring-opened products $\text{10–12}$.     

Regioselective synthesis of 4-alkylquinolines from quinoline via 1-ethoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates

1-Ehtoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates ($\text{3}$) were treated with n-butyllithium followed by alkyl halides to afford the corresponding 4-alkylated phosphonates ($\text{7}$) with complete regioselectivity in 67–97% yields. The phosphonates ($\text{7}$) were converted to 4-alkylquinolines ($\text{8}$) in ca. 50% yields by treatment with sodium iodide in HMPA or by alkaline hydrolysis in aqueous ethanol.     

Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale

C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers $\text{2}$ to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses $\text{1}$ followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether $\text{2a}$ reacts with 2-acetoxy-3-keto-glycal derivative $\text{la}$ forming only one product $\text{3a}$. Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.     

Photoinitiated substitution reactions of 2 and 4-pyridinecarbonitrile with cyclopentene

The photoreactions of 4 and 2-pyridinecarbonitrile with cyclopentene carried out in acetone or in acetonitrile solutions lead, respectively, to 4-(2 cyclopentenyl)-pyridine $\text{1}$ and 2-(2 cyclopentenyl)pyridine $\text{2}$. From 2-pyridinecarbonitrile a little amount of ketone $\text{3}$ is obtained.     

Conformational behaviour and inclusion compound forming properties of 5,18-disubstituted derivatives of 5, 11, 12, 18-tetrahydrotribenzo[b,f,j][1,4]diazacyclododecine-6, 17-dione

An X-ray structure analysis shows that the 5, 18-dimethyl derivative ($\text{5}$) of the title compound ($\text{4}$) crystallises from xylene as a 1:1 inclusion compound in which the host molecules adopt propeller-like conformations ($\text{7}$ and $\text{7}$*) with almost perfect $\text{C}$₂ symmetry. Dynamic ¹H n.m.r. spectroscopy shows that the 5, 18-dibenzyl derivative ($\text{6}$) of ($\text{4}$) forms a 1:1 inclusion compound with ethanol in the solid state and undergoes ring inversion ($\text{7}$ ? $\text{7}$*) between enantiomeric propeller-like conformations in solution against a barrier of 21.1 kcal mol^?1     

From penicillin to penem and carbapenem. III C1-unit introduction at C-4 position of azetidinone

Monocyclic β-lactams ($\text{1}$) were converted into 4-cyano derivative $\text{2}$ (C₁-unit introduction) under two phase reaction conditions. The cyano group in $\text{2}$ was successively transformed into $\text{3}$ and $\text{4}$, which are thought to be important precursors for the carbapenem synthesis.     

Regiospecific alkylation of tetronic acids : Formation of 4-alkoxy-5H-furan-2-ones and 2-alkoxy-5H-furan-4-ones

2-Alkoxy-5$\text{H}$-furan-4-ones (7,8) and 4-alkoxy-5$\text{H}$-furan-2-ones (4,5) were prepared regiospecifically and in high yields from tetronic acids (4-hydroxy-5$\text{H}$-furan-2-ones) (2) in the first case by acetylating the 4-OH group and then reacting with trialkyloxonium tetrafluoroborate, and in the second case by alkylating tetrabutylammonium tetronates with dialkyl sulfate, respectively. Direct alkylation of tetronic acids with trialkyloxonium tetrafluoroborate gave in four cases regiospecific 2-O-alkylation, in one case 4-O-alkylation and in two other cases mixtures of 2- and 4-alkoxy derivatives.     

4-thioxo-2-azetidinones by cycloaddition of thioketenes with isocyanates

The (2+2) cycloaddition of thioketenes $\text{1}$ with isocyanates $\text{2}$ yields 4-thioxo-2-azetidinones $\text{3}$, which can be hydrolyzed to the N-unsubstituted compound $\text{4}$ and thus used as versatile intermediates.     

The crystal structure of Ca6Eu2Na2(PO4)6F2

The crystal structure of Ca₆Eu₂Na₂(PO₄)₆F₂ has been determined by single crystal X-ray diffraction. The unit cell constants are $\text{a = 9.385(2), c = 6.893(3)}\text{A}\text{?}$ and the space group is $\text{P6}{}_3\text{m}$. The structure was refined by normal full matrix least squares techniques. The final value of the refinement indicator is R = 0.065, based on 419 reflections.The structure of Ca₆Eu₂Na₂(PO₄)₆F₂ contains disordered cations in both the triangle and column positions. The occupation of the six triangle sites is $\text{1}\text{4}\text{Eu}$ and $\text{3}\text{4}\text{Ca}$ and of the four column sites $\text{1}\text{2}\text{Na}\text{,}\text{4}\text{10}\text{Ca}$, and $\text{1}\text{10}\text{Eu}$.     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

Synthesis of 4a-, 4e-phenyladamantanones and 2,4-o-benzenoadamantane by π-route

The acid catalysed reaction of 4-oxa-homoadamantan-5-one ($\text{1}$) with benzene yielded a mixture of 4^a-phenyladamantan-2-one ($\text{7}$), the equatorial isomer' ($\text{8}$) and 2-phenyl-2,4-o- benzenoadamantane ($\text{9}$) A plausible reaction pathway for the occurrence of $\text{9}$. is put forward. The structure of $\text{9}$, was deduced from spectroscopic data and reaction of the proposed intermediate 2,4^a-diphenyladamantan-2-ol ($\text{11}$) with acid. 2,4-o-Ben-zenoadamantane ($\text{16}$) is prepared likewise.