David R. Taylor

Chromenes from Eupatorium riparium

Abstract Jamaican E. riparium Regel has been examined and found to contain the new chromene acetovanillochromene (6-acetyl-8-methoxy-2,2-dimethylchromene) as well as methyl-ripariochromene A (6-acetyl-7,8-dimethoxy-2,2-dimethylchromene) previously isolated from an Australian sample of the same species. Confirmation of the structure of methylripariochromene A is reported.

Identification of endogenous gibberellins in strawberry, including the novel gibberellins GA123, GA124 and GA125

Extracts of carboxylic acids from immature fruits of strawberry (Fragaria x ananassa Duch. cv. Elsanta) were analysed for gibberellins by combined gas chromatography-mass spectrometry. The following previously characterised gibberellins were identified by comparison of their mass spectra and Kovats retention indices (KRIs) with those of standards or published data: GA1, GA3, GA5, GA8, GA12, GA17, GA19, GA20, GA29, GA44, GA48, GA49, GA53, GA77, GA97, GA111 and GA112. Evidence for endogenous 1-epi GA61 (GA119) and 11alpha-OH-GA12 was also obtained. In addition, a number of putative GAs were detected. Of these, three were shown to be 12alpha-hydroxy-GA53, 12alpha-hydroxy-GA44, and 12alpha-hydroxy-GA19 by comparison with authentic compounds prepared by rational synthesis, and have been allocated the descriptors GA123, GA124 and GA125, respectively.

N-methylflindersine from Spathelia sorbifolia

Abstract The isolation and taxonomic significance of N -methylflindersine from S. sorbifolia is discussed.

Serum Beta-aminopropionaldehyde: identification and origin

Abstract 1. 1. β-Aminopropionaldehyde is one of the serum aldehydes whose level increases on treating serum with As2O3 and methanol. 2. 2. In animal tissues, β-aminopropionaldehyde can arise directly from the oxidation of spermidine or diaminopropane. 3. 3. A pathway linking spermidine, β-aminopropionaldehyde and malondialdehyde to the control of RNA and DNA synthesis is proposed.

Thiadiazoles and thiadiazolines. Part 1. Reaction of thiourea and ethylenethiourea with chlorodiazabutadienes: a new route to 4-amidino-1,3,4-thiadiazolines

1-Chloro-1,4-diaryldiazabutadienes (1) react with thiourea to give hydrochlorides of 4-amidino-2,5-diaryl-Δ2-1,3,4-thiadiazolines from which the corresponding free bases (2) are obtained by treatment with cold alkali. Imidazolidine-2-thione (ethylenethiourea) reacts similarly with the chlorodiazabutadienes (1a,b) to give, after treatment with cold alkali, 4-(4,5-dihydroimidazolin-2-yl)-2,5-diaryl-Δ2-1,3,4-thiadiazolines (6a,b). In the presence of an excess of sodium borohydride the reaction of (1a) with thiourea yielded some N2-benzylthiobenzoylhydrazine (12), compatible with the capture of an intermediate iminium ion. A mechanism is suggested for these reactions.

Unsaturated compounds containing nitrogen. Part 5. Reactions of 1,4-dichloro-1,4-diphenyl-2,3-diazabutadiene with nucleophiles

1,4-Dichloro-1,4-diphenyl-2,3-diazabutadiene (1) reacts with potassium cyanate to give 5-phenyl-1,2,4-triazol-3(2H)-one (9), but with potassium thiocyanate it gives the 1-chloro-4-thiocyanato-2,3-diazabutadiene (3). The thiocyanate (3) is not isomerized by heat, but is hydrolysed by acid to a mixture of 2,5-diphenyl-1,3,4-oxadiazole and 2-amino-5-phenyl-1,3,4-thiadiazole. Sodium hydrosulphide, potassium ethylxanthate, and thiourea all convert the dichlorodiazabutadiene (1) into 2,5-dipheyl-1,3,4-thiadiazole, while 2-aminobenzenethiol converts it into 2-phenylbenzothiazole.

