General Studies

Carbon-13 n.m.r. assignments have been reported for a number of isomeric 3-butyl-5-methyloctahydroindolizines that were synthesized in studies of the trial pheromone of the Pharaoh ant, and for some closely related indolizidines. This work includes a detailed discussion of the preferred conformations of these compounds.15 Securinegine, a minor alkaloid from Securinega suffruticosa Rehd., is isomeric with securinine, and the structure (22) has been proposed.16 

Iwashita, M. Suzuki, T. Kusumi, and H. Kakisawa, Chem. Lett., 1980, 383. 

Separation of mono- and di-ester pyrrolizidine alkaloids has been achieved by ion-pair adsorption t.l.c., using chloride (or iodide) as the counter-ion.48 Chloranil has been used to oxidize pyrrolizidine alkaloids on t.l.c. The pyrrole derivatives that were formed were then detected with Ehrlich s reagent49 or sulphuric acid.50 Mixtures of pyrrolizidine alkaloids have been separated by h.p.l.c. on a reversed-phase styrene-divinylbenzene resin.51 In a sensitive method for the detection of pyrrolizidine alkaloids, the protonated alkaloids were complexed with aqueous methyl orange. The dye was then released from the complex and estimated spectrophotometrically.52 

Indicine JV-oxide (53) is an anti-cancer drug that is now undergoing clinical trials. Methods for its estimation include oxidation to the pyrrole derivative and treatment with Ehrlich s reagent,53 g.l.c. analysis of its trimethylsilyl derivatives,54 and differential pulse radiography.55 The aqueous degradation of indicine iV-oxide (53) to retronecine /V-oxide and (—)-trachelanthic acid has been studied.56 Indicine jV-oxide is reduced to indicine by Fem, by reduced cytochrome c, by ascorbic acid, and by denatured haemoglobin.57 

Further 13C n.m.r. spectral data on pyrrolizidine alkaloids have been reported,58 including a re-assignment for the signals due to C-7 and C-8 in monocrotaline (48) and retronecine (27).59 This re-assignment is supported by 13C n.m.r. spectra that were obtained after biosynthetic enrichment of retronecine with 13C.60 

Australian workers have prepared a number of semisynthetic pyrrolizidine esters as part of a major investigation of pyrrolizidine alkaloid toxicity. 7,9-Diacetylheliotridine (52), 7-acetylheliotridine (53), 7,9-divalerylheliotridine (54), and 7-pivalyl-(55), 9-pivalyl-(56) and 7,9-dipivalylheliotridine (57) were prepared by acylation of heliotridine with the appropriate acid chloride. The three last- 

Klasek, V. A. Mnatsakanyan, and F. Santavy, Coll. Czech. Chem. Comm., 1975, 40, 2524. 

Tritium-labelled disenedoylretronedne (64) required for studies of the biological properties of pyrrolizidine alkaloids, has been prepared by acylation of [9- H2]retronedne by senedoyl chloride. The label was introduced into retronedne following the Corey method of oxidation of the primary allylic alcohol function of unlabelled retronedne (65) with manganese dioxide in the presence of potassium 

Semisynthetic amides of retronamine (66), itself prepared from retronecine (65) in three steps, have been synthesized by coupling with the appropriate acid using AW -dicyclohexylcarbodi-imide. Several of the compounds prepared, notably the p hydroxy benzoyl-, cinnamoyl-, and benzoyl-retronamines, had marked hypotensive activity. The amides could not be crystallized and details of their characterization were not given. Atal and his co-workers have also prepared - a number of semisynthetic diesters of retronecine, heliotridine, and platynedne by esterification of the necine base with the appropriate acid chloride. Several of the compounds prepared had marked local anaesthetic activity. 

Russian workers have prepared for pharmacological studies simple carbamates of trachelanthamidine (68) by treatment with the appropriate isocyanate. Some cholinesterase inhibitors based on the standard decamethonium model have been prepared. Decamethylene bistrachelanthamine dibromide (69) showed marked curare-like activity in cats and rabbits. New procedures for the iodometric determination of platyphylline bitartrate and for the colorimetric determination of trichodesmine and incanine in the organs of poisoned animals have been described. 

Separation of pyrrolizidine alkaloid mixtures has been carried out 

This technique has now been extended for use on h.p.l.c., and the alkaloids from comfrey (Symphytum spp.) were separated. Diastereoisomeric pyrrolizidine alkaloid monoesters containing a vicinal diol were previously separated as their borate complexes (cf. Vol. 12, p. 62). Related diastereoisomeric alkaloids have 

The high-resolution p.m.r, and ester alkaloids have been recorded. 

Stoeckli-Evans. Like all 11-membered macrocyclic diesters of retronecine except trichodesmine (45), the ester groups are syn-parallel and directed below the plane of the macrocycle. X-Ray 

spectral assignments have been made for a number of pyrrolizidine alkaloids, including retronecine (51), platynecine, heliotrine, supinine, lasiocarpine, crispatine, monocrotaline (54), madurensine, and retror-sine. Some of the assignments reported for retrorsine have been revised. A H n.m.r. spectroscopic method for determination of the amount of pyrrolizidine alkaloids present in the extracts of small samples of a number of Senecio species 

Deinzer, P. Thomson, D. Griffin, and E. Dickinson, Biomed. Mass Spectrom., 1978, 5,175. 

