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Showing papers in "Journal of The Chemical Society C: Organic in 1971"


Journal ArticleDOI
TL;DR: A plant-growth inhibitor produced by Lasiodiplodia theobromae has been shown to be jasmonic acid (Ia) and six other new fungal metabolites have been isolated from L:theobromai.
Abstract: A plant-growth inhibitor produced by Lasiodiplodia theobromae has been shown to be jasmonic acid (Ia). Six other new fungal metabolites have been isolated from L:theobromae—lasiodiplodin (Va), de-O-methyl-lasiodiplodin (Vb), cis-4-hydroxymellein (XIIIa), indole-3-carboxylic acid, 3-formylindole, and ethyl hydrogen fumarate. (–)-Mellein (XIIIb) is also produced.

223 citations


Journal ArticleDOI
TL;DR: In this paper, the preparation of 21-oxa, 21-thia-, 21,23-dioxa-, 21-23dithia-, and 21oxa-23-thia-porphins is described.
Abstract: The preparation of 21-oxa, 21-thia-, 21,23-dioxa-, 21,23-dithia-, and 21-oxa-23-thia-porphins is described. These new porphin analogues have spectral properties similar to those of the porphins, which supports their formulation as aromtic macrocycles. Surprising basicity is displayed by 21,22- and 21,23-dioxaporphins and unusual mass spectra are produced by the oxaporphins. Only the 21-oxa- and 21-thia-porphins form metal complexes under the usual conditions used for metalloporphin formation. The results of deuterium exchange studies on the new macrocycles are reported.

65 citations


Journal ArticleDOI
TL;DR: In this article, eight new steroidal lactones of the withanolide series have been isolated from the leaves of Withania somnifera (Solanaceae) growing in North-Western India.
Abstract: Eight new steroidal lactones of the withanolide series have been isolated from the leaves of Withania somnifera(Solanaceae) growing in North-Western India. This population of W. somnifera differs from those investigated so far and constitutes a new chemotype. The new compounds (IV)—(XI) have been investigated by chemical degradation and interconversion reactions, as well as by analysis of their spectral properties. The following structures have been assigned: 5α,17α-dihydroxy-1-oxo-6α,7α-epoxy-22R-witha-2,24-dienolide (IV); 5α,17α-dihydroxy-1-oxo-22R-witha-2,6,24-trienolide (V); 5α,27-dihydroxy-1-oxo-6α,7α-epoxy-22R-witha-2,24-dienolide (VIa); 4β,17α-dihydroxy-1-oxo-5β,6β-epoxy-22R-witha-2,24-dienolide (VIIa); 17α,27-dihydroxy-1-oxo-22R-witha-2,5,24-trienolide (VIIIa); 7α,27-dihydroxy-1-oxo-22R-witha-2,5,24-trienolide (VIIIa); 7α,27-dihydroxyl-1-oxo-22R-witha-2,5,24-trienolide (IXa); 1α,3β,5α-trihydroxy-6α,7α-epoxy-22R-with-24-enolide (Xa); 4β-hydroxy-5β,6β-epoxy-1-oxo-22R-witha-2,14,24-trienolide (XIa).

65 citations


Journal ArticleDOI
TL;DR: The chemical and spectroscopic characteristics of bikaverin and norbkaverin, two hydroxy-quinonoid benzoxanthones isolated from Gibberella fujikuroi and other Fusarium spp.
Abstract: The chemical and spectroscopic characteristics of bikaverin and norbikaverin, two hydroxy-quinonoid benzoxanthones isolated from Gibberella fujikuroi and other Fusarium spp., are fully consistent with the established structures. Bikaverin forms two series of isomeric O-alkyl and O-acyl derivatives corresponding to tautomeric forms of the parent hydroxy-quinone; the related problem of proton location in the hydroxy-quinones, and in naphthazirins generally, is discussed in the light of n.m.r. data.

