Showing papers in "Journal of The Chemical Society C: Organic in 1969"
TL;DR: Tri-O-acetyl-D-glucal undergoes complete reaction with alcohols in benzene solution in the presence of boron trifluoride to give 4,6-di-OðOðAðEðDÞÞ −2,3-dideoxy-α-DÒÞ−EðE Þ−hex-hex-2-enopyranosyl as discussed by the authors, which can be used to prepare the known crystalline ethyl αglucoside easily and in greatly improved
Abstract: Tri-O-acetyl-D-glucal undergoes complete reaction with alcohols in benzene solution in the presence of boron trifluoride to give 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranosides. The α-anomers predominate (ca. 90%), and the method can be used to prepare the known crystalline ethyl α-glucoside easily and in greatly improved yield. Other alkyl glycosides have been prepared similarly, and the procedure has afforded means of obtaining the cholesteryl analogue and the disaccharide derivative 6-O-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranosyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. Tri-O-acetyl-D-glucal again gave the 2,3-unsaturated glycosides on treatment with acetals in the presence of boron trifluoride; no evidence was obtained for the formation of branched-chain products produced by additions to the double bond.
179 citations
TL;DR: In this paper, a method for converting alkaloids having the dehydropyrrolizidine ring, and their N-oxides, to dihydroparrolizine derivatives, which are also formed as metabolites when the alkaloid are administered to animals, is described.
Abstract: Methods are described for converting alkaloids having the dehydropyrrolizidine ring, and their N-oxides, to dihydropyrrolizine derivatives, which are also formed as metabolites when the alkaloids are administered to animals. Some properties of these products are described. They behave as pyrrole derivatives, and those which are esters are highly reactive alkyiating agents, which are probably responsible for toxic effects of the alkaloids.
98 citations
TL;DR: In this paper, the tris-(p-bromophenyl)amminium cation [(p-BrC6H4)3N+] is described in detail.
Abstract: Stable triarylamminium salts may be used as convenient one-electron oxidants for a range of organic molecules. Synthesis and characterisation of perchlorate and hexachloroantimonate salts of the tris-(p-bromophenyl)amminium cation [(p-BrC6H4)3N+] are described in detail. The hexachloroantimonate is easier to prepare and is much the more stable, both thermally and photochemically.
91 citations
TL;DR: In this article, 1-Aminobenzotriazole is prepared in four steps from o-nitroaniline (54%) and, directly, by the amination of benzotrizole with hydroxylamine-O-sulphonic acid.
Abstract: 1-Aminobenzotriazole is prepared in four steps from o-nitroaniline (54%) and, directly, by the amination of benzotriazole with hydroxylamine-O-sulphonic acid. 2-Aminobenzotriazole is also formed in the latter reaction. Oxidation of 1-aminobenzotriazole with lead tetra-acetate, under very mild conditions, gives benzyne almost quantitatively which, in the absence of trapping agents, dimerises to biphenylene in unusually high yield. Trace amounts of triphenylene and 2-acetoxybiphenylene are also formed. Oxidation of 2-aminobenzotriazole with lead tetra-acetate or with iodobenzene diacetate gives cis,cis-mucononitrile in high yield.
77 citations
TL;DR: In this article, the ord curves of 40 carotenoids have been measured in dioxan, over the range 400-200 nm, in all cases a conjugated polyene system which is perturbed by one or two chiral end-groups.
Abstract: The ord curves of ca 40 carotenoids have been measured, chiefly in dioxan, over the range 400–200 nm The chromophore in all cases is a conjugated polyene system which is perturbed by one or two chiral end-groups The curves are analysed in terms of the simple additivity of the effects of end-groups, and the absolute configurations of several compounds have been provisionally assigned
55 citations
TL;DR: Fucoxanthin is an allenic carotenoid with a structure as 3′-acetoxy-5,6-epoxy-3,5′-dihydroxy-6′,7,8, 5′,6′-hexahydro-β-caroten-8-one.
Abstract: Fucoxanthin is an allenic carotenoid. Chemical and spectroscopic studies establish its structure as 3′-acetoxy-5,6-epoxy-3,5′-dihydroxy-6′,7′-didehydro-5,6,7,8,5′,6′-hexahydro-β-caroten-8-one (15).