Thiadiazoles and thiadiazolines. Part 3. Synthesis of triazol-3-yl-Δ2-1,3,4-thiadiazolines and a new synthesis of unsymmetrical 2,5-di-substituted 1,3,4-thiadiazoles

The reaction of 1-chloro-1,4-diphenyl-2,3-diazabutadiene (1) with 1-acetyl- and with 1-benzoyl-thiosemicarbazide yields initially the hydrochlorides of N2-acetyl- and N2-benzoyl-Δ2-1,3,4-thiadiazoline-4-carboxamide hydrazone (4a, b) which are converted by aqueous sodium hydroxide into the corresponding free bases (5a, b) and thence by cyclodehydration into 4-(4H-1,2,4-triazol-3-yl)-Δ2-1,3,4-thiadiazolines (6a, b). Treatment of (1) with thioacetamide, thionicotinamide, or the thiobenzamides 4-XC6H4CSNH2(where X = H, MeO, and Cl), leads at 20–95 °C to 2-phenyl-5-R-1,3,4-thiadiazoles (9a–e)(where R = Me, 3-pyridyl, or 4-XC6H4). The reaction of (1) with guanidine leads, via the hydrochloride, to 3-amino-5-phenyl-4H-1,2,4-triazole. The mechanism of these and related reactions of (1) with other S-nucleophiles are discussed.

Polyhalogeno-allenes and -acetylenes. Part 15. Dipolar cycloadditions of N-phenylsydnone and aryl azides to perfluoropropadiene and perfluoropropyne

N-Phenylsydnone reacts with perfluoropropadiene to give 3-fluoro-1-phenyl-4-trifluoromethylpyrazole (2), anionotropic rearrangement following the dipolar cycloaddition; with perfluoropropyne, giving a 1 : 2 mixture of (2) and the isomeric 4-fluoro-1-phenyl-3-trifluoromethylpyrazole (3); and with perfluorobut-2-yne to give the homologue 1-phenyl-3,4-bis(trifluoromethyl)pyrazole (4). Phenyl azide and perfluoropropadiene react at 50 °C to give a 9 : 1 mixture of 4-fluoro-1-phenyl-5-trifluoromethyl-1,2,3-triazole (5) and 5-fluoro-1-phenyl-4-trifluoromethyl-1,2,3-triazole (6), also by consecutive cycloaddition and anionotropic rearrangement. The minor isomer, believed to be compound (6), was the only adduct isolated by similar treatment of perfluoropropyne. Perfluoropropadiene and pentafluorophenyl azide react slowly to give a low yield of an adduct believed to be 4(or 5)-fluoro-1-pentafluorophenyl-5(or 4)-trifluoromethyl-1,2,3-triazole. The orientations of these additions are discussed in terms of the frontier orbitals involved.

Ene reactions of allenes. Part 5. Regio- and stereo-selective ene reactions of a trialkylallene

Thermal ene insertion reactions have been achieved between 2-methylpenta-2,3-diene and the reactive enophiles diethyl azodiformate, hexafluorobut-2-yne, dimethyl acetylenedicarboxylate, and 1,3-dichlorotetrafluoroacetone. In each case the ene adduct isolated arises by regioselective attack at the more substituted allenic π-bond, and the 1H n.m.r. spectra of the adducts also suggest that the reaction is stereoselective. Whereas the azodiformate converts the allene cleanly to the dienyldicarbamate (1d), the other enophiles also cause numerous side-reactions to occur, leading to the formation of [2 + 2] cycloadducts, rearrangement of the allene to 2-methylpenta-1,3-diene, and Diels–Alder cycloaddition. Related reactions between dichlorotetrafluoroacetone and 2,4-dimethylpenta-2,3-diene and 3-methylbuta-1,2-diene, and between hexafluoroacetone and 2,4-dimethylpenta-2,3-diene are discussed.

New chromones from Spathelia sorbifolia L. (Rutaceae); synthesis of the benzo[1,2-b:3,4-b′]dipyranone sorbifolin

Ten more chromones containing both 2,2-dimethylchromen and 2-methylchromone entities, all derivatives of 5,7-dihydroxy-2-methylchromone, have been isolated from Spathelia sorbifoliaL. and characterised. These are allopteroxylin (6), spatheliachromen (9), spatheliabischromen (4), methylallopteroxylin (8), methylsorbifolin (2), methylisospatheliachromen (19), anhydrosorbifolin (33). 6-(3-methylbut-2-enyl)allopteroxylin (28), 10-(3-methylbut-2-enyl)spatheliachromen (21), and 10-(3-methylbut-2-enoyl)spatheliachromen (23). Sorbifolin (1) has been synthesised via the reaction of singlet oxygen with the acetate of (28).