65 citations


Journal ArticleDOI
TL;DR: The use of nitrones and nitroso-compounds as spin traps is complicated by the ease with which they react with anions to give amino-oxy-anions which are invariably oxidised to some extent to nitroxides as mentioned in this paper.
Abstract: Use of nitrones and nitroso-compounds as spin traps is complicated by the ease with which they react with anions to give amino-oxy-anions which are invariably oxidised to some extent to nitroxides. Several polymeric nitroxides have been prepared in this way.

56 citations


Journal ArticleDOI
TL;DR: The n.m.v.r. spectra of xanthine and its 1-methyl derivative suggests that their monoanions are tautomeric mixtures in which both the N (3) H and N (7) H groups participate in ionisation as mentioned in this paper.
Abstract: The n.m.r. chemical shifts of the 8-protons in xanthines with an unsubstituted imidazole ring (class a) and in 7-methylxanthines (class b) are very similar; however the 8-H signals for 9-methyl derivatives (class c) occur at higher field. Thus, in aqueous solution, members of class a must be essentially present as the N(7) H tautomers.Methyl substituents in various positions may be distinguished by their n.m.r. signals; their δ values can be arranged in the following order: 7- > 9- > 3- > 1-methyl. The signals of individual N-methyl groups are influenced only slightly by introduction of additional alkyl substituents, with the exception of 3,9-dimethylxanthines, in the spectra of which both methyl signals are shifted to lower field because of steric interference.U.v. spectra establish the order of anion formation in 7- and 9-methylxanthine as 3 → 1 and in 3-methylxanthine as 7 → 1. However, the displacement of the 8-H signals in the n.m.r. spectra of xanthine and its 1-methyl derivative suggests that their monoanions are tautomeric mixtures in which both the N (3) H and N (7) H groups participate in ionisation.Cation formation is accompanied by a much larger displacement of the 8-H n.m.r. signal in class c than in class a or b.

56 citations


Journal ArticleDOI
TL;DR: In this article, 1233A is shown to be 12-hydroxy-13-hydroxymethyl-3,5,7-trimethyltetradeca-2,4-dienedioic acid 12,14-lactone.
Abstract: Antibiotic 1233A is shown to be 12-hydroxy-13-hydroxymethyl-3,5,7-trimethyltetradeca-2,4-dienedioic acid 12,14-lactone (1a). A second metabolite, 1233B, is believed to be one of the C-12 epimers of the parent acid (5a).

44 citations


Journal ArticleDOI
TL;DR: A factor producing morphological changes, normally indicative of senescence, in fungal cultures was isolated from aged cultures of Fusarium oxysporum, and later from cultures of f. lycopersici as mentioned in this paper.
Abstract: A factor producing morphological changes, normally indicative of senescence, in fungal cultures was isolated from aged cultures of Fusarium oxysporum, and later from cultures of Fusarium oxysporum f. sp. lycopersici. It is a red crystalline substance C20H14O8 and has been shown by direct comparison to be identical with ‘bikaverin’ from Fusarium moniliforme(=Gibberella fujikuroi) and from another Fusarium species. The structure, 7,10-dihydro-6,11-dihydroxy-3,8-dimethoxy-1-methyl-12H-benzo[b]xanthene-7,10,12-trione, has been proved elsewhere by X-ray crystallography. The substance may be identical with a pigment named lycopersin and reported under a different formula.

41 citations


Journal ArticleDOI
TL;DR: The structure of the fungal metabolite monascin has been unequivocally defined: the relative stereochemistry of the azaphilones has been deduced.
Abstract: The structure of the fungal metabolite monascin has been unequivocally defined: the relative stereochemistry of the azaphilones has been deduced