55 citations
TL;DR: The root material of Derris robusta has yielded nine natural products whose structures have been determined mainly by physical methods in association with a few partial syntheses and degradations as mentioned in this paper.
Abstract: The root material of Derris robusta has yielded nine natural products whose structures have been determined mainly by physical methods in association with a few partial syntheses and degradations. Four of these have been shown to be new natural isoflavones: derrustone (II), derrubone (IIIa), robustone (VIa), and robustone methyl ether (VIb). The other five compounds are derivatives of the 3-aryl-4-hydroxycoumarin type, and include derrusnin (VIIb), robustic acid (IXa), robustic acid methyl ether (IXb), robustin (XIIa), and robustin methyl ether (XIIb). These 3-aryl-4-hydroxy(or methoxy)coumarins are variants upon the isoflavonoid theme. The pattern relating the structures of these co-occurring isoflavones and 3-aryl-4-oxycoumarins indicates that the biosyntheses of these two natural product types probably have many common features.
41 citations
TL;DR: In this paper, it was shown that vincoside is the precursor of representative indole alkaloids from the Corynanthe, Aspidosperma, and Iboga families in Vinca rosea.
Abstract: Tryptamine acts as a precursor of the indole alkaloids in Vinca rosea. Secologanin (1) condenses with tryptamine to yield vincoside (2) and isovincoside (5), the absolute configuration of these products is determined and their chemistry is explored. It is demonstrated by single- and double-labelling experiments that vincoside is the precursor of representative indole alkaloids from the Corynanthe, Aspidosperma, and Iboga families in Vinca rosea; isovincoside is not involved in these biosyntheses. Vinca rosea plants are shown to contain vincoside, isovincoside, and N-acetylvincoside by a combination of radiochemical dilution analysis and direct isolation. [5-3H]-Loganin fed to Vinca rosea is incorporated efficiently into vincoside and isovincoside.The steps are discussed by which vincoside is converted into the three types of indole alkaloids and it is proved that the side-chain unsaturation of vincoside is essential for operation of the later biosynthetic stages. The main Part OF This work has been briefly reported.2,3
41 citations
TL;DR: In this article, the location of the oxygen function at the meso-position is confirmed by ring synthesis, and by-products are observed, one of which is formulated as a dioxo-b-tetrahydroporphyrin.
Abstract: Treatment of octaethylporphyrin with hydrogen peroxide in concentrated sulphuric acid in the cold gives a monoxy-derivative: the earlier structures advanced for this type of compound are disproved, and this particular example is formulated as 2,3,7,8,12,13,18,18-octaethyl-17-oxochlorin. By-products are observed, one of which is formulated as a dioxo-b-tetrahydroporphyrin.Benzoyl peroxide reacts with octaethylporphyrin in 1,2,4-trichlorobenzene at 95° to give 5-benzoyloxy-octaethylporphyrin. Hydrolysis of this gives octaethyloxophlorin, aspects of the chemistry of which are discussed. The location of the oxygen function at the meso-position is confirmed by ring synthesis.
39 citations
TL;DR: In this article, a formal synthesis of (±)-lycoramine was presented, based on the reduction of 2-bromo-5-hydroxy-N-(4-hydroxyphenethyl)-4-methoxy-N-methylbenzamide (VIII) with ferricyanide.
Abstract: Oxidation of 2-bromo-5-hydroxy-N-(4-hydroxyphenethyl)-4-methoxy-N-methylbenzamide (VIII) with ferricyanide afforded the narwedine-type enone (X) in an excellent yield (40%). Reduction of (X) with lithium aluminium hydride gave (±)-galanthamine (II) and (±)-epigalanthamine (XXI) in yields of 50 and 40% respectively. Oxidation of (II) with manganese dioxide afforded (±)-narwedine (XIX) This work also constitutes a formal synthesis of (±)-lycoramine.
