9-acetoxyanthracene derivatives. Part VIII. The mechanism of degradation of 9-acetoxy-10-arylanthracenes to anthraquinone

The mechanism of degradation of 9-acetoxy-10-arylanthracenes to anthraquinose with the use of HNO₃ in AcOH has been reported. This was proved by way of example on 9-acetoxy-10-(4′-acetoxyphenyl )anthracene (1) by means of separation and identification of intermediate products $\text{2}$, $\text{3}$ and $\text{4}$.     

The absolute configurations of (+)-thalictrifoline and (+)-corydalic acid methyl ester. Total synthesis of (+)-thalictrifoline.

(+)-Thalictrifoline ($\text{3}$) has been synthesized from an optically resolved (+)-8-oxo-13-carboxytetrahydroprotoberberine ($\text{13}$) whose absolute configuration was established by correlation with (+)-$\text{18}$. This determines the absolute configurations of (+)-thalictrifoline ($\text{3}$) as 13R, 14R aria (+)-corydalic acid methyl ester ($\text{9}$) as 3R, 4R.     

Athrotaxis alkaloids. Part I. Alkaloids of A. Cupressoides

Eleven homoerythrina-type alkaloids ($\text{tilda1}$-$\text{tilda9}$, $\text{tilda11}$, $\text{tilda12}$) have been isolated from A. cupressoides (Taxodiaceae), of which six ($\text{tilda6}$-$\text{tilda9}$, $\text{tilda11}$,$\text{tilda12}$) had not previously been reported.     

Models that demonstrate peptide bond formation by prior thiol capture I. Capture by disulfide formation

Unsymmetrical disulfides formed from $\text{L}$-cysteine esters and $\text{o}$-Cbz-$\text{L}$-alaninyloxy-benzenethiol $\text{9}$, 2-Cbz-$\text{L}$-alaninyloxy-5-chlorophenylmethylenethiol $\text{8}$,4-acetoxyxanthenylmethylene thiol $\text{10}$, and 1,5-diacetoxy-2-methyl-3-methoxy-4-thioxanthone $\text{11}$ are observed to undergo intramolecular O,N-acyl transfer in yields up to 60%, with accompanying disulfide interchange. The significance of these results for a general amide forming strategy of prior cysteine capture are discussed.     

Occurrence of 9(11)-ussaturated sterol peroxides in tunicates.

New natural 9(11)-unsaturated steral $\text{1}$, $\text{2}$, $\text{3}$, $\text{4}$ have been isolated from marine Tunicates (Urochordates). Structure elucidation was based on spectral data and confirmed by synthesis.     

Synthesis of phosphatidyl-α-glucosyl glycerol containing a dioleoyl phosphatidyl moiety. Application of the tetraisopropyldisiloxane-1,3-diyl (tips) protecting group in sugar chemistry. part III1

In this study we demonstrate that the tetraisopropyldisiloxane-1,3-diyl protecting group could be introduced, in a two step procedure, at the 3'- and 4'-hydroxyl functions of α-glucosyldiglyceride $\text{3}$ to give derivative $\text{6}$. Compound $\text{6}$ could be selectively condensed with a suitably protected phosphatidyl part $\text{9}$ at its primary hydroxyl function to afford the protected glycophospholipid $\text{10a}$. The phosphatidyl part $\text{9}$ was obtained by phosphorylation of optically pure 1,2-di-O-oleoyl-sn-glycerol ($\text{8a}$) with phosphoditriazolide $\text{7b}$. Finally, the 2,4-dichlorophenyl and TIPS protecting groups were removed from $\text{10a}$ by syn-4-nitro-benzaldoximate and fluoride ions, respectively, to afford glycophospholipid $\text{10c}$.     