40 citations


Journal ArticleDOI
TL;DR: In this article, the biogenetic significance of co-occurrence of these compounds is discussed and syntheses of hydrocotoin, methylhydrocotoins, and 2,3,6,7-tetramethoxyxanthone are described.
Abstract: Ten metabolites, hydrocotoin (2-hydroxy-4,6-dimethoxybenzophenone), 2,3′-dihydroxy-4,6-dimethoxybenzophenone, 1,3,5-trihydroxyxanthone, 4′,5′-dihydro-1,6,7-trihydroxy-4′,4′,5′-trimethylfurano(2′,3′ : 3,4)xanthone, volkensiflavone, morelloflavone; and from methylation of the crude extracts, 1,7-dimethoxyxanthone, 1-hydroxy-5-methoxyxanthone, 1-hydroxy-3,7-dimethoxy-2-(3,3-dimethylallyl)xanthone, and 1,3,6,7-tetramethoxyxanthone have been isolated from the heartwood of Allanblackia floribunda Oliver. The biogenetic significance of the co-occurrence of these compounds is discussed and syntheses of hydrocotoin, methylhydrocotoin, and 2,3′,4,6-tetramethoxybenzophenone are described.

37 citations


Journal ArticleDOI
TL;DR: The Diels-Alder adduct between ergosterol and 4-phenyl-1,2,4-triazolin-3,5-dione was used in a synthesis of ergosta-5,7,22,24(28)-tetraen-3β-ol.
Abstract: The Diels–Alder adduct between ergosterol and 4-phenyl-1,2,4-triazolin-3,5-dione is reconverted into ergosterol in high yield by reduction with lithium aluminium hydride. The adduct has been used in a synthesis of ergosta-5,7,22,24(28)-tetraen-3β-ol. An analogous synthesis of ergosta-5,7,22,24(28)-tetraen-3β-ol using radioactive intermediates enabled the intermediacy of this compound in ergosterol biosynthesis in yeast to be demonstrated.

Journal ArticleDOI
TL;DR: Gangetin, a new pterocarpan from Desmodium gangeticum, has been assigned the structure (1) on the basis of chemical and spectroscopic evidence as mentioned in this paper.
Abstract: Gangetin, a new pterocarpan from Desmodium gangeticum, has been assigned the structure (1) on the basis of chemical and spectroscopic evidence.

Journal ArticleDOI
TL;DR: The Dragon's blood resin has yielded six new natural substances, (2S)-5-methoxy-6-methylflavan-7-ol (1) and (2R)-flavan-1-ol as mentioned in this paper, which have been determined by physical methods and chemical interconversions.
Abstract: Dragon's blood resin has yielded six new natural substances, (2S)-5-methoxy-6-methylflavan-7-ol (1), (2S)-5-methoxyflavan-7-ol (2), the quinone methides nordracorhodin (6) and nordracorubin (10), 2,4-dihydroxy-5-methyl-6-methoxychalcone (7), and 2,4-dihydroxy-6-methoxychalcone (8). Their structures have been determined by physical methods and chemical interconversions. The absolute 2S configuration for flavans (1) and (2) has been established by comparison of c.d. data with those for synthetic (2R)-flavan-7-ol (14).

Journal ArticleDOI
TL;DR: In this paper, 2,6-Di-t-butyl-4-alkylphenols undergo anodic hydroxylation giving high yields of the corresponding 4-hydroxy-cyclohexa-2,5-dienones providing that the medium is buffered to avoid acid-catalysed dealkylation and quinone formation.
Abstract: 2,6-Di-t-butyl-4-alkylphenols undergo anodic hydroxylation giving high yields of the corresponding 4-hydroxy-cyclohexa-2,5-dienones providing that the medium is buffered to avoid acid-catalysed dealkylation and quinone formation. The use of nucleophiles other than water affords a general synthesis of 4-substituted cyclohexa-2,5-dienones.