38 citations
TL;DR: A number of aldehyde arylhydrazones have been oxidised with lead tetra-acetate in methanol as mentioned in this paper, and they have been trapped with acrylonitrile, to form 1,3-diphenylpyrazole-5-carbonitrile together with a small quantity of the isomeric 4-caroline.
Abstract: A number of aldehyde arylhydrazones have been oxidised with lead tetra-acetate. In many cases diacylhydrazines, RCO·NH·NAcAr, can be isolated in good yield. With benzaldehyde phenylhydrazone, provided that precautions are taken to avoid autoxidation, α-phenylazobenzyl acetate can be isolated in up to 27% yield. Evidence has been obtained that this compound is not the main precursor of the diacyl derivative PhCO·NH·NAcPh or of further oxidation products, but that these arise via the nitrilimine PhC[graphic omitted]Ph; this 1,3-dipolar compound has been trapped with acrylonitrile, to form 1,3-diphenylpyrazole-5-carbonitrile together with a small quantity of the isomeric 4-carbonitrile. Analogous nitrilimines have been similarly trapped during the oxidation of the p-nitrophenylhydrazones of benzaldehyde, propionaldehyde, benzoin, and benzil. Oxidations with lead tetrabenzoate, and with lead tetra-acetate in methanol, have also been carried out; they lead to azo-dibenzoates and azo-dimethyl ethers, respectively, and benzaldehyde phenylhydrazone also forms an azo-benzoate.The acylhydrazones PhCH:N·NH·COR (R = Ph or NPh2) undergo oxidative cyclisation with lead tetra-acetate to give high yields of the corresponding oxadiazoles. Likewise, the phenyl- and p-nitrophenyl-hydrazones of o-nitrobenzaldehyde are cyclised to 3-arylazoanthranil 1-oxides. Nitrilimines, by implication, mediate in each case.
TL;DR: The structures of cytochalasins C and D, metabolites of Metarrhizium anisopliae, have been determined in this paper, and the structures of these metabolites have been shown to be stable.
Abstract: The structures of cytochalasins C and D, metabolites of Metarrhizium anisopliae, have been determined.
TL;DR: In this paper, the order of reducing reactivity of a series of tervalent phosphorus reagents towards 2-nitrobiphenyl is (EtO)2N)3P ∼(EtN)2PMe ∼(NEt2N), (NEt 2 )2 > (PriO(3P ⋙ PCl3(inactive).
Abstract: Reduction of 2′,4′,6′-trimethyl-2-nitrobiphenyl by triethyl phosphite gives 2-amino-2′,4′,6′-trimethylbiphenyl and triethyl N-(2′,4′,6′-trimethylbiphenyl-2-yl)phosphorimidate. The same reduction, carried out in cumene or in t-butylbenzene gives, additionally, 8,10-dimethylphenanthridine, and, in cumene, 2,3-dimethyl-2,3-diphenyl-butane, indicating the intermediacy of a triplet nitrene. Reduction of nitrobenzene by diethyl methylphosphonite in an excess of diethylamine gives 2-diethylamino-3H-azepine (83%), while the corresponding reaction with 2-nitrobiphenyl gives 2-diethylamino-3-phenyl-3H-azepine (13%) in addition to carbazole (63%), pointing to an intermediate similar to that present in decompositions of azides, i.e. a nitrene or nitrenoid species, the nature of which is discussed.The order of reducing reactivity of a series of tervalent phosphorus reagents towards 2-nitrobiphenyl is (EtO)2PMe (Et2N)3P ∼(EtO)P(NEt2)2 > (EtO)3P ∼(PriO)3P ⋙ PCl3(inactive).
TL;DR: In this article, the preparation of secologanin (V) was described and this product was used for the partial synthesis of desacetylipecoside (XX) and of ipecoside(XXI).