Isolation ofΔ9(11)-sterols from the sea cucumber psolusfabricii. Implications for holothurin biosynthesis

- 14α-Methyl-5α-cholest-9(11)-en-3β-ol ($\text{2}$) and 4α,14α-dimethyl-5α-cholest-9(11)-en-3β-ol ($\text{3}$) have been isolated from the sea cucumber $\text{Psolus}$$\text{fabricii}$ and characterised by ¹H NMR, ¹³C NMR and mass spectrometry. Lanost-9(11)-en-3β-ol ($\text{4}$) has also been tentatively identified. The relevance of this series of Δ⁹⁽¹¹⁾-sterols to holothurin biosynthesis is briefly discussed.     

Studies on the syntheses of heterocyclic and natural compounds. Part 939: An efficient and stereoselective synthesis of des-a-ring steroids—potential intermediates to estradiol,cortisone and progesterone

A stereoselective synthesis of des-A-ring steroids $\text{9}$ and $\text{17}$ has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2-one-2-ethylene ketal $\text{7}$ and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol $\text{16}$, respectively.     

Conversion of adenosine to a pentacyclic structure by a 4-nitroquinoline-1-oxide metabolite model.

A new pentacyclic compound $\text{2A}$ has been obtained from the reaction of adenosine $\text{1}$ with 1-acetoxy-4-(acetoxyimino)-1,4-dihydroquinoline $\text{3}$, a model for the ultimate metabolite of the carcinogen 4-nitroquinoline-1-oxide. 9-propyladenine $\text{5}$ gives an analogous pentacyclic product $\text{6A}$ whose crystal structure has been determined.     

Nitrogen bridgehead compounds part 12. The reaction of the ethyl 6-methyl-4--oxo-6,7,8,9-tetrahydro-4h-pyrido [1,2-a]pyrimidine-3-carboxylate with iminium chlorides.

The 9-formyl- and 9-ester derivatives /$\text{5}$,$\text{9}$/ can easily be prepared from the title pyrido [1,2-a]pyrimidine /$\text{1}$/ with iminium chlorides /$\text{2}$a,b/ via the 9-/dimethyliminium-methyl/-derivatives /$\text{3}$,$\text{6}$/.     

Activation and transfer of oxygen XV evidence for the transient opening of the pyrazine ring in n1- and n5- alkylflavin models. 4a- to 1010- adduct isomerization and pyrazine- and pyrimidine- ring contractions.

The pyrazine ring opening is proven by rearrangements leading to benzimidazoles $\text{4}$, $\text{13}$ and $\text{14}$. A 4^a- to 10^a-adduct isomerization ($\text{6}$ → $\text{7}$) and the intermediacy of a carbonyl oxide $\text{15}$ are indicated by pyrimidine ring contractions into $\text{8}$ and $\text{9}$, respectively.     

Biomimetic approach to the synthesis of rhodolaureol and rhodolauradiol

It is postulated that 9-hydroxy-β-iso-obtusene ($\text{4}$) is the biogenetic precursor of the tricyclic sesquiterpenoids rhodolauradiol ($\text{7}$) and rhodolaureol ($\text{9}$). The transformation $\text{4}$→$\text{7}$ was carried out under non-enzymic conditions.     

Regioselektive synthese von daunomycinon und γ-rhodomycinon

Synthesis of daunomycinone ($\text{2}$) and γ-rhodomycinone ($\text{3}$) by regioselective addition of the Grignard reagents $\text{9b}$ and $\text{9d}$ to the anhydride $\text{4}$.     

Investigations on diazo compounds and azides- LXII.: Synthesis and reactions of a-diazo phosphonates with a conjugated 1,3-diene unit

α-Diazo phosphonates with a conjugated 1,3-diene unit are synthesised by the Bamford-Stevens reaction ($\text{2}$ →$\text{4}$→$\text{3}$). They undergo [4+2]-cycloadditions with the dienophile $\text{5}$ to form the tetrahydrotriazolopyridazines $\text{8}$, which possess an unchanged diazo group. In contrast, dimethyl acetylenedicarboxylate ($\text{9}$) reacts exclusively with the diazo dipole of $\text{3}$ to yield the 3H-pyrazoles $\text{10}$, which rearrange to $\text{11}$ by sigmatropic PO-shifts and hydrolyse to form $\text{13}$. The diazo compound $\text{3b}$ isomerises to the pyrazole $\text{16}$ when heated in benzene.     