Journal ArticleDOI
TL;DR: In this paper, four 4n-propyl-, one 4-n-pentyl-, and four 4-phenyl-coumarins have been isolated from the bark of Mammea africana G. Don and identified.
Abstract: Four 4-n-propyl-, one 4-n-pentyl-, and four 4-phenyl-coumarins have been isolated from the bark of Mammea africana G. Don and identified. All are derived from 5,7-dioxygenated coumarins, and eight of the structures contain an isoprene unit and an acyl side chain at either C-6 or C-8. In four cases the isoprene unit exists as a 3-methylbut-2-enyl side chain but otherwise it forms part of a chromen or benzofuran system. The metabolites are 5,7-dihydroxy-6-(3-methylbut-2-enyl)-8-(2-methylbutyryl)-4-n-propylcoumarin (1)(mammea B/BB) 5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(3-methylbutyryl)-4-phenylcoumarin (5)(mammeisin, mammea A/AA) 5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(2-methylbutyryl)-4-phenylcoumarin (7)(mammea A/AB, MAB 1), 5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(2-methylbutyryl)-4-n-propylcoumarin (8)(MAB 2), 4′,5′-dihydro-5-hydroxy-5′-(1-hydroxy-1-methylethyl)-6-(2-methylbutyryl)-4-phenylfuro[2′,3′ : 7,8]coumarin (9)(MAB 3), 4′,5′-dihydro-5-hydroxy-5′-(1-hydroxy-1-methylethyl)-6-(2-methylbutyryl)-4-n-propylfuro[2′,3′ : 7,8]coumarin (10)(MAB 4), 5-hydroxy-6′,6′-dimethyl-6-(2-methylbutyryl)-4-phenylpyrano[2′,3′ : 7,8]coumarin (11)(MAB 5), 5-hydroxy-6′,6′-dimethyl-6-(2-methylbutyryl)-4-n-propylpyrano[2′,3′ : 7,8]coumarin (12)(MAB 6) and 5,7-dihydroxy-8-(2-methylbutyryl)-4-n-pentylcoumarin (13). The structures of the pyranocoumarins have been confirmed by partial synthesis. The possible biogenetic relationship between the coumarins and xanthones in Guttiferae is discussed.

Journal ArticleDOI
TL;DR: In this paper, X-ray analysis of the meta-bridged biphenyl, 16-bromomyricanol (nitromethane solvate), by the heavy-atom method, confirmed these assignments, and gave the absolute configuration of myricanol.
Abstract: Chemical and spectroscopic studies lead to the [7,0]metacyclophane structures (2) and (3) for myricanol and myricanone, phenolic extractives from Myrica nagi. X-Ray analysis of the meta-bridged biphenyl, 16-bromomyricanol (nitromethane solvate), by the heavy-atom method, confirmed these assignments, and gave the absolute configuration of myricanol. The compound crystallises in the monoclinic space group P21 with Z= 2 in a unit cell of dimensions a= 6·02, ± 0·01, b= 17·34 ± 0·02, c= 11·22 ± 0·02 A, and β= 98·4°± 0·2°; the structure was refined to R 0·057 for 1075 independent reflections. C.d. measurements suggest that myricanol prefers the same conformation in solution as in the crystalline state. The biphenyl nucleus in 16-bromomyricanol is deformed by meta,meta-bridging. Similar strain in myricanone (3) is relieved by rearrangement with Lewis acids to the ortho,meta-bridged ketone (13). The natural phenols may be biogenetically related to diarylheptanoids.

Journal ArticleDOI
TL;DR: The linear structure for the ergot pigment, ergochrysin A, has been confirmed by n.r.m. spectroscopy and by chemical degradation, and it has been established that the linkage between the two halves of the secalonic acids A, B, C, and D is 2,2′- and not 4,4′- as previously suggested.
Abstract: The linear structure for the ergot pigment, ergochrysin A, has been confirmed; isoergochrysin A has the corresponding angular structure. The synthesis of various relevant biphenyls, including 3-acetyl-4-hydroxy-2,2′,4′-trimethoxybiphenyl, 3,3′-diacetyl-4,4′-dihydroxy-2,2′-dimethoxybiphenyl, and derivatives is described. Iodination of 2′-hydroxy-6′-methoxyacetophenone gives 2′-hydroxy-3′-iodo-6′-methoxyacetophenone and not 2′-hydroxy-5′-iodo-6′-methoxyacetophenone as previously claimed. Similarly the compounds previously described as 8-iodo-5-methoxy-2-methylchromone and 8,8′-bis-(5-methoxy-2-methylchromone) are 6-iodo-5-methoxy-2-methylchromone and 6,6′-bis-(5-methoxy-2-methylchromone), respectively.By n.m.r. spectroscopy and by chemical degradation it has been established that the linkage between the two halves of the secalonic acids A, B, C, and D is 2,2′- and not 4,4′- as previously suggested. The 2,2′-linkage is also present in ergoxanthin and ergochrysin B.Ullmann condensation of 5-O-benzoyl-2-iodo-1,9-di-O-methylhemiergoflavin gave 5,5′-di-O-benzoyl-1,1′,9,9′-tetra-O-methylergoflavin, which on demethylation and debenzoylation gave ergoflavin, thereby constituting a partial synthesis of this metabolite.