Abstract: The preparation of secologanin (V) is described and this product is used for the partial synthesis of desacetylipecoside (XX) and of ipecoside (XXI). The isomers (XXIII) and (XXIV) were also obtained. Tracer experiments on Vinca rosea plants establish that secologanin is a specific precursor of representative indole alkaloids from the Corynanthe, Aspidosperma, and Iboga families. The further requirement for a true precursor, that its presence in the living system should be demonstrated, is met by isolation of secologanin from Vinca rosea plants both by radiochemical dilution analysis and by macro-isolation. The biosynthesis of secologanin from loganin is established in Vinca rosea and Menyanthes trifoliata plants. A preliminary account of this work has been published.2
TL;DR: Bi-functional catalysts such as 2-hydroxypyridine are shown to be valuable in promoting the reaction between a variety of aliphatic amines and non-activated esters to give substituted amides; they are less effective with aniline.
Abstract: Bi-functional catalysts such as 2-hydroxypyridine are shown to be valuable in promoting the reaction between a variety of aliphatic amines and non-activated esters to give substituted amides; they are less effective with aniline. This method has been applied to the synthesis of the emetine intermediate, an N-substituted benzo[a] quinolizineacetamide (II), and analogues.
TL;DR: The addition of methanide to arenecyclopentadienyliron cations is subject in most cases to the same directive influences as for the hydride addition studied previously.
Abstract: The addition of methanide to arenecyclopentadienyliron cations is shown to be subject in most cases to the same directive influences as for the hydride addition studied previously. However, hexamethylbenzenecyclopenta-dienyliron cation undergoes addition at the cyclopentadienyl ring giving a neutral complex, which was identified by conversion into hexamethylbenzenemethylcyclopentadienyliron cation, a rare example of endo-hydride abstraction. Extensive spectroscopic correlations strengthen previous of the highly stereospecific exo-direction of such addition reactions and of exo-hydride removal from the cyclohexadienyl products.
TL;DR: On treatment with boron trifluoride-diethyl ether in benzene solution, tri-O-acetyl-D-glucal dimerises as discussed by the authors.
Abstract: On treatment with boron trifluoride–diethyl ether in benzene solution, tri-O-acetyl-D-glucal dimerises, and from the products the crystalline C–C linked disaccharide derivative 1,3,4,6-tetra-O-acetyl-2-C-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranosyl)-2-deoxy-β-D-glucopyranose has been isolated. Dimerisation is believed to occur by the trans-addition of one molecule of 1,4,6-tri-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranose to the double bond of another, and in agreement with this, evidence has been obtained that tri-O-acetyl-D-glucal initially rearranges in the presence of the catalyst (or thermally) to give mainly the 2,3-unsaturated isomer.
TL;DR: In this article, it was shown that aryl halides can be diverted to nucleophilic sustitution (ArHal → ArOAlk) by operating with a substantially homogeneous liquid medium containing copper(I) salts as catalysts.
Abstract: Whereas sodium alkoxides reduced aryl halides (ArHal → ArH) under heterogeneous catalytic conditions, e.g., in solutions containing a suspension of copper(I) oxide, reaction could in some cases be diverted to nucleophilic sustitution (ArHal → ArOAlk) by operating with a substantially homogeneous liquid medium containing copper(I) salts as catalysts. In a suitably chosen reaction system, e.g., ArHal–NaOAlk–AlkOH–Cul–2,4,6-collidine, at ∼100–120°, high yields of ethers resulted with alkoxides derived from normal monohydric alkanols, but reduction usually predominated with alkoxides from other types of alcohols. The process is exemplified by preparations of methyl or ethyl ethers (∼80–100%) from monocyclic or polycyclic aryl bromides or iodides, including those containing Me, OMe, or CO2H groups as nuclear substituents. Lower yields (∼35–50%) resulted when OH or NH2 were substituents, probably because of their participation in competing reactions, and no ethers were obtained when NO2,CHO, or COMe were substituents.
TL;DR: The Schmidt reaction with benzocyclobutenones and 1-indanones is strongly affected by substituents in the aromatic ring in positions para or ortho to the carbonyl group.
Abstract: Eighteen 1-indanones, fifteen 1-tetralones, two 1-benzosuberanones, and two benzocyclobutenones, as well as four acetophenones, have been submitted to the Schmidt reaction in sulphuric acid, polyphosphoric acid, or molten trichloroacetic acid, and the ratios of the respective isomeric rearrangement products have been determined. The direction of the rearrangement in the Schmidt reaction with benzocyclobutenones and 1-indanones is strongly affected by the substituents in the aromatic ring in positions para or ortho to the carbonyl group, and by the acid medium used in the reaction. The same influence was observed to a lesser extent, but still markedly, with 1-tetralones. In ketones having a flexible structure, such as 1-benzosuberanones and acetophenones, no appreciable influence of substituents and acid mediums was noted on the direction of migration, giving in all cases predominantly N-aryl amide.