R = H or COCH=CMe Reagents i, Activated MnOj ii, NaB H4 iii, Me2C=CHCOCl 

Metal carbonyl reactions in supercritical fluids have emerged in recent years as a valuable technique for producing some interesting species. The pioneering work in this field has been carried at the University of Nottingham by Poliakoff and co-workers and, in 2000, they continued their expansion of the technique to 

Finishing off this section we can report on various reactions of penta-fluorohalobenzenes with transition metal carbonyl anions  

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If the medium is sufficiently basic to generate the arabident anion 31. mixtures of products resulting from N-nng and N-exocyclic reactivity are observed. Here again steric effects can preferentially orient the whole reaction toward one of the two nitrogens. A general study clearly delineating the rules of behavior for 31 accordine to the nature of R. the... 

Amino-4-phenylthiazole when heated with Raney Ni is reported to yield acetophenone (469). In the course of a general study on reductive cleavage in heterocyclic systems Hoff et al. studied the reaction of 2-amino-4-methylthiazole with Na in liquid ammonia. Two equivalents of Na are necessary to obtain a mixture of 4-methyl-3-thiazoline (240) and... 

Apart from the general study by Wait and Wesley on azanaphthalenes, including most of the pyridopyridazines (66JSP(19)25), more specialized studies have attempted to relate charge density calculations to various chemical and physical properties, with greater success in the latter case. 

Dtpartrnent of Chemistry, School of General Studies, The Australian National University, Canberra, A.C.T., Australia... 

Reviews and General Studies Dealing with Tautomeric Studies of Heterocyclic Compounds... 

A detailed study of spectra of compounds 1, 2, and 3 has been published as part of a general study of azolopyridines (84OMR209). The shifts are shown in Table III. The N shifts have been used to determine the structure of 7-amino-triazolopyridines 128 and 129 (89T7041). The shifts recorded were 56.8, 56.2 (Nl), 245.4, 246.3 (N2), 320.6, 316.8 (N7a), all from nitromethane as standard at 380 ppm the absorption for the amine was at 345.5, 350 ppm in accordance with the amino structure shown, rather than the imino forms 128a and 129a. 

The fact that the absolute magnitudes of these two sets of coupling constants are different is also expected on the basis of the Pople, Bothner-By treatment (48). It would clearly be of some considerable interest if a general study were to be made of the stereospecificity of this geminal dependence since this may lead to another method for determining carbohydrate conformations. 

A general study of the reduction of acetone to pinacol. Calvert, India Rubber Rev. 26, No. 9, 48 (1926). 

These are chemically independent of Eqs. (11-51) and (11-52). Each follows in time after the quenching event. The back reactions do not involve luminescent quenching, and so they are generally studied by absorption measurements. In these cases the values17 are 53 = 5 x 106 Lmol-1 s-1 and 54 = 4.5 X 107 Lmol-1 s-1. 

The oxidation of lactate ion by alkaline permanganate (0.1 M base) was examined as part of the general study of the oxidation of acetone and its possible oxidation products . The reaetion is first-order in lactate ion, and, if it is assumed that it is also first-order in oxidant, then the second-order rate coefficient is 2 l.mole sec" at 25 °C. 

The crystallization step is generally studied quite exhaustively at the laboratory scale and often at the pilot scale. The reaction chemistry should be properly understood to access effects, if any, of the synthesis step on the impurity profile. In batch cooling crystallizers attempts have been made to create optimum conditions by on-line turbidity analysis (Moscosa-Santillan et al., 2000). Physicochemical characterization of the products should be done rigorously (Tanguy and Marchal, 1996). 

TABLE 1. Results of stimulus generalization studies using racemic DOM as... 

One of the primary bases for the hypothesis that allelochemicals affect mineral uptake rests with the fact that the concentration of minerals In receiver plants can be altered by donor plants by a mechanism other than competition for minerals. In general, studies In support of this hypothesis have Involved measuring the amount of mineral present per weight of a particular plant part following absorption of minerals by the roots of the Intact receiver. 

In a more general study it has been reported that epoxy formates can be employed for the preparation of hydroxy lactols as shown in Scheme 30. Other esters failed to give the desired products, though [121]. 

A general study, but with many references to alchemy... 

Classification of bacterial viruses In the bacterial viruses, a formal classification scheme is rarely used. Rather, each bacterial virus is designated in terms of its principal bacterial host, followed by an arbitrary alphanumeric. Thus, we speak of T4 virus of Escherichia coli or P22 virus of Salmonella typhimurium. An overview of some of the major types of bacterial viruses is given later. We should note, however, that although a bacterial virus may be designated in reference to its principal host, the actual host range of the virus may be broader. Thus, bacteriophage Mu, generally studied with Escherichia coli, also infects Citrobacter and Salmonella. 

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