Journal ArticleDOI
TL;DR: In this article, five new compounds isolated from the heartwood of Combretum apiculatum have been shown by chemical and spectroscopic methods, supported by synthesis, to be 4,7-dihydroxy-2,6-dimethoxy-, 4, 7-dioxyphenanthrene -2,3, 6-trimethoxy, and 2.6-doxy-3, 4,4, 7,7, trimethoxide-9,10-dimethylhexanthrene.
Abstract: Five new compounds isolated from the heartwood of Combretum apiculatum have been shown by chemical and spectroscopic methods, supported by synthesis, to be 4,7-dihydroxy-2,6-dimethoxy-, 4,7-dihydroxy-2,3,6-trimethoxy-, and 2,6-dihydroxy-3,4,7-trimethoxy-9,10-dihydrophenanthrene, and 2,6-dihydroxy-3,4,7-trimethoxy- and 4,6,7-trihydroxy-2,3-dimethoxyphenanthrene.

Journal ArticleDOI
TL;DR: In this article, the benzophenone-sensitised photo-oxidation of primary, secondary, and tertiary aliphatic amines and N-alkylanilines was investigated.
Abstract: Product studies are reported on the benzophenone-sensitised photo-oxidation of primary, secondary, and tertiary aliphatic amines and N-alkylanilines. Aliphatic amines gave aldehydes and imines, whereas N-alkylanilines were dealkylated but did not give imines. Amines which are known physical quenchers of singlet oxygen were efficiently oxidised. The reactivity of these compounds, and the type of products formed in the reaction, are explainable in terms of a mechanism in which hydrogen atom abstraction from the amine by triplet ketone is the primary chemical reaction. The results are not in accord with the participation of singlet oxygen. Quantum yield measurements of oxygen uptake, amine disappearance, and product formation are consistent with the proposed mechanism.

Journal ArticleDOI
TL;DR: In this article, a new C9H12O3 compound, 2,3-dihydro-2-hydroxy-2,4-dimethyl-5-transpropenylfuran-3-one, has been isolated in low yield from culture filtrates of the phytopathogenic fungus Stemphylium radicinum, C.I.M. 105654, in addition to Radicinin and pyrenophorin which were obtained previously.
Abstract: Pyrenophorol, dehydrocurvularin, and a new C9H12O3 compound, shown to be 2,3-dihydro-2-hydroxy-2,4-dimethyl-5-trans-propenylfuran-3-one, have been isolated in low yield from culture filtrates of the phytopathogenic fungus Stemphylium radicinum, C.M.I. 105654, in addition to radicinin and pyrenophorin which were obtained previously. The pyrenophorin was sometimes accompanied by an isomeric compound, possibly an artifact derived from it by an intramolecular Michael condensation.

Journal ArticleDOI
TL;DR: In this paper, a simple method for monobromination of aromatic amines predominantly or exclusively in the para-position is reported, and yields are generally higher than 90% when protection of the amino-group is not necessary.
Abstract: A simple method for monobromination of aromatic amines predominantly or exclusively in the para-position is reported. 2,4,4,6-Tetrabromocyclohexa-2,5-dienone is used as the halogenating agent in dichloromethane or chloroform. Protection of the amino-group is not necessary and yields are generally higher than 90%.