Cycloaddition of diphenylnitrilimine to coumarins. The synthesis of 3a,9b-dihydro-4-oxo-1H-benzopyrano [4 ,3-c]pyrazole derivatives

The cycloaddition of diphenylnitrilimine to a series of coumarins occurs with the same regioselectivity in all cases, regardless the nature of the substituent present, to yield the corresponding 3a,9b-dihydro-4-oxo-lH-benzopyrano [4,3-c]pyrazoles $\text{4}$a–f. Dehydrogenation of $\text{4a}$ yields 4-oxo-1H-benzopyrano [4,3-c]-pyrazole $\text{6}$. In ethanolic sodium ethoxide solution, the reaction between coumarin and diphenylnitrilimine precursor, namely N-phenylbenzohydrazidoyl chloride $\text{1}$, affords no cycloadducts, but yields o-(β-ethoxycarbonylvinyl)phenyl N-phenylbenzohydrazidate $\text{10}$. The regiochemistry of the cycloadducts $\text{4}$a–f and the reaction sequence leading to $\text{10}$ are outlined. The structures of the products have been established by spectroscopic methods and independent syntheses wherever possible.     

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.     

The Mannich reaction of 9-acetyl- and 9,10-dihydro-9-acetylanthracene. Reduction of the Mannich bases, and stereochemistry of the 9,10-dihydro compound

The Mannich derivatives ($\text{2}$ and $\text{5}$) of 9-acetyl-9,10-dihydroanthracene ($\text{4}$) with amines of different sizes were prepared for study of their biological effects. It was found that formation of the normal Mannich product in acetic acid was accompanied by formation of a secondary Mannich product containing a methylidene group ($\text{3}$ and $\text{6}$). Reduction of compounds $\text{5}$ with NaBH₄ gave aminoalcohols ($\text{10}$), and amino-olefins ($\text{11}$) were prepared from these by elimination. The catalytic reduction of compounds $\text{2}$ on Pd/C, Raney Ni and Adams catalysts was studied under acidic and basic conditions. In acidic media on Pd/C, the 9,10-dihydro compounds ($\text{5}$) were formed; under basic conditions, on all three catalysts the hydrogenation led to deamination. However, for “steric hindrance” reasons the keto group was not reduced in any of the cases. In compounds $\text{5}$, the literature data and the H-NMR spectra indicate that the orientation of the 9-substituent is pseudoaxial     

Synthesis of “9-deazaadenosine”; A new cytotoxic C-nucleoside isostere of adenosine

The synthesis of 7-(β-$\text{D}$-ribofuranosyl)-4-amino-5H-pyrrolo[3,2-$\text{d}$]pyrimidine (9-deazaadenosine) $\text{9}$ is described. It involves base-catalyzed cyclization of N-carboethoxyenamine $\text{4}$ to give β- and α-ribosylated 3-amino-2-cyanopyrroles $\text{6}$ and $\text{7}$, respectively, followed by a one-step conversion to the desired pyrrolo[3,2-$\text{d}$]pyrimidine system.     

Cyclopropylidene formation in 7,7-dibromonorcar-3-ene oxides. Synthesis of derivatives of homobenzvalene oxide.

Treatment of $\text{4b}$, $\text{4c}$, and $\text{4d}$ with methyllithium affords $\text{5b}$, $\text{6b}$; $\text{5c}$, $\text{6c}$; and $\text{5d}$ respectively in serviceable yields $\text{via}$ carbenoid cyclization.     

Cyclisierungen unter beteiligung von fluoridionen. 2. Mitteil. [1], [2]. 4.5-perfluor-1.3-dioxolane

4.5-Perfluoro-1.3-dioxolanes $\text{2}$ are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides $\text{3}$ or -ketone $\text{9}$ with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in $\text{2}$ can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives $\text{16}$ the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes $\text{18}$ are formed by reaction with triethylamine- hydrofluoride.