TL;DR: In this article, 1-Chlorobenzotriazole is converted by sodium hypochlorite into its stable, crystalline 1-chloroderivative, the chemistry of which is dominated by the positive-halogen character of the chlorine atom.
Abstract: Benzotriazole is rapidly and quantitatively converted by sodium hypochlorite into its stable, crystalline 1-chloroderivative, the chemistry of which is dominated by the positive-halogen character of the chlorine atom.1-Chlorobenzotriazole has considerable potential as an oxidant; it oxidises alcohols to carbonyl compounds, hydrazo- to azo-compounds, and 1,1-disubstituted hydrazines, all in high yield under very mild conditions.1-Chlorobenzotriazole reacts with diethyl ether to give 1-(1-ethoxyethyl)benzotriazole; the same product was formed, unexpectedly, by treatment of benzotriazole in ether with chloramine or nitrosyl chloride.Radical chain mechanisms are proposed for these oxidation and substitution reactions.
TL;DR: In this paper, an improved and direct method for the preparation of 5-substituted 2-aminobenzenethiols (III, R = Cl, Br, Me, OMe, or NO2) through hydrolytic cleavage of substituted 2aminobenzothiazoles (II, R.
Abstract: An improved and direct method for the preparation of 5-substituted 2-aminobenzenethiols (III; R = Cl, Br, Me, OMe, or NO2) through hydrolytic cleavage of substituted 2-aminobenzothiazoles (II; R = Cl, Br, Me, OMe, or NO2) without the necessity for isolating the zinc thiolate intermediate is reported. Some 3-mono- and 3,7-di-substituted phenothiazines have been prepared from these thiols via formation of aryl sulphides and Smiles rearrangement. Some limitations of the Smiles rearrangement under alkaline conditions are discussed. Structures are supported by i.r. and u.v. spectral studies.
TL;DR: The first isomerization of an indol-2-yl 1,2,5,6-tetrahydro-4-pyridyl ketone to a cyclic enamine was described in this article.
Abstract: The syntheses of the racemic forms of the indole alkaloids dasycarpidone (2b), 3-epi-dasycarpidone (2c), uleine (2a), and 3-epi-uleine (2d) together with that of 3-de-ethyldascarpidone (2e) are described. The key step in the approach involved the isomerisation of an indol-2-yl 1,2,5,6-tetrahydro-4-pyridyl ketone to an indol-2-yl 1,4,5,6-tetrahydro-4-pyridyl ketone (not isolated). This in turn in reacting as a cyclic enamine provided, by protonation an electrophilic centre for eventual closure to the indole β-position.
TL;DR: Two crystalline pigments, aeruginosins A and B have been isolated from a red strain of Ps.
Abstract: Two crystalline pigments, aeruginosins A and B have been isolated from a red strain of Ps. aeruginosa. Aeruginosin A is shown to be the inner salt of 2-amino-6-carboxy-10-methylphenazinium hydroxide.
TL;DR: Samples of lutein (XI), and of zeaxanthin (III) from various natural sources have been compared and their structures have been confirmed as mentioned in this paper, showing that the latter has the allenic structure 5,6-epoxy-3,3′,5′-trihydroxy-6′,7′-didehydro-5,6, 5′,6′-tetrahydro-β-carotene (IVa).
Abstract: Neoxanthin, a universal pigment in green leaves, has been shown to have the allenic structure 5,6-epoxy-3,3′,5′-trihydroxy-6′,7′-didehydro-5,6,5′,6′-tetrahydro-β-carotene (IVa).Samples of lutein (XI), and of zeaxanthin (III), from various natural sources have been compared and their structures have been confirmed.Attempts to isolate taraxanthin, which Curl has suggested may be identical with neoxanthin, yielded the well known epoxide (XIV) of lutein but no carotenoid possessing the O4 formulation proposed for taraxanthin.