Journal ArticleDOI
TL;DR: Monamycin, a crystalline antibacterial preparation isolated from cultures of Streptomyces jamaicensis, consists of a mixture of fifteen cyclohexadepsipeptides, six of which contain chlorine.
Abstract: Monamycin, a crystalline antibacterial preparation isolated from cultures of Streptomyces jamaicensis, consists of a mixture of fifteen cyclohexadepsipeptides, six of which contain chlorine. Each molecular species consists of one residue of α-hydroxy-acid (either L-2-hydroxy-3-methylbutanoic acid or L-2-hydroxy-3-methylpentanoic acid) and five residues of α-amino-or imino-acid. The latter consist of N-methyl-D-leucine, L-proline (or trans-4-methyl L-proline), D-isoleucine (or D-valine), (3R)-piperazic acid [or (3R,5S)-5-chloropiperazic acid, or (3R)-4,5 (or 5,6)-dehydropiperazic acid], and (3S,5S)-5-hydroxypiperazic acid. The name piperazic acid is assigned to hexahydropyridazine-3-carboxylic acid.

Journal ArticleDOI
TL;DR: Evidence is presented that 2-Pyridyl esters are likely to be particularly useful in solid-phase peptide synthesis, and in the synthesis of O-peptides and depsipeptides.
Abstract: 2-Pyridyl esters of N-acyl-amino-acids may be prepared from the acids, 2-hydroxypyridine, and NN′-dicyclohexylcarbodi-imide in pyridine (only N-acylureas are formed in acetonitrile or dichoromethane). The N-t-butoxy-carbonyl-amino-acid 2-pyridyl esters are mostly crystalline, stable, and in non-polar solvents considerably more reactive towards nucleophiles (amines, amino-acid esters and amides, hindered amino-acid derivatives, and hydroxy-compounds) than the corresponding p-nitrophenyl esters. Evidence is presented that they are likely to be particularly useful in solid-phase peptide synthesis, and in the synthesis of O-peptides and depsipeptides.

Journal ArticleDOI
TL;DR: In this article, the (±)-3-hydroxy-β-ionone has been prepared and converted into zeaxanthin, β-cryptoxanthin and zeinoxanthins.
Abstract: (±)-3-Hydroxy-β-ionone has been prepared and converted into zeaxanthin, β-cryptoxanthin, and zeinoxanthin (α-cryptoxanthin).

Journal ArticleDOI
TL;DR: The purpurosamines are shown to be members of the 2,6diamino-2,3,4,6-tetradeoxyhexose family, a new class of naturally occurring monosaccharides.
Abstract: Separation of the gentamicin C components by column chromatography and subsequent mercaptolysis of their per-N-acetyl derivatives has permitted the isolation of derivatives of three new amino-sugars named purpurosamine A, B and C corresponding to gentamicins C1, C2a, and C1a respectively. The purpurosamines are shown to be members of the 2,6-diamino-2,3,4,6-tetradeoxyhexose family, a new class of naturally occurring monosaccharides.

