Aziridine structure

An acid-soluble polymer, Montrek, has been produced by the ROP of ethyleneimine, aziridine (structure 5.28). The monomer is a carcinogen so care is taken to remove unreacted monomer. 

By treating norbornene with benzenesulfonyl azide in benzene at room temperature, a crystalline product is obtained in quantitative yield.264-265 On the basis of chemical and nmr evidence, an aziridine structure (85) similar to exo-2,3-epoxy-norbornene (86) is attributed to the adduct. The addition thus occurs at the least hindered exo side of the bicyclic nucleus. 

The transition metal-mediated nitrenoid transfer to olefins represents a very concise route to the aziridine structure very often, however, an excess of the olefinic substrate is required for preparatively useful yields. In this arena, Andersson and co-workers have studied the copper-catalyzed aziridination of olefins using [A -(arenesulfonyl)imino]phenyliodinanes 446 as nitrene precursors, and have reported on conditions which give good to excellent yields of aziridines 447 without the constraint of having to use an excess of alkene (Scheme 116). 

General name for antitumor antibiotics with benzo-quinone and aziridine structural units from cultures of streptomycetes (e. g., Streptomyces lavendulae, S. ver-ticillatus, S. caespitosus). There are more than 15 natural variants containing a pyrrolo) 1,2-a)indole system and differing in R and R, with OH in place of OCHj at C-9a, and different stereochemistries at C-9. The violet to blue-violet, optically active M. crystallize readily and are soluble in water, methanol, and acetone. A cluster of 47 bacterial genes that control biosynthesis of M. C has been characterised. The biosynthetic building block of the benzoquinone (C7N) unit is 3-amino-5-hydroxybenzoic acid, several total syntheses have been repotted. 

Aziridines represented by the general structure (458 X = 0, S, NR) undergo a facile ring opening and subsequent closure on heating with sodium iodide in acetone or acetonitrile. For (458 X = O) the oxazoline (460) was formed, presumably via the intermediate (459) (66JOC59). 

Equilibration of aziridines via azomethine ylides has been reported for a variety of structures (67JA1753). Most aziridines equilibrated by this method show greater cis stability. An energy barrier has been detected between the two isomeric azomethine ylides (69AG(E)602>. 

Gabriel synthesis, 7, 33 aziridines, 7, 81-82 thiazoles, 6, 302 Galanthamine structure, 4, 548 Galbacin NMR, 4, 574 Gelatin hardeners for... 

The oxidation of certain steroidal <5,e-unsaturated amines with either N-chlorosuccinimide or lead tetraacetate yields bridged aziridines, see structure (117)... 

A comparison between aziridine 4, as a model of nonaromatic structure, l//-azirine lb, l//-diazirine 2b, and triazirine 3 using 6-31G /MP3 calculations leads to the following values for the N-H inversion barriers 4, 86.2 (experimental value 80 kJ mol ) lb, 190.4 2b, 160.2 and 3, 246 kJ mol [89JCC468].Tlie difference in inversion barrier values between lb and 2b was attributed to a decrease in the antiaromaticity of the latter. Tire antiaromaticity of lb was examined subsequently by the same authors [89JST(201)17]. 

Only one report is concerned with the synthesis, molecular structure, and X-ray analysis of this ring system as 2 (86KGS477). The synthesis of 2 was achieved by the cyclization of 2-aziridine carboxylic acid hydrazide with acetone as shown in Scheme 2. 

Epoxides are found in thousands of biological molecules and constitute vital functional entities. They can impart localized structural rigidity, confer cytotoxicity through their role as alkylating agents, or act as reactive intermediates in complex synthetic sequences. The widespread occurrence of epoxides is contrasted by only a handful of aziridines that are known to date. In this chapter we would like to introduce the different mechanisms by which enzymes produce epoxides. 

Very recently, the Shipman group have made a further step towards a comprehensive structure/activity profile for noncovalent interactions between azinomycin B and DNA [152]. They synthesized simplified azinomycin analogues 69 and 96-98 (Scheme 11.13), retaining both the epoxide and aziridine alkylating functionalities, with systematically altered substitution on the naphthoate fragment, and analyzed their DNA crosslinking by gel electrophoresis. They found that cross-... 

The tightly bound chromophore could be extracted from the protein with methanol [186], and the major component of the extract was determined to have the enediyne structure 116 (Figure 11.21), related to chromophores of other chromoprotein antitumor agents such as neocarzinostatin. Additional minor components were extracted, variously containing an OH group instead of OMe attached to the enediyne core, with Cl instead of OMe when chloride was present in the buffer salt, or with OEt instead of OMe when ethanol was used for the extraction. Another byproduct was isolated in the form of structure 117, consistent with a facile cy-doaromatization reaction as observed for all other enediyne antibiotics. Surprisingly, 117 also displayed antibiotic and antitumor activity, perhaps due to alkylation of DNA or protein by the aziridine. The interpretation of these results was that 116 and the other enediyne byproducts were merely artifacts of the extraction procedure and that the true structure of the maduropeptin chromophore is the aziridine 118. 

The reaction used to test these solid catalysts was the aziridination of styrene with AT-tosyliminophenyliodinane (Phi = NTos) (Scheme 10). In most cases, enantioselectivities were low or moderate (up to 60% ee). The loss of enantioselectivity on changing from ligand 11a to ligand 12 was attributed to the fact that ligand 12 is too big for the copper complex to be accommodated into the zeolite supercages. Further studies carried out with hgands 11a and 11b [62] demonstrated that the reaction is more enantioselective with the supported catalyst (82% ee with 11a and 77% ee with 11b) than in solution (54% ee with 11a and 31% ee with 11b). This trend supports the confinement effect of the zeolite structure on the stereoselectivity of the reaction. 

With aziridine, nitrogen pentoxide forms a compound that is very unstable and is thought to have the following structure ... 

Reactive structures that interfere with the biochemical assay (aldehydes, acyl-halides, sulfonyl-halides, Michael acceptors, epoxides, aziridines, oximes, N-oxides). 

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