TL;DR: Two new members of the rare isoflavan series and two new pterocarpans have been isolated from Lonchocarpus laxiflorus as discussed by the authors, and physical methods involved in solving the structural problems associated with the penta-substituted ring B of three of these compounds include the study of methoxy-proton shifts and i.m.d.
Abstract: Two new members of the rare isoflavan series and two new pterocarpans have been isolated from Lonchocarpus laxiflorus. Physical methods involved in solving the structural problems associated with the penta-substituted ring B of three of these compounds include the study of methoxy-proton shifts and i.r. stretching frequencies. Some possible errors of the method of methoxy-proton shifts are pointed out. Steric factors result in one isoflavan (Ionchocarpan) and its derivatives taking up unusual conformations; this gives rise to misleading o.r.d. curves and is also reflected in the n.m.r. spectra.
TL;DR: The constitutions of the pigments produced by moulds of the genus Elsinoe, the elsinochromes A, B, and C, have been elucidated in this article.
Abstract: The constitutions of the pigments produced by moulds of the genus Elsinoe, the elsinochromes A, B, and C, have been elucidated. The stereochemistry of elsinochrome A has been established.
TL;DR: In this paper, it was shown that when the epoxides are treated with dilute sulphuric acid in the presence of ethanol, monoethers of acetylenic diols are formed.
Abstract: Acetylenic αβ-epoxides react with dilute sulphuric acid and mercuric sulphate on heating to give furans in good yields; the reaction involves an internal hydration at a terminal acetylenic carbon atom. Under the influence of sulphuric acid alone, only small quantities of furans are formed; the major products are acetylenic diols. These have been shown to be probable intermediates in the formation of the furans. When the epoxides are treated with dilute sulphuric acid in the presence of ethanol, monoethers of acetylenic diols are formed. Acetylenic βγ-epoxides have also been shown to give furans in the mercuric sulphate-catalysed reaction with sulphuric acid.
TL;DR: In this paper, the preparation and properties of dihydrobromides of some 4-picolyl esters of amino-acids (I), and of their benzyloxycarbonyl derivatives, are described.
Abstract: The preparation and properties of the dihydrobromides of some 4-picolyl esters of amino-acids (I), and of their benzyloxycarbonyl derivatives, are described. The esters may be cleaved by cold alkali, by catalytic hydrogenation, by sodium in liquid ammonia, and by electrolytic reduction. A new procedure for the facilitation of peptide synthesis is reported, in which the carboxy-terminal residue is incorporated as its 4-picolyl ester; after each coupling reaction the product is separated from the excess of acylating agent, co-products, and by-products by extraction into an acidic phase, e.g. sulphoethyl-Sephadex. The procedure is illustrated by two syntheses of L-leucyl-L-alanylglycyl-L-valine.
TL;DR: Anacyclus pyrethrum D.C. as discussed by the authors contains N-(2′-p-hydroxyphenylethyl) deca-, dodeca-, and tetradeca-trans-2, trans-4-dienamide, a new series of tyramine amides corresponding to isobutylamides which this plant produces.
Abstract: Anacyclus pyrethrum D.C. (Compositae) contains N-(2′-p-hydroxyphenylethyl) deca-, dodeca-, and tetradeca-trans-2, trans-4-dienamide, a new series of tyramine amides corresponding to isobutylamides which this plant produces. The tyramides, and the corresponding isobutylamides, are synthesised stereospecifically by phosphonatenaion synthesis. Anacyclus pyrethrum is found to contain the lignan (+)-sesamin and attention is drawn to the cooccurrence of lipid (and other) amides with lignans in a number of plants from three families (Compositae, Piperaceae, and Rutaceae).
TL;DR: Three pigments from sea urchins have been identified as fucoxanthin (II), fucox anthinol (I), and a novel allenic ketone (V), "paracentrone".
Abstract: Three pigments from sea urchins have been identified as fucoxanthin (II), fucoxanthinol (I), and a novel allenic ketone (V), ‘paracentrone.’