Journal ArticleDOI
TL;DR: The absolute stereochemistry of the 2-deoxystreptamine portion of these tetra-N-acetates was determined by a circular dichroism method in this paper.
Abstract: Methanolysis of the gentamicin C components gave methyl garosaminide and the corresponding gentamines, isolated as crystalline tetra-N-acetates. The absolute stereochemistry of the 2-deoxystreptamine portion of these tetra-N-acetates was determined by a circular dichroism method. Methylation of the penta-N-acetylgentamicin C components followed by acid hydrolysis and reacetylation gave, in each case, NN′-diacetyl-2-deoxy-NN′,5-O-tri-methylstreptamine, establishing the gentamicins to be 4,6-disubstituted 2-deoxystreptamine derivatives.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the temperature at which the n.m.r. coupling between tin atoms and the alkoxy-groups is broken in the alkoxides Bu3SnOR′ shows that the rate of exchange follows the sequence MeO > EtO > PhCH2·O > Me3C·CH2 ·O, Me2CH·O, PhMeCH ·O.
Abstract: Trialkyltin alkoxides, R3SnOR′, can be prepared conveniently by thermal decarboxylation of a mixture of the oxide, (R3Sn)2O, and dialkyl carbonate, (R′O)2CO, or (except when R = Me or Et) by azeotropic dehydration of a mixture of the bistrialkyltin oxide and alcohol, R′OH. Under these latter conditions, dibutyltin oxide forms the 1,1,3,3-tetra-butyl-1,3-dialkoxydistannoxanes, (R′O)Bu2Sn·O·SnBu2(OR′), which (except when R = Me) decompose on distillation into the dialkoxide, Bu2Sn(OR′)2, and oxide, Bu2SnO.The temperature at which the n.m.r. coupling between tin atoms and the alkoxy-groups is broken in the alkoxides Bu3SnOR′ shows that the rate of exchange follows the sequence MeO > EtO > PhCH2·O > Me3C·CH2·O, Me2CH·O, PhMeCH·O, Ph2CH·O.

Journal ArticleDOI
TL;DR: In this paper, the photolysis of 3-diazo-1,1,2,2-tetrafluoropropane gives the corresponding carbene in which migration of the difluoromethyl group is the major reaction; other minor products are believed to arise from a cyclopropANE in an excited state, formed by insertion into the γ-CH bond.
Abstract: Photolysis of 4-diazo-1,1,1,2,2,3,3-heptafluoropentane gives heptafluoropropyl(methyl)carbene, in which migration of hydrogen takes place to give 3,3,4,4,5,5,5-heptafluoropent-1-ene in high yield. Migration of fluorine or of the pentafluoroethyl group is not observed. The photolysis of 3-diazo-1,1,2,2-tetrafluoropropane gives the corresponding carbene in which migration of the difluoromethyl group is the major reaction; other minor products are believed to arise from a cyclopropane in an excited state, formed by insertion into the γ-CH bond.The exploration of routes to 2-diazo-1,1-difluoroethane and 2-diazo-1-fluoropropane, and the n.m.r. spectra of a number of compounds containing the CHF2·CF2· group are also reported.

Journal ArticleDOI
TL;DR: Cyclisation reactions based on the readily available 1-(2-nitrophenyl)- and 1-( 2-cyanophenyl)-pyrroles lead to pyrrolo[1,2-a]quinoxalines and pyrrole[1.2]-benzodiazepines, respectively.
Abstract: Cyclisation reactions based on the readily available 1-(2-nitrophenyl)- and 1-(2-cyanophenyl)-pyrroles lead to pyrrolo[1,2-a]quinoxalines and pyrrolo[1,2-a][1,4]benzodiazepines, respectively.

Journal ArticleDOI
TL;DR: In this paper, the use of peptide synthesis of esters for which aminolysis is assisted by a neighbouring group is described, and it is shown that they condense very rapidly even with hindered amino-esters to give high yields of protected dipeptides.
Abstract: Further examples are presented of the use in peptide synthesis of esters for which aminolysis is assisted by a neighbouring group. 2-Pyridyl thiolesters of phthaloyl-, benzyloxycarbonyl-, and t-butoxycarbonyl-amino-acids are described, and it is shown that they condense very rapidly even with hindered amino-esters to give high yields of protected dipeptides. Phthaloyl-L-phenylalanine pyrimidin-2-yl thiolester is also described. No racemisation could be detected when t-butoxycarbonyl-L-valine 2-pyridyl thiolester condensed with L-valine methyl ester, even in the presence of triethylamine. The thiolesters reacted slowly with alcohols, and ethyl O-t-butoxycarbonylglycylglycolate and -DL-lactate were so prepared. In contrast to the usual solvent dependence for the aminolysis of active esters, the rate of condensation of t-butoxycarbonyl-L-leucine 2-pyridyl thiolester with p-anisidine increases when the solvent is changed from dimethyl sulphoxide to dimethylformamide and then to dioxan or ethyl acetate.