Anthony H. Jackson

Applications of high-pressure liquid chromatography and field desorption mass spectrometry in studies of natural porphyrins and chlorophyll derivatives

Mixtures of porphyrins derived from natural sources can be readily separated by high-pressure liquid chromatography both analytically and on a preparative scale. A variety of procedures have been developed not only for the esters but also for free acids, and on the analytical scale quantitation is easily achieved by visible absorption. The retention times are largely characteristic of the number of carboxylic acid side chains (or other polar groups) but further information can be obtained by mass spectrometric studies of the various fractions. Field desorption mass spectrometry is particularly useful for this purpose because the emitter wire can be dipped directly into the eluates. The field desorption spectra of porphyrin free acids and esters as well as their metal complexes give essentially molecular ions with little or no fragmentation in most cases, whereas electron-impact mass spectrometry, particularly of free acids, is impeded by the low volatility of porphyrins. Mixtures can also be analysed by field desorption mass spectrometry, and this provides not only a rapid qualitative assessment of the components of a mixture, but also a check on the subsequent chromatographic separations.

Reactions on solid supports part IV: Reactions of αβ-unsaturated carbonyl compounds with indoles using clay as catalyst☆

Abstract Indoles react with αβ-unsaturated carbonyl compounds in the presence of clay catalysts to give substituted indoles in good yields; in one case a 3-benzyl substituent already present migrated to the 2-position, being displaced by the incoming electrophile, thus confirming that electrophilic substitution in indole occurs primarily at the 3-position.

High-performance liquid chromatographic analysis of porphyrins in clinical materials

Methods for the isolation of porphyrins as their methyl esters from porphyric urine and faeces as well as other biological materials are described. Quantitative analyses can be carried out by high-performance liquid chromatography (HPLC), using appropriate internal standards; hence excretion patterns in the various types of porphyria can be obtained which may facilitate clinical diagnosis more effectively than the earlier qualitative thin-layer chromatographic methods. Use of the newer microparticulate column packing materials has improved the efficiency of the HPLC analyses, and enables the more convenient isochratic elution techniques to be used (rather than gradient elution). Separations of some porphyrin isomers on these columns are also described.

Reactions on solid supports part II: a convenient method for synthesis of pyrromethanes using a montmorillonite clay as catalyst

Abstract α-Acetoxymethylpyrroles couple with α-free pyrroles in presence of Montmorillonite clay to form unsymmetrical pyrromethanes in excellent yields. Symmetrical pyrromethanes were also prepared in a similar manner by clay catalysed self-condensation of α-acetoxymethylpyrroles.

Field desorption mass spectrometry of organometallic complex salts

Abstract The field desorption spectra of [(L)M(CO) 3 ] + BF 4 − [M = Fe, L = cyclo-C 6 H 7 , cyclo-C 7 H 9 , cyclo-C 10 H 11 , 2-MeO-cyclo-C 6 H 7 ; M = W, L = cyclo-C 7 H 7 ], [(Ar)Fe(C 5 H 5 )] + PF 6 − [Ar = C 6 H 6 , CH 3 C 6 H 5 , (CH 3 ) 3 C 6 H 3 ], [(cyclo-C 8 H 11 )Co(C 5 H 5 )] + BF 4 − and [(C 6 H 6 )Cr(CO) 3 ] have been obtained. In all cases molecular or quasi-molecular ions for the cations were present, usually as the base peaks in the spectra. Fragment ions corresponding to metal—ligand cleavages were also found in most cases.

A new modification of the pomeranz–fritsch isoquinoline synthesis

Schiffs bases formed from a variety of alkoxybenzaldehydes and aminoacetaldehyde dimethyl acetal have been hydrogenated to the corresponding benzylamines and converted into N-tosylates. The latter are readily cyclised in dilute mineral acid to isoquinolines in a one-pot reaction; intermediates in this reaction are N-tosyl-1,2-dihydroisoquinolines which can be isolated. N-Benzyl-N-tosylaminoacetaldehyde dimethyl acetal on treatment with dilute acid under the same conditions as for the cyclisation reactions gave N-benzyl-N-tosylaminoacetaldehyde, and then N-tosylbenzylamine; other substituted benzylamino-acetal derivatives similarly when the benzyl group lacked sufficiently activating substituents for cyclisation of the acetal.

Electrophilic substitution in indoles. Part 13. The synthesis and rearrangement of 2-deuteriospiro[cyclopentane-3′-indolenine]

2-Deuterioindole was prepared from N-phenylsulphonylindole by lithiation, quenching with D2O, and hydrolysis. Treatment of the 2-deuterioindole Grignard reagent with succinic anhydride gave 4-(indol-3-yl)-4-oxobutanoic acid with partial loss of the deuterium from the 2-position. 2,3-Dideuterioindole (prepared by acid-catalysed deuteriation of 2-deuterioindole) when treated in the same way, gave the indolyl oxobutanoic acid, 92% deuteriated at the indolyl 2-position. Reduction to the deuterioindolylbutanol and treatment of its toluene-p-sulphonate with potassium t-butoxide give 2-deuterio-spiro[cyclopentane-3′-(3H) indole] which was 88% deuteriated at the 2-position. The kinetics of the acid-catalysed rearrangement of the deuterioindolenine and its non-deuteriated analogue were measured and the ratio kH/kD of the pseudo-first-order rate constants was found to be 1.08, showing that the isotope effect was very small.

Pyrroles and related compounds. Part XXVI. Pyrrole β-keto-esters

Various attempts to synthesise β-keto-esters of pyrroles for use as model compounds, or as intermediates in chlorophyll synthesis, are described. Carboxylation of acetylpyrroles, using dialkyl carbonates or chloroformates, gave a variety of products, including a β-keto-ester and (unexpectedly)N-alkyl- as well as N-alkoxycarbonyl-pyrroles. Attempts to utilise pyrrylacetylenes were unsuccessful, as were direct acylation reactions with derivatives of malonic ester. The most successful approach involved the coupling of a pyrryl acid chloride with the sodium salts of monoalkyl monobenzyl (or mono-t-butyl) esters of malonic acid; the β-keto-diester thus obtained could then be converted (by hydrogenolysis or treatment with cold trifluoroacetic acid) into the desired β-keto-ester.

Alkaloids in seeds of four Erythrina species

Abstract The alkaloids present in the seeds of four Erythrina species, E. brucei, E. cochleata, E. thollonia and E. caribaea have been screened by GC/MS. A new alkaloid, erythrocarine, has been isolated from E. caribaea and characterized as a methylenedioxy analogue of the known dienoid alkaloids erysoline and erysonine.

Reactions on solid supports part I: Novel preparation of α-formyl pyrroles from α-methylpyrroles by oxidation with thallium (III) nitrate on clay

Abstract Treatment of α-methylpyrroles with thallium (III) nitrate/Montmorillonite clay affords the corresponding α-formylpyrroles in excellent yields.